System, apparatus and / or process

Abstract

A process for remote localization of an object including: receiving / determining two or more measurements of magnetic fields using at least one magnetometer when the magnetic fields are generated by at least one magnetic field source from two or more respective source locations, when the or each magnetic field source is remote from the or each magnetometer which is in / on an opaque medium; receiving / determining the two or more respective source locations of the magnetic field source in three orthogonal dimensions by determining locations of the magnetic field source when the magnetic field measurements are / were determined; and numerically estimating a location of the magnetometer in three orthogonal dimensions using: the two or more magnetic field measurements; the two or more respective source locations; and a mathematical model representing a magnetic dipole of the magnetic field source.

Description

SYSTEM, APPARATUS AND / OR PROCESSRELATED APPLICATION

[0001] The present application is related to Singapore Patent Application No.10202400375X, entitled “System, Apparatus and / or Process”, in the name of Orica International Pte Ltd, filed 9 February 2024, the as-filed documents of which, including the patent specification, are hereby incorporated by reference in their entireties.TECHNICAL FIELD[0002| The present disclosure relates to localization of objects, e.g., buried / submerged / obscured markers, including determining their locations in three orthogonal dimensions, thus determining "3D locations".BACKGROUND

[0003] It is often desirable to monitor movement of portions of an opaque / non-transparent medium, including substantially solid materials (e.g., in commercial blasting / mining / quarrying operations), or to localize buried / submerged / obscured objects (e.g., in commercial blasting / mining / quarrying / exploration operations and / or in safety / rescue / monitoring operations).

[0004] In an example, identification of ore / waste boundaries is a common, and, usually necessary, part of recovering valuable minerals as part of the mining process that serves two primary purposes: firstly, it ensures that ore loss is minimised at the excavation stage; secondly, it ensures that the treatment of waste is minimised in the post-mining recovery stage. To this end, physical targets have been used to track the boundaries after blasting.These targets include visual markers such as plastic pipes installed in extra boreholes withinand along the boundaries, or coloured sandbags; magnetic metal targets such as metal balls, chains and the like that are picked up using simple metal detectors. In some mines a spotter is required to assist the operator to make that decision - a further, albeit small, cost impost on the operation. In other examples, geotechnical monitoring may be desirable to monitor movements in dam walls and / or coal stockpiles, and borehole monitoring may be desirable to monitor / detect locations of boreholes (including at different depths in the boreholes) in mining / quarrying operations. Some previous movement markers may have been designed to generate and emit a magnetic field that penetrates the medium around the markers (e g., ore / rock / earth), and that is detectable at an adjacent surface of the medium (e g., at the surface of a muckpile after blasting), and a handheld magnetic-field detector may have been used to detect a point on the surface of maximum strength of the magnetic field, and thus to estimate that the buried marker was located directly below / adjacent that point. When used for commercial blasting operations, these markers may be referred to as "blast movement markers". However, some previous markers used for localization may be too complicated / expensive for some applications, and previous processes for determining their locations may be too slow / inaccurate. Some previous markers may require detection of a magnetic field maximum in the horizontal x-y plane relative to gravity (of the surface in which the marker is buried) by moving a detector (e.g., a sensor loop) back and forth in the horizontal place, and such previous markers require a self-righting antenna inside to provide a vertical magnetic dipole (VMD) relative to gravity that produces a symmetrical magnetic field, such that the magnetic field maximum will be directly above it. Previous markers may require separate determination of marker depth (in the vertical z direction), e g., by angling the sensor loop to measure the angle of the field lines (null-finding), which may require manual operation of the detector to: (i) move it horizontally back-and-forth over the maximum, and (ii) then angle it relative to the horizontal to find the field line angles; after which the depth can be estimated / determined from the field line angles Alternatively, previous markers may need to be placed at the same elevation / depth when multiple markers are used, which may be difficult to arrange and / or inaccurate. The previous markers with the internal self-righting mechanisms may be prone to failure or poor operation in some environments, thus introducing localization errors.

[0005] In another example, in commercial blasting operations for mining / quarrying, including underground mining, it may be desirable to confirm the locations of buried explosive initiators / primers, particularly initiators / primers configured for wireless through- the-earth (TTE) operation, such as Orica's WEBGEN devices. International Patent Application Publication No. W02015 / 143500A1 (Appleby et al.) describes a method for remote localization of a marker TTE; however, this method may require an undesirably complicated / expensive marker to be integrated / attached to an explosive initiator / primer, and / or an undesirably large / powerful magnetic field source, at least for some operations.

[0006] In another example, it may be desirable to mark where buried objects are located to mitigate undesirable / dangerous activities, e.g., excavation, including to mark buried pipelines / powerlines or to mark buried explosive initiators / primers / material. Previous markers for marking buried pipeline locations may require a person using a handheld metal detector to locate the markers (e.g., and thus the pipeline) using an iterative search, which might be too slow / inconvenient for some applications.

[0007] In another example, in seismic exploration, it may be desirable to localize the blasting initiators / primers (also referred to as "sources") and / or the geophone / hydrophones (also referred to as "receivers"). Previous markers for seismic sources / receivers may include global positioning system (GPS) receivers for localization; however, these may be insufficiently accurate / useful in GPS-denied environments, e.g., in water / earth or under foliage.

[0008] In another example, in agricultural operations, it may be desirable to monitor soil conditions using localized sensing devices. Previous methods for soil monitoring may have required soil samples to be taken from selected / surveyed locations, and the locations recorded manually to match laboratory testing results on the soil samples.

[0009] In another example, in emergency operations, it may be desirable to locate and / or track a person or a piece of equipment buried in an avalanche, a landslide, or a collapsed structure.

[0010] In another example, in civil engineering and construction operations, it may be desirable to locate and / or track a person or a piece of equipment inside a structure; and in geological, seismological or construction monitoring, it may be desirable to monitor rock, earth, foundations or structures to determine movement over time.

[0011] It is desired to address or ameliorate one or more disadvantages or limitations associated with the prior art, or to at least provide a useful alternative.SUMMARY

[0012] Disclosed herein is a process (300) for remote localization of an object, the process (300) including: a. receiving / determining two or more measurements ("magnetic field measurements") of magnetic fields using at least one magnetometer (106) when the magnetic fields are generated by at least one magnetic field source(105) from two or more respective source locations, when the or each magnetic field source (105) is remote from the or each magnetometer (106) which is in / on an opaque medium (104) such that the magnetic fields (b) penetrate through the medium (104) and / or through a navigable medium (112) (e.g., space, air or water) between the or each magnetic field source (105) and the or each magnetometer (106) (the opaque medium (104) may have a surface, e.g., including earth / rock / ice / water, and the or each magnetometer(106) may be buried or submerged in the medium (104) or seated / placed on the opaque medium (104) such that the magnetometer (106) is stationary relative to the opaque medium (104) and so that the magnetometer (106) moves with the medium (104) if the medium (104) moves); b. receiving / determining (and / or measuring / recording) the two or more respective source locations (also referred to as "source stations") of the magnetic field source (105) in three orthogonal dimensions (3D) by determining locations of the magnetic field source (105) when the magnetic field measurements are / were determined (wherein the source locations may bein the opaque medium (104), or outside the opaque medium (104) and in the navigable medium (112)); and c. numerically estimating (e.g., using an iterative process, and using at least one data processing unit / processor, such as at least one microprocessor) a location ("marker location") of the magnetometer (106) in three orthogonal dimensions (3D) using: i. the two or more magnetic field measurements; ii. the two or more respective source locations, and iii. a mathematical model representing a magnetic dipole of the magnetic field source (105).

[0013] The magnetic fields (b) may be generated while the magnetic field source (105) is a mobile magnetic field source attached to at least one mobile platform (108) (which can include a plurality of configurations, including one or more magnetic field sources attached to the or each mobile platform (108), and / or two or more mobile magnetic field sources attached to two or more mobile platforms (108), including one mobile magnetic field source attached to each mobile platform (108)), including using magnetic field measurements made while a speed of the or each mobile magnetic field source is substantially non-zero (in a reference frame of the magnetometer (106) and the opaque medium (104)). The mobile platform (108) is configured to move relative to the magnetometer (106) and the opaque medium (104). The mobile platform (108) is configured to move in the opaque medium (104) and / or outside the medium (104), which may include on the surface of the medium (104) (e g., for earth / rock / ice or water) and / or flying / floating substantially off the surface — e.g., above a mine bench or along a mine tunnel. The magnetic field measurements are made while the mobile magnetic field source is travelling along a path including the source locations. The substantially nonzero speed can include from slightly above zero meters per second (m / s) to substantially 30 m / s, including from above zero to 25 m / s, including from above zero to substantially 3 to 4 m / s (e.g., for a multi-rotor drone, e.g., for mining or quarrying operations), and substantially 8 m / s to substantially 25 m / s (e g., for a fixed wing drone, e.g., for linear operations, e.g.,along a ditch or pipeline). Using the one or more mobile platforms (108), e.g., in the form of one or more remotely controlled and / or autonomous vehicles (referred to as "drones"), including an individual drone or a plurality of such vehicles (referred to as a "drone swarm"), allows rapid / convenient coverage of multiple of the source locations (also referred to as "stations") as the mobile platforms (108) move.

[0014] The magnetic fields (b) may be generated while the magnetic field source (105) is a stationary magnetic field source attached to a fixed point, or stationary at a fixed point, which is a non-mobile point in a reference frame of a site that includes the at least one opaque medium (104) and the magnetometer (106), which may be a mine frame of reference, or a site frame of reference, or an environment frame of reference. The fixed magnetic field source mitigates the need to measure the location of at least one of the magnetic field sources (105) while the magnetic field measurements are being made, e.g., because the location of the fixed point can be selected / measured before / after the magnetic field measurements are being made.

[0015] As the magnetometer (106) is in or on the marker apparatus (102), the (estimated) magnetometer (106) location is also an (estimated) marker location, or at least the magnetometer (106) is in or at the marker location.

[0016] The process (300) allows the magnetometer (106) to have any orientation in the medium (104) (i.e., an arbitrary orientation, e.g., caused by movement of the medium (104)) while still being accurately localizable, thus addressing problems of expen si ve / unreli able internal self-righting mechanisms in buried markers. The marker apparatus (102) and the magnetometer (106) remains stationery during the two or more measurements (e g., by being buried), with a fixed location and orientation, with respect to the duration of the two or more measurements. Using the mobile magnetic field source attached to the mobile platform (108) may be more flexible / efficient that using only an array of fixed magnetic field sources, fixed in space, e.g., at fixed stations relative to a mining site.

[0017] Use of the mathematical model allows localization of the marker apparatus (102), and a plurality of marker apparatuses (102) with respective magnetometers (106), at the same time, without requiring detection of a signal maximum from each separate marker apparatus (102) on the surface or in space, thus without requiring the mobile platform (108) to passthrough a region of space containing a maximum of the antenna pattern of the magnetometer (106) of the marker apparatus (102). This may allow for efficient / flexible routing of the mobile platform (108) around a site with one or more of the marker apparatuses (102). The mathematical model includes relationships between the magnetometer location (and thus a corresponding 3D marker location) and the magnetic field measurements and source locations, thus allowing a "one-step solution" of the 3D marker location, rather than estimation of an XY location from a maximum signal and a separate estimation of a Z (depth) location from knowledge of ground permeability as in prior methods. As the process (300) uses the mathematical model for determining the magnetometer (106) location, the process (300) may be referred to as providing "model-based localization" As the process (300) determines the magnetometer (106) location in 3D without requiring knowledge of previous locations of the magnetometer (106), the process (300) can use the magnetic field measurements taken after a blasting operation, including when the marker apparatus (102) is in a post-blast muckpile.

[0018] Use of the mathematical model allows localization of the marker apparatus (102) in three orthogonal dimensions (3D location) without necessarily requiring knowledge of a sensitivity of the magnetometer (106), or an orientation of the magnetometer (106), and may avoid a factory calibration of the magnetometer (106) or alignment of antenna coil(s) to a shell (714) of the marker apparatus (102).

[0019] The combination of the magnetic strength and the orientation of the magnetic field source (105) defines its magnetic moment.

[0020] The process (300) may include numerically estimating (e.g., using the iterative process) an orientation of the magnetometer (106), including in three orthogonal dimensions (3D orientation), and estimating an orientation of the marker apparatus (102) (in / on the medium) from the numerically estimated orientation of the magnetometer (106).

[0021] The process (300) may optionally include using a selected strength or moment or a calibration of the magnetic field source (105) to improve precision. The magnetic field source (105) may be configured to generate the magnetic fields (b) with a selected strength or moment, which may include a selected value and / or a selected range of values (which may bereferred to as a "calibrated range"), and the process (300) may use the selected strength or moment with the mathematical model when numerically estimating the location of the magnetometer (106).

[0022] The process (300) may optionally include using a selected sensitivity (K) of the magnetometer (106) to improve efficiency of the localization. The magnetometer (106) may be configured to measure the magnetic fields (b) with a selected sensitivity (e.g., represented by K or K herein, where K in general includes a 3x3 matrix since the magnetometer (106) can be a 3-axis magnetometer where the alignment / orthogonality of the axes is also calibrated). The magnetometer sensitivity (K) may include a selected set of values and / or a selected range of values (which may be referred to as a "calibrated sensitivity range") based on the factory calibration and / or calibration measurements. The process (300) may use the sensitivity (K) with the mathematical model when numerically estimating the location of the magnetometer (106).

[0023] The marker apparatus (102) may be configured to measure / control the orientation of the magnetometer (106), and the process (300) may use the measured / controlled orientation of the magnetometer (106) with the mathematical model when numerically estimating the location of the magnetometer (106), which may improve the efficiency / precision of the process (300).

[0024] The process (300) may include: a. receiving / determining (and / or measuring / recording or controlling) one or more orientations (each being in ID to 3D, e g., depending on the type of the magnetometer (106)) of the magnetometer (106) in three orthogonal dimensions (3D orientation) (thus determining the orientation(s) of the magnetometer (106) when the magnetic field measurements are / were determined); and b. numerically estimating (e.g., using the iterative process) the location of the magnetometer (106) in the three orthogonal dimensions (3D) using a combination of:i. the two or more magnetic field measurements; ii. the two or more respective source locations; iii. the mathematical model representing the dipole of the magnetic field source; and iv the one or more magnetometer ori entati on s

[0025] Although the magnetometer orientation is relevant in respect of each of the two or more sets of magnetic field measurements, for a substantially stationary marker apparatus (102), the magnetometer (106) has a substantially stationary / fixed orientation, in which case the one or more magnetometer orientations are substantially mutually equal, and thus might be measured / recorded only once while the stationary marker apparatus (102) is in that orientation, which may be before, during and / or after the magnetic field measurements are actually recorded. Accordingly, the one or more respective magnetometer orientations may be only one magnetometer orientation for the measurements and / or mission.

[0026] The mathematical model associates the magnetic field measurements, the determined locations in 3D, and the 3D locations of the magnetic dipole provided by the magnetic field source (105). The mathematical model may optionally assume that the medium (104) is homogeneous, and / or that the medium (104) has a skin depth substantially approaching infinity for frequencies at which the magnetic field (b) is modulated.

[0027] The process (300) may include: a. receiving / determining (and / or measuring / recording) two or more respective orientations of the magnetic field source (105) at the two or more source locations in three orthogonal dimensions (3D orientation) (thus determining the orientations of the magnetic field source (105) when the magnetic field measurements are / were determined); andb. numerically estimating (e.g., using an iterative process) the location of the magnetometer (106) in the three orthogonal dimensions (3D) using a combination of: i. the two or more magnetic field measurements; ii . the two or more respective source locations; iii. the mathematical model representing the dipole of the magnetic field source; and iv. the two or more respective magnetic field source orientations.

[0028] The determining of the two or more orientations of the magnetic field source may include: a. determining (e g., measuring) one or more orientations of the mobile platform (108); b. determining (e g., measuring) one or more relative orientations of the magnetic field source (105) to the mobile platform (108); and c. estimating the two or more orientations of the magnetic field source (105) based on numerical addition / subtraction of the orientations of the mobile platform (108) and the relative orientations.

[0029] The determining of the two or more source locations may include: receiving / determining respective magnetic-field-measurement times when the magnetic field measurements are / were measured (e.g. recorded by the marker apparatus (102) as the magnetic field (b) measurements are made); and determining the respective locations of the magnetic field source (105) at the magnetic-field-measurement times from location tracking data representing the location of the or each magnetic field source (105) over time Determining the source locations based on the recorded times may be more accurate / efficient if the magnetic-field-measurement times can be recorded accurately and stored efficiently, e.g., on a data acquisition component that is separate / remote from the marker apparatus (102)("mobile DAQ (121)") and / or on a data acquisition component that is separate / remote from the marker apparatus (102) and in / on a stationary platform (126) ("stationary DAQ"), and if the location tracking data representing the source locations of the magnetic field source (105) over time can be recorded accurately and efficiently, e.g., using the navigation module (118) moving with the magnetic field source (e.g., on the drone), and / or using a remote location tracking system that tracks the path / location of the magnetic field source (105) with respect to time.

[0030] The magnetometer (106) may be in the form of a "total field magnetometer" and may be configured to measure a total scalar value of the magnetic field (b) (which may be referred to as a "total field") at the marker location, regardless of its direction.

[0031] The magnetometer (106) may be in the form of a "vector magnetometer" and may be configured to measure a value of the magnetic field (b) in each of one to three orthogonal dimensions (ID, 2D or 3D), and the two or more magnetic field measurements may therefore be non-coherent vector magnetic field measurements.

[0032] The magnetometer (106) may be in the form of a "coherent vector magnetometer" and may be configured to measure a phasor value of the magnetic field (b) in each of one to three orthogonal dimensions (ID, 2D or 3D), and the two or more magnetic field measurements may therefore be phasor magnetic field measurements. The measuring of the phasor value of the magnetic field may be referred to as "coherent detection" of the magnetic field (b).

[0033] The measurements of the magnetic field may include scalar magnetic field strength values (total field), vector magnetic field strength values (ID, 2D or 3D absolute values), and / or phasor magnetic field strength values (ID, 2D or 3D coherent values).

[0034] The determining of the two or more source locations may include: a. determining (e.g., measuring) locations of the mobile platform (108); b. determining (e g., measuring) a relative location of the magnetic field source (105) to the mobile platform (108); andc. estimating the two or more measurement locations based on numerical addition / subtraction of the locations of the mobile platform (108) and the relative location.

[0035] The determining of the measurements of the magnetic field (b) may include the magnetometer (106) detecting magnetic-induction (MT) signals / through-the-earth (TTE) signals from the magnetic field source.

[0036] The 3D locations may include three Cartesian values or three spherical values.

[0037] The mathematical model may include: a. a closed-form mathematical model with a system of closed-form equations (mathematical relationships); or b. a numerical integration model (e.g., a finite element analysis (FEA) model).

[0038] The closed-form equations represent solutions to Maxwell's equations for an (infinitesimal) magnetic dipole in a conducting / permeable medium with a simple structure. The numerical integration model represents integration of Maxwell's equations for an magnetic dipole in a conducting / permeable medium with any structure. The model may use a magnetic dipole modelled as an infinitesimal magnetic dipole (where the distance to the magnetometer (106) is far larger than the size of the magnetic field source (105)); alternatively, the magnetic field source (105) could be modelled as a loop / coil of finite extent, in which case the 'strength' of the magnetic field source (105) would be described by the current, turn shape and area and number of turns rather than by the "dipole moment". In some applications, the closed-form mathematical model may be preferable for being faster. In other applications, the FEA model may be preferable for being more accurate. For embodiments using the FEA model, the cost function includes: {modelled value} minus {measured value}, where each {value} can be total field, coherent vector or magnitude vector.

[0039] The localization process includes the data processing unit(s) / microprocessor} s) (110) (hereafter microprocessor (110) for purpose of brevity and simplicity) receiving the one ormore orientations of the magnetic field source (105) from the mobile platform (108) or location tracking system. The localization process may include the microprocessor (110) receiving: the selected / determined strength of the moment (m) of the magnetic field source(105) from the calibration process (302); and / or the selected / determined sensitivity (K) of the magnetometer (106) from the corresponding calibration process (303). The localization process includes the microprocessor (110) receiving the two or more magnetic field measurements from the magnetometer (106). The localization process includes the microprocessor (110) receiving the two or more source locations from a tracking module (e.g., a navigation module (118) attached to the mobile platform (108), and / or a remote location tracking system). The localization process includes the microprocessor (1 10) receiving the two or more orientations of the magnetic field source (105) from a relative pose measurement system and / or the tracking module. The process (300) thus includes: at least one microprocessor (110) receiving the one or more orientations of the magnetometer (106) in the marker apparatus (102); the microprocessor (110) receiving the selected strength of the moment (m) of the magnetic field source from the calibration process (302); the microprocessor (110) receiving the selected / determined sensitivity (K) of the magnetometer(106) from the corresponding calibration process (303); the microprocessor (110) receiving the two or more magnetic field measurements from the magnetometer (106), the microprocessor (1 10) receiving the two or more source locations from a navigation module or remote tracking system; and / or the microprocessor (110) receiving the two or more orientations of the magnetic field source (105) from a relative pose measurement system and / or a navigation module. In particular, the process (300) includes: at least one microprocessor (110) receiving the two or more magnetic field measurements; and the microprocessor receiving the two or more respective source locations.

[0040] The process (300) may include making the plurality of magnetic field measurements with respective SNRs or magnetic field strengths (which include mutually different SNR or magnetic field strength values), and only selecting ones of the magnetic field measurements (also referred to as selecting the "stations") having SNRs or magnetic field strengths over a selected threshold for the numerically estimating of the magnetometer location.

[0041] The process (300) may include localizing at least a portion of a drill bit or drill string by localizing a corresponding marker apparatus (102) during drilling with the drill bit or drill string, or after detachment of the portion from the drill bit or drill string.

[0042] The process (300) may include localizing a blast initiation device or a blast primer device for initiating blasts in commercial blasting operations based on the localization of at least one marker apparatus (102) that is attached to or includes or forms the blast initiation device or the blast primer device.

[0043] The process (300) may include localizing an explosive material in the opaque medium (104) by localizing at least one marker apparatus (102) buried in a selected location in the opaque medium (104) relative to and / or adjacent to and / or above the explosive material, optionally while digging / excavating a portion of the opaque medium (104) or after the digging / excavating.

[0044] The process (300) may include localizing seismic receivers (902) and / or seismic sources (904) by localizing the marker apparatuses (102) respectively incorporated in or attached to the seismic receivers (902) and / or the seismic sources (904).

[0045] The process (300) may include monitoring movement of broken rock (e g., in a heap) by repeatedly localizing the marker apparatus (102) placed on or buried in the broken rock.

[0046] The process (300) may include tracking an ore body during blasting, excavation and / or processing by the localization of the corresponding marker apparatuses (102), optionally including measuring draw of a stockpile by repeated localization of the corresponding marker apparatuses (102) over a selected time period.

[0047] The process (300) may include a wireless MI receiver component (117) on the mobile platform (108) gathering wireless encoded / modulated data signals from devices, in / on the opaque medium (104), incorporating the marker apparatuses (102), and / or capturing optical / thermal images, while on a path generating the magnetic fields (b).

[0048] The process (300) may include localizing a linear utility (e.g., a pipeline / powerline) in the opaque medium (104) by localizing at least one marker apparatus (102) buried in aselected location in the opaque medium (104) relative to and / or adjacent to and / or above the linear utility, optionally while digging / excavating a portion of the opaque medium (104) above the linear utility

[0049] The process (300) may include localizing measured physical parameters of the opaque medium (104) (e g., pressure, moisture, and / or temperature) by localizing at least one marker apparatus (102) buried in the opaque medium (104) with respective environmental sensors in / on the marker apparatus (102) to measure the physical parameter values, optionally while ploughing the opaque medium (104) adjacent / around the buried marker apparatus (102).

[0050] The process (300) may include localizing a person or a piece of equipment buried in the opaque medium (104), e g , an avalanche, a landslide, or a (collapsed) structure, by localizing at least one marker apparatus (102) attached to the person or the piece of equipment in the opaque medium (104)

[0051] The process (300) may include placing / burying the at least one marker apparatus (102) on / in the opaque medium (104) (rock, earth, foundations or structures), and the process (300) may include localizing the marker apparatus (102) repeatedly over a selected time period to monitor movement of the opaque medium (104).

[0052] Disclosed herein is a system (100) for remote localization of an object, the system (100) including: a. at least one magnetometer (106) configured for determining (e g., measuring) two or more measurements ("magnetic field measurements") of two or more respective magnetic fields (b) when the magnetic fields (b) are generated by at least one magnetic field source (105) that is remote from the or each magnetometer (106), wherein the or each magnetometer (106) is in an opaque medium (104) such that the magnetic field (b) extends through the opaque medium (104) and / or through a navigable medium (112) between the magnetic field source (105) and the or each magnetometer (106);b. a tracking module (e.g., a navigation module (118) attached to a mobile platform (108), and / or a remote location tracking system) configured for determining (including measuring / recording) two or more respective locations ("source locations") of the magnetic field source (105) in three orthogonal dimensions (3D) when the magnetic field measurements are / were determined (wherein the source locations may be in the opaque medium (104) or outside the opaque medium (104)); and i. at least one microprocessor (110) configured for numerically estimating a location ("measurement location") of the or each magnetometer (106) in three orthogonal dimensions (3D) using: ii. the two or more magnetic field measurements; iii the two or more respective source locations; and iv. a mathematical model representing a magnetic dipole of the magnetic field source.

[0053] The magnetic field source (105) may include at least one mobile magnetic field source attached to at least one mobile platform (108), optionally wherein the or each magnetic field source (105) includes a plurality of mobile magnetic field sources attached to the or each mobile platform (108), optionally wherein the or each magnetic field source (105) includes two or more mobile magnetic field sources attached two or more mobile platforms (108), optionally including one mobile magnetic field source attached to each mobile platform (108).

[0054] The tracking module may include a navigation module (118) attached to the mobile platform (108) and configured for measuring the 3D source locations of the magnetic field source (105).

[0055] The tracking module may include a remote location tracking system configured for recording the 3D source locations in a path of the mobile platform (108) during the measuring of the magnetic field measurements, and time stamping the 3D source locations.

[0056] The or each magnetic field source (105) may include at least one stationary magnetic field source attached to a fixed point, or stationary at a fixed point, in a reference frame of a site that includes the opaque medium (104) and the marker apparatus (102)

[0057] The microprocessor (110) may be configured for numerically estimating an orientation of the magnetometer (106), including in three orthogonal dimensions (3D orientation), and estimating an orientation of the marker apparatus (102) (on / in the medium (104)) from the numerically estimated orientation of the magnetometer (106).

[0058] The magnetic field source (105) may be configured to generate the magnetic fields (b) with a selected strength or moment, which may include a selected value and / or a selected range of values (which may be referred to as a "calibrated strength range"), and the microprocessor (110) may be configured for using the selected strength or moment with the mathematical model when numerically estimating the location of the magnetometer (106).

[0059] The marker apparatus (102) may be configured to measure / control the orientation of the magnetometer (106), and the microprocessor (110) may be configured for using the measured / controlled orientation of the magnetometer (106) with the mathematical model when numerically estimating the location of the magnetometer (106).

[0060] The system (100) may include a relative pose measurement system and / or a navigation module configured for determining (e.g., measuring) two or more orientations of the magnetic field source (105) at the two or more source locations in three orthogonal dimensions (3D orientation); and the microprocessor (110) may be configured for numerically estimating the location of the magnetometer (106) in the three orthogonal dimensions (3D) using a combination of: a. the two or more magnetic field measurements; b. the two or more respective source locations; c. the mathematical model representing the dipole of the magnetic field source; andd. the two or more magnetic field source (105) orientations.

[0061] The magnetometer (106) may include a total magnetometer configured to measure a total scalar value of the magnetic field (b) at the measurement location, regardless of its direction.

[0062] The magnetometer (106) may include vector magnetometer configured to measure a value of the magnetic field in each of one to three orthogonal dimensions (ID, 2D or 3D), and the two or more magnetic field measurements may be non-coherent vector magnetic field measurements.

[0063] The magnetometer (106) may include a coherent vector magnetometer configured to measure a phasor value of the magnetic field in each of one to three orthogonal dimensions (ID, 2D or 3D), and the two or more magnetic field measurements may therefore be phasor magnetic field measurements, including a recorded relative phase between the orthogonal components.

[0064] The magnetometer (106) may be configured to measure the magnetic fields (b) with a selected sensitivity (K), which may include a selected set of values and / or a selected range of values (which may be referred to as a "calibrated sensitivity range"), and the microprocessor (110) may be configured for using the selected sensitivity (K) with the mathematical model when numerically estimating the location of the magnetometer (106).

[0065] The system (100) may include at least one marker apparatus (102) substantially adjacent to, coupled to or incorporated into a drill bit or a drill string.

[0066] The system (100) may include at least one marker apparatus (102) that includes or forms a blast initiation device or blast primer device for initiating blasts in commercial blasting operations.

[0067] The system (100) may include at least one marker apparatus (102) buried in a selected location in the opaque medium (104) relative to and / or adjacent to and / or above explosive material.

[0068] The system (100) may include at least one marker apparatus (102) incorporated respectively into the seismic receivers (902) (hydrophones / geophones) and / or the seismic sources (904) (blasting devices).

[0069] The system (100) may include at least one marker apparatus (102) buried in broken rock (e.g., in a heap).

[0070] The system (100) may include at least one marker apparatuses (102) buried adjacent to or in an ore body (e.g., down a borehole).

[0071] The mobile platform (108) may include the wireless MI receiver component (117) configured for receiving wireless encoded / modulated data signals from devices in / on the opaque medium (104). The mobile platform (108) may include at least one optical / thermal camera configured to capture images from the mobile platform (108) while the mobile platform (108) travels along a path and makes the magnetic field measurements

[0072] The system (100) may include at least one marker apparatus (102) buried in a selected location in the opaque medium (104) relative to and / or adjacent to and / or above a linear utility (e.g., a pipeline / powerline) in the opaque medium (104).

[0073] The marker apparatus (102) can include one or more environmental sensors configured to detect, monitor, estimate, or measure physical parameters of the surrounding portion of the opaque medium (104), and the environmental sensors may include temperature sensors and / or moisture sensor (e g., for soil monitoring).

[0074] The system (100) may include at least one marker apparatus (102) incorporated into a marker beacon for mountain workers or engineering workers, e.g., attached or incorporated in clothing, modified ski passes / access tags, and / or smartphone cases / power banks.

[0075] The system (100) may include an uplink channel from the marker apparatus (102) for transferring uplink information, including: the two or more magnetic field measurements (typically with respective times or other information representing the respective source locations); and optionally the one or more orientations of the magnetometer (106).

[0076] In one or more implementations, the marker apparatus (102) may include an accelerometer (818) and / or a magnetometer (820) configured to measure an orientation of the magnetometer (106) when stationery relative to Earth's gravity and / or the Earth's magnetic field (or "geomagnetic field").

[0077] Accordingly, disclosed herein is a marker apparatus (102) for localizing buried objects, the marker apparatus (102) including: a. an accelerometer (818) and / or a magnetometer (820) configured to measure an orientation of a magnetometer (106) of the marker apparatus (102) when stationery relative to Earth's gravity and / or the Earth's magnetic field (or "geomagnetic field"); and b. a marker wireless MI transmitter component (e.g., including a through-the- earth (TTE) or magnetic induction (MI) transmitter with a transmit antenna) in the marker apparatus (102) configured to transmit an uplink signal representing the uplink information (mentioned hereinbefore) through the medium (104) (in which the marker apparatus (102) is stationery, which may have a surface, e g., including earth / rock / ice / water) such that the measured magnetometer orientation can be used to estimate (including by calculation) a location of the marker apparatus (102) in three orthogonal dimensions (3D). The uplink information can be transmitted from the marker apparatus (102) via a wireless MI uplink signal to the wireless MI receiver component (117), which may be in or outside the medium (104), and / or via a wireless MI multihop signal (130) between a pair of the marker apparatuses (102), which may be in or outside the medium (104), as shown in FIG. 1.

[0078] Thus the marker apparatus (102) can communicate uplink information via the uplink signals (which may be in a different channel) such that the mathematical model is informed of the orientation in space reducing unconstrained variables when using the mathematical model.

[0079] In addition, disclosed herein is a marker apparatus (102) for localizing buried objects, the marker apparatus (102) including: a. an accelerometer (818) and / or a magnetometer (820) configured to measure an orientation of a magnetometer (106) of the marker apparatus (102) when stationery relative to Earth's gravity and / or the Earth's magnetic field; and b. a microcontroller (806) configured to control the magnetometer (106) in the marker apparatus (102) based on the measured orientation of the magnetometer (106) such that the magnetometer (106) measures a magnetic field (b) with a selected orientation (e.g., such that the measured magnetic field (b) is equivalent to that of coil with an axes controlled by the microcontroller (806)).BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Some embodiments of the present invention are hereinafter described with reference to the accompanying drawings in which: o FIG. 1 is a side-view schematic diagram of a system for localizing buried objects in which dashed lines represent wireless signals and lines of curves represent detectable magnetic fields; o FIG. 2 is a side-view schematic diagram of a mobile platform of the system including a knee; o FIG. 3 is a flow chart of an overall process performed by the system; o FIG. 4 is a flow chart of a path generation process of the overall process, o FIG. 5 is a flow chart of a data reduction process of the overall process; o FIG. 6 is a flow chart of an inversion process of the overall process; o FIG. 7 is a sketch of a marker apparatus of the system; o FIG. 8 is a block diagram of electronic components of the marker apparatus; o FIG. 9 is a side-view schematic diagram of the system configured for a partially underwater (or "transition zone") seismic blasting application;o FIG. 10 is a plan-view schematic diagram of a path of the mobile platform over a medium with a plurality of marker apparatuses; o FIG. 11 is a side-view schematic diagram of the system configured for an on-land seismic blasting application; and o FIG. 12 is a side-view schematic diagram of the system configured for an underwater (or "transition zone") seismic blasting application.DETAILED DESCRIPTION

[0081] Described herein are a system (100) and a process (300) for localizing objects, including for locating marker apparatuses (102) that are stationery (which includes being buried / submerged) with respect to, in, and / or seated / placed on, an opaque (non-transparent) medium (104) that can include a mixture of materials. This locating of the marker apparatuses (102) includes determining their locations in three orthogonal dimensions, thus determining "3D locations". This locating of the marker apparatuses (102) may be referred to as "remote localization", "remote marker localization" or "wireless marker localization" because the locations are measured / detected remotely, using generated magnetic fields (b) that penetrate through the medium (104), without needing to physically / electrically contact / touch the marker apparatuses (102); similarly, the marker apparatuses (102) may be referred to as "wireless markers" and / or "remote markers". The magnetic fields (b) are generated by at least one magnetic field source (105), e.g., a mobile magnetic field source on / in at least one mobile platform (108) that is mobile with respect to the one or more marker apparatuses (102) being localized. The magnetic fields (b) may be referred to as "localization fields".

[0082] The generated magnetic fields are vector fields denoted by the symbol "b" herein for consistency with the pseudocode in the Appendices, and illustrated by lines of curves in FIGs. 1, 1 1 and 12. The generated magnetic fields (b) can analogously be denoted by the symbol “B” or the symbol “H”, including in bold type, since a skilled addressee in the field of electromagnetics would understand that the magnetic field strength field (H), measured in ampere per meter, and the magnetic flux density field (B), measured in tesla, are closelyrelated vector fields, equal in direction and proportional in magnitude in a non-magnetic medium.

[0083] The system (100) and the process (300) may be referred to as providing "magnetic tracking / localization", "dipole tracking / localization" and / or "radiolocation" because the localization is based on using the generated magnetic fields (b). Thus, the generated magnetic fields (b), at least when they are detectable, may also be referred to as "localization signals". The system (100) and the process (300) may be referred to as providing "position tracking" or "position and orientation (P&O) tracking", e g., if a portion of the medium (104) containing the marker apparatus (102) moves, thereby carrying the marker apparatus (102). The system (100) and process (300) use the generated magnetic fields (b), which include or are quasi-static magnetic fields substantially in the near-field region or zone (or substantially in a transition region or zone between the near-field and the far-field) of the magnetic field source (105) and the stationery marker apparatuses (102) defined by wavelengths of the generated magnetic fields (b), and by skin depths of the medium (104) as described hereinafter. In mining / quarrying operations, the marker apparatuses (102) may be referred to as "ore markers" because they may be buried adjacent to or in an ore body, and the marker apparatuses (102) may be used for tracking ore during blasting, excavation and / or processing. In heap leaching operations, the marker apparatuses (102) may be referred to as "movement markers", "monitoring sensors", and "primers". In operations marking buried objects, including pipelines / powerlines or explosive initiators / primers, the marker apparatuses (102) may be referred to as "markers" or "leakage sensors" for pipelines; or, if the marker apparatuses (102) include the explosive initiators / primers as attachments or in a shared housing / shell / unit, the marker apparatuses (102) may be referred to as "marker components" or "radio modules". In operations tracking drills and drill-bit portions, the marker apparatuses (102) may be referred to as "drill trackers" or "attachments" or "components" of the drill bits or drill strings. In seismic exploration operations, the marker apparatuses (102) may be referred to as "attachments" or "components" of the seismic sources and / or seismic receivers. In soil monitoring operations, the marker apparatuses (102) may be referred to as "attachments" or "components" of the soil sensing devices. In emergency operations, the marker apparatuses (102) may be referred to as "trackers" or "beacons" worn by or attachedto a person or piece of equipment. In civil engineering and construction operations, the marker apparatuses (102) may be referred to as "markers", "trackers" or "beacons" worn by or attached to a person or piece of equipment, or attached to or embedded in the structure. In geological, seismological or construction monitoring, the marker apparatuses (102) may be referred to as "markers", "trackers" or "detectors" or "monitors" that are seated / placed on, attached to, or embedded in the rock, earth, foundations or structures to determine movement over time.System (100)

[0084] As shown in FIG. 1, the system (100) described herein includes: a. the at least one marker apparatus (102) configured to be buried / submerged and remain stationary relative to, in or on a portion of the opaque medium (104) (which can be an opaque or a non-transparent medium, including a mixture of materials) at the marker location, the marker apparatus (102) including at least one magnetometer (106) (also referred to as a "magnetic field sensor", "magnetic flux sensor" or "in-device magnetometer") configured to detect / measure the magnetic fields (b), which are modulated, such that the magnetometer (106) is configured to detect the magnetic fields (b), and to measure the magnetic fields (b) (transmitted through the opaque medium (104) and / or a navigable medium (112)) transmitted from each of two or more source locations (which may also be referred to herein as "stations" or "source stations", which are mutually and substantially different source locations relative to the marker location), thus generating at least one magnetic field value for each of the two or more source locations of the magnetic field source (105); b. the magnetic field source (105); c. the at least one mobile platform (108), e.g., a vehicle, configured to move / carry at a mobile magnetic field source between the source locations, including moving / carrying the mobile magnetic field source while it generatesthe magnetic field (b), thus allowing the magnetometer (106) to make the magnetic field measurements while the mobile magnetic field source is continuously moving (including keeping a speed of the at least one mobile magnetic field source substantially above zero meters per second) along a path; and d. at least one data processing unit or digital microprocessor (110) configured to estimate the marker location of each of the or each marker apparatus (102) in the three orthogonal dimensions (3D) based on: the measurements of the magnetic field (b) from the marker apparatus (102); the recorded source locations associated with these measurements; and at least one predefined mathematical model representing a magnetic dipole of the magnetic field source (the mathematical model including modelled magnetic field strengths from the model magnetic dipole at modelled source locations in 3 mutually orthogonal directions).

[0085] The system (100) and process (300) measure the magnetic fields (b) produced by the magnetic field source (105), and then infer the position of the marker apparatus (102) from the shape and strength of those magnetic fields (b) and the source positions of the magnetic field source (105) while those magnetic fields (b) are being generated. The system (100) is configured to determine the 3D position of each magnetic field measurement (based on the 3D position of the magnetic field source (105) when it is generating the magnetic field (b)) in a frame of reference, e g., in a global frame of reference. Thus the system (100) is configured to identify 3 orthogonal spatial values in the 3 mutually orthogonal directions (e g., in Cartesian coordinates or in spherical coordinates) for each magnetic field value.

[0086] The magnetometer (106) in the marker apparatus (102) may include a scalar magnetometer that measures a total / ab solute magnetic field value of the magnetic field (b) from each source location. The magnetometer (106) may include a non-coherent vector magnetometer or a coherent vector magnetometer (or "phasor magnetometer") that measures a directional / vector magnetic field value (in ID, 2D or 3D) at the marker location from each source location. With a vector magnetometer, the system (100) is configured to determinethe 3D position and 3D orientation of the magnetic field source (105) when each magnetic field measurement is made (based on the 3D position and orientation of the mobile platform (108)), in the frame of reference, and this is used to determine the 3D position of the magnetic field measurements: thus, in this configuration, the system (100) may identify a minimum of 6 values, including in the 3 mutually orthogonal directions and in 3 mutually orthogonal orientations (pitch, roll, yaw), for each source location. When configured to measure the value of the magnetic fields (b) in the three orthogonal dimensions (3D), the vector magnetometer may be referred to as including a "triaxial" magnetometer since it senses the magnetic fields (b) along three orthogonal axes. The coherent vector magnetometer ("phasor magnetometer") is a vector magnetometer that also measures / records phase differences between the two or more orthogonal components of the measured generated magnetic fields (b) (but not necessarily relative to the magnetic field source (105)), and these phase differences (also known as "phase reference information") are recorded (by a data acquisition (DAQ) component (114) on the marker apparatus (102), as shown in FIG. 1) between the different orthogonal axes for the magnetic field measurements from each source location: the phasor component is thus a reconstruction from a series of instantaneous samples of the magnetic fields (b), recorded by the DAQ component (114), e g , reconstructed via a frequency transformation process (e.g., based on a fast Fourier transform, or a Hilbert transform) or via complex sampling (using a mixer), into a phasor form — this reconstruction can be based on the time base of the recorded measurements of the magnetic fields (b) from each source location by matching the below ground-signal measurements to the above-ground vehicle position measurements, e.g., by time stamp or other representation / ID that mutually differentiates the source locations, e g., source-location-codes and / or sequence codes (also referred to as "location codes") that uniquely identify the source locations for the inversion process (340) in the modulation of the magnetic fields (b) and / or in downlink signals / a downlink channel at the same times that the magnetic fields (b) are respectively measured / sensed by the magnetometer (106), thus uniquely identifying the source location for each magnetic field measurement in data in the marker component (102), e g., recorded in the DAQ component (114) — various processes for matching the sourcesensor pairs are described hereinafter in the Data Reduction Process (500) and the Inversion Process (340).

[0087] The process (300) includes a localization process (338) that solves / applies the mathematical model to effectively determine / estimate three or more unknown values relating to the marker apparatus (102). Since the 3D location of the marker apparatus (102) is unknown, the mathematical model has at least three unknown values in the form of the 3D location. The orientation of the marker apparatus (102) may also be unknown or may be partially unknown (depending on use of an accelerometer (818) and / or a "compass" magnetometer (820) in the marker apparatus (102) described hereinafter), so the mathematical model may also have one or two further unknown values in the form of the magnetometer (106) orientation (if the magnetometer (106) is rotationally symmetric, e.g., a single axis coil, at least one orientation direction need not be determined). The magnitude of the magnetic moment (m) of the magnetic field source (105), and thus the strength of the magnetic field source (105), may also be unknown or known only to within a calibrated range (depending on use of a calibration process (302) described hereinafter), so the mathematical model may also have an additional unknown in the form of the magnetic dipole magnitude / strength. The sensitivity (K) of the magnetometer (106) may be unknown, or known only to within a calibrated range (depending on use of a calibration process (303) described hereinafter) to improve efficiency of the localization

[0088] As the process (300) uses the mathematical model for determining the measurement location, which is the location of the magnetometer (106) while it is measuring the magnetic fields (b) (also referred to as "localization" of the measurement location), the process (300) may be referred to as providing "model-based localization". As the process (300) determines the measurement location in 3D without requiring knowledge of previous locations of the marker, the process (300) can use the magnetic field measurements taken after a blasting operation, including wherein the marker apparatus (102) is in a post-blast muckpile The localization process (338) includes using a strength of the moment (m) of the magnetic field source (105) if available, e g., in calibration data from the calibration / calibrate process (302), and using the magnetometer sensitivity (K) if available, e.g., in calibration data from the calibration / calibrate process (303).

[0089] The system (100) and the process (300) require a minimum number of source locations (of the magnetic field source (105)) and corresponding measured magnetic fieldvalues (at the magnetometers (106) from those source locations), and this minimum depends on: the type of the magnetometer (106) — which can be scalar or vector or phasor, and whether other measurements / controls can reduce the number of the unknown values relating to the marker apparatus (102), e.g., by controlling or measuring the orientation of the magnetometer (106) and / or of the marker apparatus (102) and / or by calibrating the sensitivity of the magnetometer (106) and / or the strength of the magnetic field source (105). Using the mathematical model to estimate the 3D marker location when there are only 3 unknown values may be referred to as solving for 3 degrees of freedom (DoF); similarly, if there are 5 or 6 of the unknown values, it may be referred to as solving for 5 DoF or 6 DoF. In practice, the system (100) and the process (300) use substantially more measurements than the minimum number, including substantially 10, 100 or 1000 times more than the minimum number, including because the field measurements may have low signal-to-noise ratios (SNRs), and using the substantially more measurements can increase the accuracy of the marker location estimates. In an example, a 10 m by 10 m flight pattern may use substantially 100 field measurements (e.g., approximately 30 3D vector measurements, or 100 scalar measurements); in another example, a wider flight pattern over more space may use substantially 1000 field measurements.

[0090] The magnetic field (b) may be modulated, e.g., with at least one carrier frequency (fc) and wavelength, such that it is not merely a DC field but a quasi-static field. The magnetic field source (105) — which provides the magnetic dipole in the mathematical model — includes alternating current (AC) dipoles that provide a time varying signal or at least one time varying component (e.g., sinusoidal), varying in time according to the carrier frequency (fc), that is detectable by the magnetometer (106) at the carrier frequency (fc). The modulation of the magnetic field (b) may therefore be referred to as including "AC modulation". The carrier frequency (fc) is selected during construction of the marker apparatus (102) and the magnetic field source (105), or in an encoding process (304) or in a CHANNEL SELECT process (312) as described hereinafter. The carrier frequency (fc) may include one or two selected carrier frequencies (fc), or set of carrier frequencies within a defined range, e.g., within an available range for a channel as described hereinafter. The use of the carrier frequency (fc) by the system (100) allows the magnetometer (106) todetect / measure the magnetic field (b), including its strength and optionally direction and phase (depending on the type of magnetometer), using a demodulation process based on the carrier frequency (fc), and this demodulation process can provide a significant mitigation of magnetic noise in the recorded magnetic field measurements.

[0091] Tn a path generation process (306) described hereinafter, the source locations may be selected to be substantially within a near field and / or within one wavelength of the expected marker locations at the TTE frequencies along the path. In some applications, the system (100) is configured such that the magnetic field source (105) generates the magnetic field (b) within 3 meters (m), or within 8 meters (e.g., for mines with shallow flitches), or within 13 meters (e.g., for a higher bench / muckpile), or within 50 meters, or within 100 meters, from the marker apparatuses (102). The system (100) may be configured such that the magnetic field source (105) is within substantially 1 m of the boundary / surface of the medium (104), or more than 1 m distance from the boundary / surface, or within 1 m to 10 m of the boundary / surface, or between 10 m and 100 m of the boundary / surface, e.g., for the mobile platform (108) to reliably clear a muckpile in a blasting application. Different distances between the magnetic field source (105) and the magnetometer (106) may have different preferred inversion processes (described hereinafter) when numerically estimating the marker location using the mathematical model: e.g., when using the coherent vector magnetometer, at shorter distances there may be good recovery of the phase information, so a coherent vector inversion process may provide the most accurate fix, and at greater distances the signal level may be too low for accurate phase reconstruction, so a total field inversion process may be more accurate.

[0092] In the path generation process (306), the source locations forming the path are selected to be mutually spaced to provide a diversity of source locations, and at least a plurality of the source locations may be preferably not collinear or coplanar. In the path generation process (306), the source locations may be selected to be sufficiently close to the associated likely marker location such that they produce sufficient magnetic field strength to be within the magnetic field detection range of the magnetometer (106), while still being substantially mutually separated, e g., circumferentially around a likely location of the marker apparatus (102). The magnetic field detection range of the magnetometer (106) may bedefined by a minimum signal -to-noise ratio (SNR) of the (modulated) magnetic field (b) detected by the magnetometer (106). The path may have a square-function shape, e.g., as shown in FIG. 10, to cover all marker apparatuses (102) in the area under / above the path, or the path may have an irregular shape, e g., selected by a remote pilot controlling the mobile platform (108), such that the regions of interest are substantially covered. The path may be selected, either in advance or by the pilot / controller while moving, such that the region of space where the magnetic fields (b) are detectable (i.e., the SNR is above the minimum threshold described hereinafter) covers / encompasses the likely / expected marker locations.

[0093] The system (100) and process (300) can work without line-of-sight (LOS) between the magnetic field source (105) and the magnetometers (106) because the magnetic fields (b) can pass through the non-transparent / opaque medium (104) that substantially attenuates / blocks electric fields and electromagnetic waves, e.g., infrared signals, that could be practically provided by the mobile platform (108) and detected by the marker apparatuses (102), e.g., as the modulation wavelength of the magnetic field (b) is substantially greater, including orders of magnitude greater, than the dimensions / size of the marker apparatus (102) or the magnetic field source (105). Accordingly, the practical size of the magnetic field source (105) is generally much less than the length of the wavelength of the modulated magnetic fields (b), and the magnetic field source (105) can be approximated to be a source point in the processes described herein

[0094] As shown in FIG. 1, the system (100) can include a plurality of the marker apparatuses (102).

[0095] In use, the at least one marker apparatus (102) is arranged, placed, dropped, or embedded to be substantially stationery (e.g., on / buried / submerged) with respect to at least a portion of the non-transparent medium ("opaque medium (104)") The non-transparent medium (104) generally includes materials that substantially inhibit / block visible and radiofrequency radiation, including ore, rock, broken rock, stone, rubble, debris, gravel, cement, stemming material, soil, dirt, sand, clay, mud, sediment, snow, ice, hydrocarbon fuel reservoirs, civil infrastructure, building materials, construction materials, earth, coal, stockpiles of ore / waste, tailings, landfill, concrete (including in civil engineering structures,e.g., in dam walls), foliage and / or tree cover. The non-transparent medium (104) may include substantially fluid / liquid materials including water, e.g., for undersea applications.

[0096] As described hereinafter, the navigation module (118) can include a global navigation satellite system (GNSS) receiver and INS navigation system, and / or a Light Detection and Ranging Simultaneous Localization and Mapping (LiDAR SLAM) system, and / or a light detection altimetry and velocimetry (LiDAV system, e.g., from Advanced Navigation). The LiDAR SLAM system may be used by the mobile platform (108) to measure the position of its surroundings, navigate through them, and avoid collisions, thus generating position and orientation as described hereinafter, and may assist with flight underground and near bench / muck surface an high walls (where a pilot would not have good visual line of site), and the LiDAR SLAM can be georeferenced to GNSS when above ground. The LiDAV system may be used for vehicle pose measurement near / underground The remote location tracking system, which tracks the path of the vehicle (108) (and thus the magnetometer (106) with respect to time), may include two or more optical cameras, reflective laser targets or radar targets, or sonar systems for underwater vehicles.Magnetic Field Source (105)

[0097] As described hereinbefore, the magnetic field source (105) is configured and controlled to generate the magnetic fields (b), with the magnetic-field modulation, for detection by the magnetometer (106) and for corresponding demodulation and recording by the magnetometer (106) and the marker DAQ component (114). The magnetic-field modulation can include the AC modulation at the at least one carrier frequency (fc), and the corresponding demodulation — by the magnetometer (106) / DAQ component (114) — can thus include demodulating based on the at least one carrier frequency (fc). The AC modulation may include frequency -shift keying (FSK) using previously available FSK methods. The magnetic-field modulation can allow for more sensitive detection / measurement of the magnetic fields (b), e.g., by allowing rejection / filtering of noise sources based on the demodulation, e.g., rejection of low-frequency (DC) noise and / or high-frequency noise.

[0098] As shown in FIG. 1, the system (100) can include a wireless MI transmitter component (116) configured to transmit downlink signals to the markers (102). In some implementations, the wireless MI transmitter component (116) can include or use the magnetic field source (105), and the magnetic field source (105) can be configured and controlled to transmit the downlink signals by at least one signal modulation of the magnetic field (b) in addition to the magnetic-field modulation used by the magnetometer (106) for detection / measurement / recording of the strength and direction of the magnetic field (b). The at least one signal modulation can include frequency modulation, phase modulation and / or amplitude modulation, and the corresponding demodulation and recording by the magnetometer (106) / DAQ component (1 14) can thus include respective frequency demodulation, phase demodulation and / or amplitude demodulation using selected modulation and demodulation processes configured into the magnetometer (106) / DAQ component (1 14) and the marker apparatus (102) respectively. The downlink signals can provide an downlink channel (also referred to as a "DL comms channel") that is defined during the construction of the magnetic field source (105) and the marker apparatus (102), or in the encoding process (304) or in the CHANNEL SELECT process (312) as described hereinafter. By way of the downlink channel, the downlink signals can transmit information (referred to as "downlink information" generally represented by digital data) from the magnetic field source (105) to the magnetometer (106) that is additional to, and transmitted in parallel with, the magnetic field (b).

[0099] The magnetic field source (105) can be rotationally symmetrical about its magnetic axis, thus having only 2 orientational DoF.

[0100] The magnetic field source (105) can be modelled by a magnetic dipole with a single axis, or as two or three magnetic dipoles with respectively two or three axes.

[0101] The magnetic field source (105) may include an MI antenna that may be used for: a. the generation of the (modulated) magnetic fields (b); b. the transmission of the downlink signals; and / orc. receiving of uplink signals from the marker apparatus (102) together with a wireless MI receiver component (117) described hereinafter.

[0102] The MI antenna of the mobile magnetic field source may comprise a single-axis coil antenna or a multi-axis coil antenna (e g., for generating the magnetic fields (b) with selectable / controllable directions). Requiring only one magnetic source axis, and thus only one single-axis coil antenna, instead of two or three, decreases complexity of the physical layout in the magnetic field source (105), and may avoid the need to multiplex signals to multiple different axes, may avoid the cost of three coils compared to one, and / or may require less power than two or three coils.

[0103] Although, as mentioned hereinbefore, the MI antenna may be used for both transmission (of the downlink signals) and reception (of the uplink signals), the MI antenna may still be configured primarily for transmission rather than reception, e g., because the SNR of the magnetic field measurements needs to be higher for improved localization in some implementations. In other implementations, the Ml antenna may be used for both transmission (of the downlink signals) and reception (of the uplink signals), and may be configured primarily for reception rather than transmission if the uplink signals are weaker than the downlink signals, e.g., if more power and / or coil diameter is available on / in the mobile platform (108) (for the magnetic field source (105) and the wireless MI transmitter component (116)) than on / in the marker apparatus (102) (for a marker MI antenna in the marker apparatus (102)), and / or if there is lower noise at the marker location in the opaque medium, e g., underground, where the marker Ml antenna is located during the communication and the magnetic field measurements, compared to the source location (i.e., the location of the wireless MI receiver component (117), which may use the same antenna as the magnetic field source (105) and / or the wireless MI transmitter component (116)).

[0104] As shown in FIG. 1, the at least one magnetic field source (105) may include at least one mobile magnetic field source that operates in the navigable medium (112) that is separated from the opaque medium (104) by a boundary (which may include a surface of the opaque medium (104)). The system (100) may include a plurality of the mobile platforms (108), each with at least one mobile magnetic field source, forming a "swarm" of mobilemagnetic field sources operating mutually simultaneously to generate a plurality of downlink magnetic fields (b). The navigable medium (112) may be space, air or water: e.g., a portion of the Earth's atmosphere, air above an open mine, air in an underground mine, air above a body of water, water adjacent a glacier, or water adjacent a sea bed. The navigable medium (112) may be the same medium / fluid as the opaque medium (104), e g., water. The generated magnetic fields (b) and downlink signals penetrate through the navigable medium (112) to reach the magnetometer (106), e.g., as shown in FIG. 1.Marker Apparatuses (102)

[0105] The magnetometer (106) can include at least one marker MI antenna for detecting / measuring / transducing the magnetic field (b) and the associated MI downlink signals from the magnetic field source (105).

[0106] The marker Ml antenna can include a single-axis marker MI antenna, with a single axis, that is rotationally symmetrical about its magnetic axis, with only 2 orientational DoF.101071 As shown in FIG. 7, the marker Ml antenna may include a coil (702). The coil (702) including many turns of an electrically conductive material (e.g., copper or aluminium wire) with an electrically insulating coating (e.g., a plastic material or enamel material). The coil turns carry a detected electric current, representing the received modulated magnetic field (b), formed by induction. To generate the uplink signals, an electric driving current is generated in the coil turns a coil driver circuit (804). The coil (702) is configured for magnetic field detection, MI reception and MI transmission by: having a coil diameter that substantially equal to the diameter of the marker apparatus (102), e.g., as large as practically possible inside a shell (714) of the marker apparatus (102); and by drawing a maximum current from a power source (e.g., battery) of the marker apparatus (102) to provide the electric current in the coil (702).

[0108] The marker MI antenna may be used for both transmission (of the uplink signals) and reception (of the downlink signals), but the marker MI antenna may be configured primarily for transmission rather than reception if the downlink signals are easier to detect than theuplink signals, e.g., if more power and coil diameter is available for the magnetic field source (105) than for the marker MI antenna in the marker apparatus (102), and if there is lower noise at the marker location in the opaque medium, e.g., underground, where the marker MI antenna is located, than at the source location where the magnetic field source (105), the wireless Ml receiver component (117) and the wireless MI transmitter component (116) are located (each with a shared or respective MI antenna).

[0109] As shown in FIG. 7, the marker Ml antenna may include a bobbin (704) onto which the coil (702) is mounted for mechanical stability. The bobbin (704) includes a low / non- conductive, low / non-permeable material, e.g., a plastic material. The construction of the coil (702) and bobbin (704) may include winding the turns of the insulated conductive material around the bobbin (704). The bobbin (704) may be filled with a magnetically permeable core (712), e.g., a magnetically permeable material, e.g., a ferrite or ferrite mixture or magnetic field permeable composite as described in International Patent Publication No.W02024076309 ("Electronic device”, Nielsen, Rasmussen and Zank, to Orica International Pte Ltd). The bobbin (704) may itself have the properties of the magnetically permeable core (712), or the mechanical function of the bobbin (704) — holding the coil (702) — may be provided by solid material of the magnetically permeable core (712), such that no separate bobbin part is required.

[0110] The marker apparatus (102) includes at least one printed circuit board assembly (PCBA) (708) with electronic components (800) of the marker apparatus (102).[oni] The power source is configured to power the other electronic components (800), including the marker MI antenna by way of the electric driving current. The power source may include a battery (706), e.g., as shown in FIG. 7. For some applications, the battery (706) may include a replaceable battery that fits removably into a battery holder (710) of the marker apparatus (102), e.g., if the marker apparatus (102) is configured to be re-used.

[0112] As shown in FIG. 8, the electronic components (800) in the marker apparatus (102) may include:a. the power source (802), including the battery (706) and a voltage regulator circuit (803) that regulates the voltage from the battery (706); b. a coil driver circuit (804) powered by the power source (802); c. at least one microcontroller (806), powered by the power source (802), connected or connectable to a programming input (814) that allows the microcontroller (806) to be configured to control the marker apparatus (102) to operate as described herein; d. a magnetic field feedback circuit configured to maintain stability of an uplink magnetic field (for the uplink signals) during substantially 100% of any uplink transmission time from the marker apparatus (102): the magnetic field feedback circuit may be in the form of a current sense circuit (808) configured to sense a current from the coil driver (804) and to generate a signal representing the current from the coil driver (804), wherein the current sense circuit (808) is electrically connected to the coil driver (804) and to the microcontroller (806) to transmit the value of the current to the microcontroller (806) — alternatively, the magnetic field feedback circuit may include a feedback magnetic sensor that measures the generated magnetic field strength from the antenna (in the form of the coil 702) and transmits a signal representing fluctuations in the generated magnetic field strength to the microcontroller (806) to stabilise the current to the marker antenna in the form of a negative feedback loop; e. a transmit / receive component (810), driven by the coil driver (804) when the marker apparatus (102) is transmitting, and connected to the marker Ml antenna, and configured to control the marker MI antenna to be in either a transmit mode (to transmit the uplink signals) or a receive mode (to receive the downlink signals and to measure the magnetic fields (b));f. a downlink MI receiver (812) configured to receive the downlink signals from the marker MI antenna via the Tx / Rx component (810) when in the receive mode for communications; and g. the magnetometer (106) of the different possible types described hereinbefore, which can be the same coil as used for the uplink and downlink communications.10113] The coil driver circuit (804), the magnetic field feedback circuit, the transmit / receive component (810), and the coil (702) can form the marker wireless MI transmitter component for sending the uplink signals.

[0114] The power source (802) provides sufficient voltage and current to power the other electronic components (800), e.g., substantially 3 to 21 volts (V), or at least substantially 0.5 V and / or no more than substantially 100 V. The programming input (814) may include an electrical connector (e g., a plug) or a wireless interface (e g., an infrared or near-field communication (NFC) interface that is configured to provide communication between the microcontroller (806) and the blast encoder (or equivalent device in non-blasting operations).

[0115] The coil (702) may have an average diameter of between 0.01 m and 0.3 m, which can correspond to a diameter of a borehole. The marker MI antenna can be driven at substantially or approximately 3 watts (W) or 6 W.

[0116] In some implementations, the marker apparatus (102) may include a mechanical self- righting mechanism in the form of a weighted gimbal that naturally aligns the marker antenna and magnetometer to a preselected orientation (e g., vertically) due to the force of gravity while the marker apparatus (102) remains stationary. In these implementations, the marker apparatus (102) includes an inner shell (with a weight at one end) that is free to rotate in at least 2 orthogonal directions in an outer shell such that the magnetometer (106) settles into preselected orientation (due to placement of the weight), e.g., a vertical orientation, by the force of gravity. However, as described hereinbefore, such mechanical self-righting marker apparatuses may be undesirable in some applications, e g., for being complicated to manufacture and / or prone to damage.

[0117] As shown in FIG. 8, the marker apparatus (102) may include the accelerometer (818) — also referred to herein as the "IMU" accelerometer (818), and optionally the magnetometer (820) — also referred to herein as the "compass" DC magnetometer (820), and these are configured to measure the orientation of the marker apparatus (102), which is stationery, relative to Earth's gravity and / or the Earth's magnetic field (or "geomagnetic field"). By measuring the gravity vector, the marker apparatus (102) detects the component of the measured magnetic fields (b) in the direction of gravity, and the associated "compass" DC magnetometer (820) in the marker apparatus (102) generates complementary information by detecting the direction of the Earth's magnetic field. By detecting both gravity and the Earth's magnetic field together, the accelerometer / magnetometer (818,820) provide complete orientation information (as long as they are not in the same direction, which would be unusual). The "compass" DC magnetometer (820) is configured to detect / measure the geomagnetic (DC) signal in contrast to the marker magnetometer (106), which is configured to detect / measure the modulated magnetic fields (b) and the downlink (AC) signals, e.g., by way of selection / control of a resonant frequency in the marker MI antenna (to match the carrier frequency (fc) of the modulated magnetic fields (b)) and / or filters in the magnetometer (106) / marker DAQ (114).

[0118] The accelerometer (818) and the DC magnetometer (820) are connected to the microcontroller (806) to provide the orientation measurements of the AC magnetometer (106) to the microcontroller (806). The microcontroller (806) is configured to use these marker orientation measurements: a. in an uplink process (324), to transmit the marker orientation measurements to the microprocessor (110), via the uplink information, to allow the use of the magnetometer orientation measurements in the numerically estimating of the marker location using the mathematical model, which reduces the number of unknown values in the mathematical model

[0119] In the uplink process (324), just sending the orientation from the accelerometer (818) without using the "compass" DC magnetometer (820) reduces the unknowns in the mathematical model, so can improve the processing efficiency / accuracy, but the processingefficiency / accuracy can be further improved by also sending the orientation from the "compass" DC magnetometer (820). Using just the accelerometer orientation eliminates one degree of freedom ("elevation" angle known), which may be beneficial, and using both the accelerometer and "compass" orientation eliminates two degrees of freedom ("heading" and "elevation" angles known), which may be more beneficial. If the magnetic axis of the marker magnetometer (106) is controlled to be vertical, using just the accelerometer orientation eliminates two degrees of freedom, so the compass orientation measurement may not be needed; however, if the magnetic axis of the marker magnetometer (106) is other than vertical, the accelerometer orientation eliminates only one degree of freedom, and the "compass" orientation is required to eliminate two degrees of freedom

[0120] The localization process (338) includes receiving the one or more orientations of the marker magnetometer (106) from the uplink process (324), thus the marker orientation information is transmitted to the surface and forms part of the localization calculation.

[0121] The accelerometer (818) and the "compass" DC magnetometer (820) could be mounted in the marker assembly (102) by the addition of at least one MEMS integrated circuit to the PCBA (708), e.g., near the microcontroller (806) and connected thereto, and to the electronic components (800). One integrated circuit may include the accelerometer 818 and the "compass" DC magnetometer (820), or there may be an integrated circuit for each.

[0122] Each marker apparatus (102) may be configured or configurable to store / include its unique ID (which is at least a quasi-unique ID), e.g., in the memory of the marker apparatus (102), e.g., in the microcontroller (806) and / or a separate memory storage (822) in communication with the microcontroller (806). The ID can be stored / written / hardcoded / configured into the marker (102) on manufacture, and / or stored / written / soft-coded by the blast encoder during the encode markers process (304), and / or in the downlink commands described hereinafter in the downlink processes (310). The marker apparatus (102) may be configured to transmit its stored ID in the uplink signals by the modulation thereof, including in the uplink information. The magnetometer (106) and / or the DAQ (114) may be configured to demodulate / decode the downlink signals — or at least received electronic signals representing the downlink signals. The microprocessor (110)may include or access a database or list of the IDs of the marker apparatuses (102) in the system (100) that the microprocessor (110) then associates with the estimated marker locations after estimating the marker locations. By having these IDs for the marker apparatuses (102) in the system (100), the microprocessor (110) can indicate which marker apparatuses (102) in the system (100) have been localized, and can thus determine and indicate if any marker apparatuses (102) in the system (100) have not yet been localized / detected (these are "missing markers"), which may allow the platform (108) to be directed to move along another pattern, e.g., close to expected locations for the missing markers, in an attempt to detect and localize additional IDs.

[0123] The marker apparatus (102) can be configured for deployment in a confined space proximate to or in the portion of the physical media. The marker apparatus (102) can have a geometry (including shape and size) configured for deployment in the confined space The confined space can be a borehole, and the geometry can include: a perpendicular width (e.g., diameter for a circular cross section) that is less that a borehole diameter (open diameter of the borehole); and a (longitudinal) length that can be limited by (i) loading manner and optionally (ii) other borehole contents. The coil (702) is configured based on the size of the marker apparatus (102). The marker apparatus (102) has an electrical power storage capacity associated with the size: for example, the marker apparatus (102) can be sized to fit into conventional boreholes, e.g., having an average diameter of substantially 4 to 6 cm (for a smaller embodiment) or substantially 10 to 20 cm (for a larger embodiment), and the battery (706) can be substantially equivalent to two or four commercially available "AA" size batteries (each of which can have substantially 1000 to 4000 milliampere hours capacity, e.g., substantially 3500 mAh for a lithium AA battery).

[0124] In some implementations, the marker apparatus (102) may include components that provide functionality apart from the localization, or can be attached to or incorporated in devices that provide functionality apart from the localization The marker apparatus (102) may include or form a blast initiator (which can be referred to as a blast initiation device), and / or a blast primer device, for initiating blasts in commercial blasting operations. The blast initiator / primer gives rise to an explosion or detonation. The marker apparatus (102) forming the blast initiator can be positioned in boreholes or blastholes. The downlink commands mayinclude initiation-specific MI signals, and representing enabling / disabling, encoding, querying, (re)programming, (re) synchronizing, and / or controlling operation and / or firing of selected ones of the blast initiators (as part of enabling / disabling, encoding, querying, (re)programming, (re)synchronizing, and / or controlling the operation and / or firing of blast initiators in association with a commercial blasting operation). The marker apparatus (102) can be integrated into an initiation device such that the marker and the initiation device are both within the shell (714). Alternatively, two or more of the marker apparatuses (102) may be configured to reside in two or more blastholes with initiation devices for commercial blasting operations, and / or in auxiliary boreholes located proximate to and separate from the blasthole in which the initiation devices reside. The marker apparatuses (102) can be coupled or attached to the initiation devices. The marker apparatuses (102) and the initiation device, when coupled or attached or integrated, can be configured, during manufacture, to utilize mutually different MI communication channels (including different signal frequency bands or frequencies or multiplexing channel) to mitigate the risk of the modulated magnetic field (b), or the uplink signals or the downlinks signals, causing initiation of the associated initiation device. The marker apparatus (102) can include the one or more sensors (including chemical / physical sensors, referred to herein as "environmental sensors") that detect, monitor, estimate, or measure physical parameters associated with the medium portion which they are deployed. The sensors can include a set of sensors configured for sensing selected environmental conditions or parameters, including temperature, moisture, pressure, and / or shock (e.g., for soil monitoring). The marker apparatus (102) can be fixed / attached to a drill bit or drill string configured to underground / rock drilling, e g., to drill boreholes. The marker apparatus (102) can include or be fixed / attached to seismic initiators / primers and / or hydrophones / geophones (or seismic sources and / or seismic receivers).

[0125] As shown in FIG. 1, the system (100) includes the data acquisition (DAQ) component (1 14) in / on each marker apparatus (102) that is configured to: record the magnetic field measurements of the magnetometer (106) from each source location, e.g., continuously / repeatedly over time for the duration of the measurements, record the magnetic field measurements (and respective orientations / accelerations if required by the mathematical model). Thus the DAQ component (114) records the outputs of the magnetometer (106) andthe respective times thereof, and optionally the respective accelerometer orientations and "compass" orientations described hereinafter, and optionally other uplink information.

[0126] The uplink information, transmitted from the marker (102) / marker DAQ component (114), via the marker's coil driver circuit (804) to the wireless MI receiver component (117), and / or optionally via the wireless MT multihop signal (130) in the uplink process (324) — which may include a multihop communications process, e.g., as described in Singapore Patent Application No. 10202301716Y, entitled "Signalling / communication system and method for devices" (OMS 3101), including a stationary platform (126) (or "ground multihop relay") as shown in FIG. 1, may include: a. a unique ID of the marker apparatus (102); b. measured orientation of the magnetometer (106) from a control / measure magnetometer orientation process (322) described hereinafter; and / or c. measurements from one or more environmental sensors (described hereinafter) that detect, monitor, estimate, or measure physical parameters associated with the medium portion which the marker apparatus (102) is deployed; and / or d. measurements / parameters pertaining to the state of the marker apparatus (102).

[0127] The measurements from the environmental sensors, the measurements / parameters pertaining to the state of the marker apparatus (102), and / or the source phase information may be referred to as "arbitrary data" because the values are not known in advance by the microprocessor (110). In contrast, the unique ID of the marker apparatus (102) could be known to the microprocessor (110) because it can be one of a selected set of IDs stored / accessed, e.g., in the microprocessor (110). The uplink information can therefore be referred to as including "arbitrary data", which is data that is not known to the microprocessor (110) or the wireless MI transmitter component (116), so the arbitrary data must be decoded / demodulated rather than just correlated for: the system (100) cannot rely just oncorrelation for the arbitrary data, but uses decoding / demodulation, which may require a relatively higher level of SNR.At Least One Magnetometer (106)

[0128] The at least one magnetometer (106) in the marker apparatus (102) may include a plurality of magnetometers, each configured and operating as the magnetometer (106) described herein.

[0129] The or each magnetometer (106) is configured to measure the strength of the magnetic field in which it lies. By measuring the strengths (and optionally directions and phases, depending on the type of the magnetometer (106)) at the marker locations, the shapes of the magnetic fields (b) from each source location are effectively determined by the system (100), or at least the distance or direction from which each magnetic field (b) is coming can be measured / estimated for each source location (or "source station"). Each source-sensor pair, i.e., each pairing of one magnetic field source (105) at one location with one magnetometer (106), is synchronised in the sense that the measurements are made while one of the magnetic fields (b) is generated from the source location.

[0130] The or each magnetometer (106) includes at least one magnetic sensor element configured to measure the magnetic field (b) at the marker location, and the process of measurement may include measuring the following, depending on the type of the magnetometer (106): a. a scalar value of the field (which represents the amplitude (A) of the magnetic field signal, including at a selected modulation frequency); b. a vector value of the field (which represents the amplitude (A) in ID, 2D or 3D); and / or c. a phasor value of the field (which represents the amplitude (A) and the phase (9) in ID, 2D or 3D), wherein the phasor is a complex number representing asinusoidal function whose amplitude (A), angular frequency (co), and initial phase (0) are time-invariant.

[0131] As mentioned hereinbefore, the or each magnetometer (106) — in combination with the DAQ component (114) in the marker apparatus (102) — may include: a. the scalar magnetometer (which may be referred to as a "total field magnetometer") configured to measure the magnetic field strength without measuring orthogonal components of the magnetic field severally (see the Total Field Inversion Process hereinafter); b. a ID vector magnetometer (or a "single-axis sensor") configured to measure the magnetic field strength along a single axis that is optionally fixed relative to the orientation of the magnetometer, e.g., fixed vertically such that it naturally aligns with gravity to have a constant or "fixed" Z / vertical orientation (see the Absolute Value Inversion Process hereinafter); c. a 2D vector magnetometer; d. a 3D vector magnetometer — a vector magnetometer with a three-axis sensor configured to measure the magnetic field strength along three mutually orthogonal axes at each measurement location (thus measuring three orthogonal components of the magnetic field ); e. a ID coherent vector magnetometer (see the Coherent Vector Inversion Process hereinafter), f. a 2D coherent vector magnetometer; and / or g. a 3D coherent vector magnetometer.

[0132] The scalar magnetometer may include a total field magnetometer, e g., a proton magnetometer or a caesium magnetometer.

[0133] The ID, 2D, or 3D vector magnetometers may include a flux gate or an induction coil (or "pick-up coil") for each axis.

[0134] The magnetometer (106) can be a 3-axis vector magnetometer configured for detecting magnetic flux in 3 mutually orthogonal axes. Alternatively, the magnetometer (106) can be a single axis magnetometer configured for detecting magnetic flux in 1 axis The magnetometer (106) can include a coil or loop antenna (referred to as a "receive loop") with an average diameter of between 0.01 m and 2 m; and the smaller loops may be coils on a ferrite core.

[0135] The 3D vector magnetometer may include three mutually orthogonal pick-up coils arranged to measure the three orthogonal components of the magnetic field separately. The ID, 2D, or 3D phasor magnetometers are configured to measure a magnitude and a phase of each orthogonal component of the alternating magnetic field / flux density of the modulated magnetic field (b), thus measuring a magnitude and a direction (thus a vector in ID, 2D or 3D) of the alternating magnetic field / flux density of the modulated magnetic field (b). The coherent vector magnetometer may be configured to measure the phase of each component by taking many measurements of the time-varying signal, from which the phase is determined / reconstructed. The coherent vector magnetometer is configured, by construction and calibration (including the calibration process (303)), such that any discrepancies in the phase delay on each axis are accounted for.

[0136] For the 3D magnetometers, the system (100) can measure all three components (x, y, z) of the magnetic fields (b)

[0137] As shown in FIG. 3, for the vector magnetometers and coherent vector magnetometers, the system (100) controls and / or measures the orientation of the magnetic field source (105) at each source location so the source locations are recorded (in a record mobile source position process (334)) at the same time as the orientation of each dimension of the magnetic field source (105) is recorded (in a record mobile source orientation process (336)) and this is at the same time as a record measured magnetic field (b) process (332) in the markers (102). The orientation of the magnetic field source (105) at each source location is recorded and used in the localization calculations described herein.

[0138] Determining the orientation of the or each magnetic field source (105) at each source location in the record mobile source orientation process (336) can allow for: a. more measurements to improve the accuracy / speed of the use of the mathematical model (including inversion of a forward model as described hereinafter, including allowing for more sophisticated inversion algorithms by enabling algebraic manipulation of the forward model); and / or b. correction of orientation changes of the magnetic field source (105), e.g., due to movement / wobble / orientation change of the magnetic field source (105) during operation.

[0139] Although the system (100) and process (300) described herein may be used if the marker (102) includes a self-righting mechanism, which potentially reduces the DoF of the marker in the mathematical model as described hereinafter, since the system (100) and process (300) do not require finding a signal maximum from the magnetic field source (105), nor a specific relative orientation between the magnetic field source (105) and the magnetometer (106), the marker apparatus (102) need not include a self-righting mechanism to keep its antenna in a predetermined orientation relative to gravity, and this allows each marker apparatus (102) to have a random / arbitrary orientation relative to the magnetic field source (105) / platform (108), which may be preferable in applications where the orientation of the marker apparatus (102) naturally changes (including partially randomly) due to movement of the medium (104), e.g., during dam wall movement or rock blasting. This allows for simpler marker construction, e g., not requiring a mechanical self-righting mechanism (e.g., an internal gimbal mechanism as in previous markers) that may be susceptible to damage / misalignment,. Not requiring a self-righting mechanism may allow the marker apparatus (102) to be constructed simply and inexpensively, which may be desirable for single-use markers, e.g., in blasting applications.

[0140] The system (100) and process (300) described herein may also allow for a simpler pattern of the source locations compared to previous systems using markers, e.g., a flight path for the mobile platform (108), because the source locations do not need to be coaxial with the marker apparatuses (102) as in previous systems — and the simpler pattern may allow forfaster location of multiple markers (102) at the same time, e.g., in experimental examples, up to 15 examples of the markers (102) have been located in a short flight. The simpler pattern may allow for a simpler (and less accurate) control system for the mobile platform (108): e g., the mobile platform (108) may be manually controlled in an imprecise pattern that does not need to follow a predefined pattern, so long as the magnetic field source (105) reaches within its magnetic field range of the plurality of markers (102) instead of requiring to travel over the tops of the markers, and instead of requiring to travel through the signal maxima as with previous (uplink) systems, e.g., mentioned in the background. The system (100) and process (300) described herein also allow for at least one fixed magnetic field source to generate at least some of the magnetic fields (b), from its fixed location, that are used in the 3D localization of the marker apparatus (102) because measurements from the plurality of source locations can be automatically integrated by the localization process and the fixed sources need not be vertically aligned with the marker apparatuses (102) as in previous systems. The system (100) and process (300) described herein allow for the or each mobile magnetic field source to be continuously moving while the marker magnetometers (106) are making the magnetic field measurements at the marker locations: the mobile magnetic field sources can be continuously moving, thus having a non-zero speed in a reference frame of a site that includes the at least one magnetic field source (105) and the marker apparatus (102) — e.g., a mine frame of reference, or a site frame of reference, or an environment frame of reference. The or each mobile magnetic field source is configured to generate the modulated magnetic fields (b) while its speed relative to the marker apparatuses (102) (on the ground, through the air, or through the water) is substantially non-zero (meters per second) while travelling along its path, where the marker (102) has sufficiently short accumulation time (or "integration time") for making the magnetic field measurements corresponding to each "station " / source location and a shorter accumulation time is selected for higher travel speeds. The accumulation time is controlled in the DAQ component (1 14) or in post processing in a separate (e.g., remote) computing system (described hereinafter), e g., the accumulation time can be substantially 0.5 seconds for a travel speed of up to substantially 3 or 4 m / s.

[0141] As mentioned hereinbefore, the at least one magnetic field source (105) may include the fixed magnetic field source, which has a fixed point as its position. The fixed point is anon-mobile point in a reference frame of the site that includes the at least one magnetic field source (105) and the marker apparatus (102), which may be a mine frame of reference, or a site frame of reference, or an environment frame of reference. Being "non-mobile" means a speed of the fixed point is zero in the reference frame. The fixed point may be a preselected 3D position, e.g., from being surveyed in, or a location determined after the magnetic field measurements have been made, e.g., from a schedule of fixed point identifiers and corresponding 3D locations. The fixed magnetic field source may be provided by a mobile magnetic field source that has been parked or located or attached to, or stationary at, the fixed point. In contrast to the mobile magnetic field source, the fixed magnetic field source does not need to measure its 3D orientation and 3D location for the system (100) to determine the source 3D orientation / location for each magnetic field measurement in the marker. For a fixed magnetic field source, the source locations can be recorded separately and associated with the magnetic field measurements separately, e.g., based on time, frequency and / or other identifier of the source location. The system (100) may include the fixed magnetic field source to enhance the results from the mobile magnetic field source. The fixed magnetic field sources need not be precisely located relative to the marker apparatuses (102) in advance because the system (100) and process (300) described herein do not require the marker (102) to be at a signal maximum or other predefined location relative to the source(s), unlike previous systems, e g., mentioned in the background The process of receiving / determining of the two or more magnetic field measurements may thus include using the or each fixed magnetic field source, which may mitigate the need to measure the location of the at least one fixed magnetic field source (105) while the magnetic field measurements are being made, e.g., because the location of the fixed point can be selected (e g., surveyed in) or measured before / after the magnetic field measurements are being made.

[0142] The system (100) and process (300) allow for the three-dimensional (3D) localization of the marker apparatus (102), thus combined horizontal and vertical localization at the same time and from the same set of measurements.Non-marker Data Acquisition Component (121) and Data Transmission Component (120)

[0143] As shown in FIG. 1, the system (100) also includes a data acquisition component that is separate / remote from the marker apparatus (102) as shown in FIG. 1 (referred to herein as a "mobile DAQ (121)"). The mobile DAQ (121) that is configured to: record each source location, e.g., continuously / repeatedly over time for the duration of the measurements, record the source locations (and respective orientations if required by the mathematical model) and optionally the record mobile source orientation process (336). These location and orientation measurements at each location may be referred to collectively as "pose measurements". Thus the mobile DAQ (121) records: the source locations and optionally the respective source orientations and optionally any data transmitted by uplink signals to the wireless MI receiver component (1 17).

[0144] As shown in FIG. 1, the system (100) includes a data transmission (Tx) component (120) configured for data communication with a data reception (Rx) component (122) that together to transfer the recorded data from the mobile DAQ (121) (which include the location (and optionally orientation measurements) and optionally the uplink information to the at least one microprocessor (110) for the estimating of the marker location. The data Tx component (120) is configured for communication with the mobile DAQ (121) and is attached to the mobile platform (108). Depending on implementation, the data Tx component (120) may include transferrable media (e.g., an USB stick) or a cable (e.g., a USB cable or an optical cable), thus the acquired data may be stored locally in the mobile DAQ (121) and downloaded later — after the mission and the movement and measurement processes — via the data Tx component (120). Alternatively, the data Tx component (120) may include communications signals (123) between the data Tx component (120) and the data Rx component (122) that is configured to transfer the recorded data while the movement and measurement process (328) is taking place, thus simultaneously / contemporaneously or in "real time", and the communications signals (123) may travel via a cable connection, e.g., a fibre optic tether (e g., for an underwater rover), and / or a wireless connection, e g., a WiFi link. In alternative implementations, the at least one microprocessor (110) may be included on / in the mobile platform (108) such that the localization processes (338) can be executed locally on the mobile platform (108), for which the magnetic field measurement data (and optionally orientation) from the marker apparatus (102) is transmitted direct to the wirelessMI receiver component (117); and the data Tx component (120) and the data Rx component (122) may be configured to transmit the estimated marker locations, e.g., in real time, to identify the marker locations while the movement and measurement process (328) is taking place.

[0145] As shown in FIG. 1 , the system (100) may include the stationary platform (126) — operating as a "ground multihop relay" — that is configured to receive signals from the markers (102) and to communicate with the data receiver component (122) by sending further communications signals to the data Rx component (122) representing the signals from the markers (102). The further communications signals can transfer recorded data from the marker apparatuses (102) to the data Rx component (122) without needing to use the wireless MI Rx component (117) on the mobile platform (108). The further communications signals may travel via a cable connection, e g., a fibre optic tether (e g., for an underwater rover), and / or a wireless connection, e.g., a WiFi link. The signals from the markers (102) may travel at least partially TTE, and may include Ml signals generated by at least a closest one of the markers (102) to the stationary platform (126), as shown in FIG. 1. The stationary platform (126) may include the magnetic field source (105), thus providing one of the fixed magnetic field sources, thus operating as a b-field localization source as well as a multihop communications relay (for the uplink information from the markers (102) to the microprocessor (110)). The stationary platform (126) may include one of the wireless MI Rx components (117) for receiving the uplink signals from the markers (102), thus operating as the "ground multihop relay". The stationary platform (126) may include one of the wireless MI transmitter components (116) for transmitting the downlink signals to the markers (102). The stationary platform (126) may include a stationary version of the mobile DAQ (121) — thus a stationary DAQ — for acquiring data sent to the stationary platform (126). The stationary platform (126) may include one of the data transmission components (120) for the data communication with the data reception component (122), including for the further communications signals. The stationary platform (126) may include one of the navigation modules (118) that determines the fixed / stationary location of the stationary platform (126), e.g., for use in the inversion process (340) if the magnetic field source (105) of the stationary platform (126) is acting as a fixed station. The stationary platform (126) may be one of thedrones that is parked / stationary during generation of its magnetic field (b) — from only one of the source locations since it is not moving during the measurements of the magnetic fields (b) — then movable for a data gathering phase, including gathering the measurement data from the markers (102) and delivery of that data to the microprocessor (110), which may improve the SNR / speed of the data transmissions. Although not specifically shown in FIG. 1, the magnetic field source (105) of the stationary platform (126) can generate its magnetic field (b) to be detectable / measurable by all or close markers (102), and the wireless Ml transmitter component (116) of the stationary platform (126) can for transmit the downlink signals to the markers (102).Downlink Signals

[0146] As shown in FIG. 1, the system (100) may include the wireless MI transmitter component (116) mount ed / attached to the mobile platform (108). In some implementations, the wireless MI transmitter component (116) can use the same MI antenna as the magnetic field source (105).

[0147] The wireless MI transmitter component (116) may be referred to as a "downlink transmitter" because it provides the downlink information to the marker (102) from the rest of the system (100) — and in particular from the mobile platform (108). The wireless MI transmitter component (116) is configured to transmit the downlink signals (which include wireless downlink signals as described hereinbefore) to the marker apparatuses (102). The downlink signals can travel in any direction from the mobile platform to the marker apparatus (102), not just down: this direction may be upward if the markers are buried in rock / earth above an underground mine tunnel in which the mobile platform is moving.

[0148] The wireless MI transmitter component (116) may include at least one loop antenna (referred to as the "downlink transmit antenna") substantially in a plane perpendicular to an axis that is substantially directed between the mobile platform (108) and the magnetometer (106) in / on the opaque medium (104), e g., when the navigable medium (112) is above the opaque medium (104), the axis may be a substantially vertical axis but not precisely due towind / movement that forms a vertical magnetic dipole (VMD). The downlink transmit antenna may have substantially vertical axis for some applications, e.g., where the magnetometers (106) are substantially below the navigable medium (112), e.g., in a muckpile, in other applications, the downlink transmit antenna may have a substantially horizontal axis, thus forming a horizontal magnetic dipole (HMD), e g., where some / all markers are substantially horizontal to the navigable medium (e.g., in a bench / quarry face). In other applications, the downlink transmit antenna may include two or more loop antennas oriented at respective mutually different orientations (with respective orthogonal axes), including orthogonally, including at two mutually orthogonal orientations or at three mutually orthogonal orientations, e g , when the markers are substantially surrounding the navigable medium, e g., around a shaft / tunnel in an underground mine. The downlink transmit antenna can include a set of electrically conductive coil or loop antennas. As mentioned hereinbefore, the downlink transmit antenna may also be used by the magnetic field source (105) to generate the magnetic fields (b) used for the localization.

[0149] The set of electrically conductive coil or loop antennas of the magnetic field source (105) include an average diameter of between 0.5 m and 5 m, e.g., substantially 1 m.

[0150] The MI antenna magnetic field source (105) can be driven at substantially or approximately 50 watts (W).

[0151] The modulated magnetic fields (b) can include signals that can travel a distance (or range, which includes TTE) using the one or more MI signal frequencies, including the carrier frequencies (fc). The MT signal frequencies can include at least one frequency in the low frequency (LF) ITU frequency band, and / or frequencies between 100 Hz to 1 MHz, between 1 kHz and 10 kHz, between 1kHz and 1 MHz, between 10 kHz and 300 kHz, or between 20 kHz and 200 kHz, or between 35 kHz and 130 kHz, or between 50 kHz and 100 kHz, e.g., substantially 70 kHz.

[0152] The detectable distance provided by the magnetic field source (105) and the coil (702) can be at least 10 meters; greater than 100 meters; greater than multiple or many hundreds of meters; up to substantially 500 meters; between 200 and 900 meters; up to substantially a kilometre; greater than a kilometre; and / or or greater than multiple kilometres.

[0153] The wireless MI transmitter component (116) is configured to generate the downlink signals in at least one downlink channel (which is a modulation channel defined by a FDM carrier frequency or CDM code or TDM timeslot) that is different from the uplink channel defined by the FDM frequency and / or CDM code and / or TDM timeslot of the uplink signals from the marker apparatus (102), thus allowing simultaneous operation of the downlink channel with the uplink channel. The downlink signals may include at least one downlink frequency that is higher than the frequencies of the uplink signals. The downlink signals include a data component, so higher bit rate may be desirable (higher frequency). In addition, more power may be available on the mobile platform (108) than in the marker apparatus (102), so signal loss due to attenuation of higher frequencies in the medium (104) can be overcome. Higher frequencies may increase signal pickup in the marker coil antenna (702). The localization signal may work better with a lower frequency signal having correspondingly lower distortion: in some cases, the lower the frequency, the less distortion there is due to the ground (and there may be less variation from simplified models that account only for a homogenous geology); however, lower frequencies mean less bandwidth for data, lower voltages induced in induction loop antennas, and more capacitance required for resonant systems, so to duplex two signals (in the downlink and uplink channels, with the localization magnetic fields (b)), it can be preferable to have two types of "downlink" signals: first, the information downlink signals (which provide no localization, and are data heavy) as the higher frequency, and second, the localization downlink signals (which provide the localization, and are data light) as the lower frequency. In examples, this difference may be substantially 20 Hz, or it might be substantially 200 Hz or substantially 2 kHz, or substantially 20 kHz.

[0154] When the system (100) includes the wireless MI transmitter component (116), the at least one marker apparatus (102) includes the marker's downlink MI receiver (812) that is configured to receive the wireless downlink signals. The downlink MI receiver (812) is configured to demodulate the downlink signals, and send corresponding downlink commands represented by the downlink signals to the at least one microcontroller (806). The MI Rx (812) and microcontroller (806) are configured to detect a downlink command which may include a preamble with a selected number of cycles of the downlink carrier frequency thatthe downlink MI receiver (812) is configured to lock to. The microcontroller (806) may be configured to recognise the downlink command based on the quasi-unique code ID stored in the microcontroller (806) (memory of the microcontroller (806)) matching a marker ID sent with the downlink command. The downlink command may include data representing (i) what uplink channel to use; and (ii) how long the marker should remain awake (defining a transmit duration), and / or defining a condition for the marker to return to its low-power state

[0155] The downlink commands recognised by the microcontroller (806) may include: a. a WAKE UP command; b. a CHANNEL SELECT command; and / or c. a TRANSMIT TIME command.

[0156] The marker apparatus (102) may be configured to be awoken multiple times by two or more WAKE UP commands, including at mutually different locations, e.g., pre-blast and post-blast, or pre-excavation and post-excavation (including detecting the marker apparatus (102) again in a stockpile and again on a conveyor). In block caving, at least one marker apparatus (102) may be buried in an upper portion of the ore body and the movement of the portion can be repeatedly monitored during excavation by repeatedly localizing the marker apparatuses (102).

[0157] The demodulation process based on the carrier frequency (fc) that the magnetometer (106) uses to detect the modulated magnetic field (b) can also allow for simultaneous and parallel measurement of two or more magnetic fields (b) if the carrier frequencies (fc) from the magnetic field sources (105) are mutually different, or if the respective magnetic field sources (105) are otherwise transmitting on non-overlapping multiplexing channels, e.g., using frequency-division multiplexing (FDM), time-domain multiplexing (TDM) and / or code-division multiplexing (CDM).

[0158] To use the multiplexing channels, the magnetometer (106) is configured to detect the modulated magnetic field (b) and the downlink signals from the two or more source locations simultaneously (thus in "parallel"), and the magnetic field sources (105) at the respectivesource locations are configured to use the mutually different (and substantially different) multiplexing channels (e.g., defined by the carrier frequencies (fc) for their modulated magnetic fields (b)). If the carrier frequencies (fc) differ substantially, the magnetometer (106) might include respective capacitive tuning elements that are used to detect the different carrier frequencies (fc).

[0159] The selected multiplexing process may include frequency-division multiplexing (FDM), time-domain multiplexing (TDM) and / or code-division multiplexing (CDM), with each marker (102) being configured to receive selected multiplexing channel(s) at manufacture (e.g., by hard coding a multiplexing channel into the marker apparatus (102), e g., a selected carrier frequency and / or modulation code) and / or during deployment (e g., by an encoding process described hereinafter), and / or during operation of the process described herein (e g., by downlink signals in MT transmissions from the wireless MI transmitter component (116) of the system (100) described hereinafter).

[0160] When configured for FDM, the respective magnetic field sources (105) have respective frequency channels and are configured / configurable to generate their magnetic fields (b) and downlink signals using respective substantially separated carrier frequencies (fc). Each magnetic field source (105) may be configured / configurable to generate the magnetic fields (b) and downlink signals with at least one carrier frequency (fc) such that different source locations use mutually different carrier frequencies (fc). The carrier frequency (fc) of each magnetic field source (105) may be selected during manufacture ("hard coded"), including by configuration of the magnetic field source (105), e.g., size, inductance, and drive frequency. Alternatively, an available range of carrier frequencies may be set during manufacture, including by the configuration of the magnetic field source (105) and the magnetometer (106), and the carrier frequency (fc) (within the available range) may be selected during an encode markers process (304) at the site by a person / user / operator or by a robotic deployment apparatus, using an encoder device (e g., a standard mine-site encoder, also referred to herein as a "blast encoder") that is configured to transmit a command signal (which may be in the form of a data string) representing the selected carrier frequency (fc) within the available range: the encode markers process (304) occurs prior to or during deployment of the marker apparatus (102) in the medium (104), while the marker apparatus(102) is in electrical communication with the encoder device, or in line-of-sight communication with the encoder device, and before the marker apparatus (102) is attached / seated / placed / buried / submerged on / in the opaque medium (104) and before the marker apparatus (102) enters the low-power state (thus power use is reduced in the marker apparatus (102)). Alternatively, the carrier frequency (fc) for the magnetic field source (105) and the corresponding magnetometers (106) may be selected during the execute mission process (308) by the wireless Ml transmitter component (116) sending the CHANNEL SELECT command to the marker apparatus (102) in the downlink signals. The CHANNEL SELECT command tells the marker apparatus (102) that a carrier frequency (fc) has been selected from the available range, e g., based on a selected carrier frequency (fc) in the CHANNEL SELECT command and / or a random number generator in the marker apparatus (102) and / or a list of the carrier frequencies (fc) in the available range stored in the memory of the marker apparatus (102). The CHANNEL SELECT command may be transmitted with the WAKE UP command.

[0161] The downlink signals may be in any spatial direction, but are always from the mobile platform (108) to the marker (102), and the downlink signals are always wireless signals, travelling by way of the MI transmissions that are wirelessly emitted from the wireless MI transmitter component (116) attached to the mobile platform (108) and wirelessly received by the marker apparatus (102). The downlink signals provide through the earth (TTE) communications because the wireless MI transmitter component (116) is configured to generate the Ml transmissions with appropriate frequency components to travel substantially into the opaque medium (104). The MI signalling may be referred to as comprising "downlink signals" because the mobile platform (108) is often represented as being above the marker apparatuses (102), e g , for buried marker apparatuses (102) and the mobile platform (108) moving above, so the MI signals travel down from the magnetic field source (105) to the mobile platform (108), e.g., as shown in FIGs. 1 , 1 1 and 12; however, the so-called "downlink signals" can equivalently travel in any direction from the magnetic field source (105) to the mobile platform (108), e.g., sideways or up, e.g., in an underground mining operation with the marker apparatuses (102) buried in upholes above an access tunnel inwhich the mobile platform (108) moves, so "downlink" in this disclosure can be in any physical direction, including down, up and sideways.

[0162] In some implementations, the system (100) may select the carrier frequencies (fc) with reference to the spatial separation of the marker apparatuses (102). In such implementations, a memory of a controller of the system (100) — which may be a microcontroller or a microprocessor on the platform (108) or otherwise in communication with the wireless MI transmitter component (116) to control the CHANNEL SELECT command — may include a list of the available channels (based on the available range of carrier frequencies) for the system (100), and the controller of the system (100) may be configured to control adjacent ones of the magnetometers (106) detectable in a selected area / volume of the medium (104) to have mutually different channels in the CHANNEL SELECT command

[0163] As a result of the encode markers process (304) or the CHANNEL SELECT command (depending on whether the channels are hard coded or soft coded), the marker apparatus (102) is programmed with channels, e.g., the carrier frequency (fc), to receive the magnetic field (b) and the downlink signals. The channel may thus be unique to each marker apparatus (102) and may be used to identify which measurements belong to which the magnetometer (106). The WAKE UP command may include the CHANNEL SELECT command, so the marker apparatuses (102) may wake up in response to the WAKE UP command, and the carrier frequency fc may be allocated at this point. The CHANNEL SELECT command may be sent with the TRANSMIT TIME command.

[0164] The TRANSMIT TIME command represents the selected field generation duration (also known as the "transmission time"), which may be a duration from the receipt of the TRANSMIT TIME command, to begin recording the magnetic fields (b), and representing the selected field generation delay time. The field generation duration and the field generation delay time may be selected according to a localization plan for the site. The field generation delay time may be effectively zero, to control the marker apparatus (102) to commence recording the localization signal immediately, or the field generation delay time may be at least 1 minute, 1 hour, 1 day or 1 week, e.g., such that the marker apparatus (102)commences recording the magnetic field (b) before or after an expected event, e g., a blast defined by a blasting plan.

[0165] The FDM may be sufficient for low-density marker deployments, but higher density deployments may require TDM / CDM if spectrum in the frequency domain within a specific spatial region is exhausted.

[0166] When configured for CDM, the marker apparatuses (102) are configured with the memory storage (822) to store and / or receive a channel code representing a plurality of carrier frequencies (using a spread spectrum process), and to demodulate the magnetic field (b) and / or the downlink signals according to the channel code, and the CHANNEL SELECT command instructs the marker apparatus (102) to select a channel code instead of just one carrier frequency (fc), and the controller of the system (100) may be configured to select the mutually different ones of the available channels to send in the CHANNEL SELECT commands based on a list of the available channel codes for the deployed marker apparatuses (102).

[0167] The modulated magnetic field (b) and the downlink signals may each include the code or identifier (ID) that identifies each magnetic field source (105) and / or source location. When configured for CDM, each magnetic field source (105) transmits the codes or identifiers (ID) to allow the recorded magnetic field measurements to be allocated to the correct each magnetic field source (105), including when performing the inversion process (340).

[0168] When configured for TDM, each magnetic field source (105) has a separate multiplexing channel by generating its magnetic field (b) at a mutually different time slot selected in the same processes for selecting / setting the carrier frequencies (fc).

[0169] In some applications, FDM / CDM may be more desirable than TDM because it may be difficult to maintain a global time (used in TDM) between a plurality of the magnetic field sources (105). FDM may be more desirable when there is high attenuation of the magnetic field (b) and / or the uplink signals from the markers apparatuses (102) (which can be common in rock / soil / earth and air, e.g., when the magnetometer (106) is operating in the near fieldregion or zone of the marker apparatuses (102)), thus reducing the magnetic field detection range of the magnetometer (106) required for frequency reuse.

[0170] The multiplexing process may include FDM, TDM and / or CDM in combination, e g., a layered stack of a base FDM with slowly modulated (as in several carrier cycles) data / code on top. At a base level, the channels may be split in frequency, but each channel may be shared by mutually different vehicle apparatuses (102) using respective different codes. The channels may further be spread spatially: as the magnetic fields (b) and / or the downlink signals are highly attenuated, pairs of source locations with matching / overlapping carrier frequencies (fc) may be separated by distance that is sufficient that the magnetometer (106) does not measure the localization signals from both source locations in the pair at the same time (or such that the localization signal from one of the pair is below a selected SNR), thus allowing reuse of the spectrum.

[0171] In some implementations, the magnetometer (106) may be configured to detect the magnetic field (b) and / or the downlink signals with carrier frequencies (fc) up to substantially 300 kHz, such that the carrier frequencies can span from substantially 1 kHz to substantially 300 kHz, or from at least substantially 0.001 kHz, 0.01 kHz, 0. 1 kHz or 1 kHz, or up to substantially 300 kHz, or between 1 kHz and 10 kHz. In some implementations, the magnetometer (106) and the DAQ component (114) have a frequency resolution of at least substantially 1 Hz or at least substantially 10 Hz or 20 Hz, for example by digitising the downlink signals at up to substantially 10 MS / s or up to substantially 100 MS / s. Thus the carrier frequency separation when configured for FDM between adjacent ones of the vehicle apparatuses (102), or vehicle apparatuses (102) within the magnetic field detection range of the magnetometer (106), can be substantially 1 Hz, 10 Hz or 20 Hz or greater. In examples with relatively few vehicle apparatuses (102), the carrier frequency separation can be thousands of hertz, from 2 kHz to 10 kHz.

[0172] The controller of the system (100) — described hereinbefore — may be configured to transmit signal s / data representing the location codes (which may include the sequence codes) to the marker apparatus (102) at the same time as the magnetic fields (b) are being generated, thus allowing each marker apparatus (102) that detects the magnetic field (b) from a certainsource location to also detect / receive and store a certain location code uniquely identifying that certain source location in at least that mission or instance of the localization process (338). This storing of the location codes matched to the respective magnetic field measurements in each marker apparatus (102) may allow the system (100) to execute the localization process (338) without needing to match the magnetic field measurements with the respective source locations based on time stamps (time measurements) made in the marker apparatus (102) and the above-ground components (the tracking module, including the navigation module (118) and / or the remote location tracking system), which may mitigate a source of uncertainty in the localization process (338). The system (100) can transmit the location codes in the modulation of the magnetic fields (b) and / or in the downlink signal to uniquely identify the source location for each magnetic field measurement in the data stored in the marker component (102), e g , recorded in the DAQ component (1 14).Microprocessor (110)

[0173] The at least one digital microprocessor (110) may include one or more processing units that are remote from the measurement locations and that access machine-readable memory with code that controls the processing units to determine / calculate the marker location by executing the localization process (338). The at least one digital microprocessor (110) may include an application specific integrated circuit or a field programmable gate array configured to perform one or more steps of the localization process (338).

[0174] The at least one digital microprocessor (110) receives the (timed / identified) source locations (e.g., as position-orientation-time vectors, and / or the location codes representing the source positions and / or orientations) that have been recorded / logged by the mobile DAQ (121) and the (timed / identified) magnetic field (b) measurements (e g., as field-time vectors) (and optionally field vectors and phases for the vector and coherent vector magnetometers, and optionally accelerometer / compass measurements) that have been recorded / logged by the marker DAQ (114).

[0175] In some implementations, the at least one digital microprocessor (110) may include at least one processing unit in the marker DAQ (114), e.g., for performing one or more of stepsof the localization process (338), and / or may include at least one processing unit that is remote from the marker DAQ (114) but connected using digital communications (e.g., a wireless data link or a wired data link that is connected after the execute mission process (308)). The remote microprocessor may include a GPU / CPU on a laptop or personal computer, or a server computer, or at least one cloud processor in a computing cloud, e g., provided by Microsoft Azure or Amazon Web Services. Optional processing could be onboard the marker apparatus (102) and / or the mobile platform (108), and — if it's on the marker apparatus (102) — it is communicated out wirelessly, e g., by a single or multi-hop data uplink.

[0176] The digital microprocessor (110) is at least one physically discrete device that may include a microcontroller, e.g., in the marker DAQ (114), that handles the control of the analog to digital converter that accepts the analog information from the magnetometer coils, then logs digitised flux measurement to non-volatile memory. The mobile DAQ (121) records the measurements from encoders (119) in the gimbal (if present). The digital microprocessor in the mobile DAQ (121) may log the stream of data from the navigation module (118), or the navigation module (118) may include its own digital microprocessor with non-volatile memory for logging this stream of data The data from the marker DAQ (114), the mobile DAQ (121) and the navigation module (118) or the remote location tracking system may be transmitted to the separate computing system for performing the inversion process (340) in "post processing" by another physically discrete set of data processing units / processors configurable or configured to execute stored program instructions and operate upon data in accordance therewith, such as a digital microprocessor, e.g., at least one general processor unit and / or graphics processing unit (GPU). Thus in embodiments there may be at least two physical digital microprocessors. The data reduction process (500) and the inversion processes (340) may be performed after the mission process (308), e.g., using a set of remote data processing units / processors, which may allow for improved GNSS correction, either by using INS data or getting better ephemeris for PPK, compared to relying on real-time correction. Using the at least one remote processor may allow for unconstrained computational power.Marker Survivability

[0177] The marker apparatus (102) includes the shell (714) that surrounds the magnetic field receiver, including the marker MI antenna, and the electronic components (800), including the power source, e.g., as shown in FIG. 7.

[0178] The shell (714) is a housing, case, frame and / or support structure that mechanically houses, carries, protects and / or supports at least pressure and water-sensitive elements of the blasting-related device. The pressure and water-sensitive elements include the device-based electronic elements, including the electronic components (800), e.g., the device power source, the device control unit, and the device-based MI coil driver.

[0179] The shell (714) may include a hard shell or housing. The hard shell provides impact protection and / or force dispersion (of any externally applied force to the marker) in order to protect the electronic components (800) and the coil (702) inside

[0180] The shell (714) may also provide chemical resistance and abrasion resistance.

[0181] The shell (714) may be substantially formed of a low / non-conductive material and / or low / non-permeable material, e.g., plastic or fibreglass reinforced plastic, e.g., Nylons, POM (Delrin), Fibreglass composites, Polyethylene, and / or Polycarbonate. The shell (714) may be extruded or injection molded, and may be machined from an extruded / cast base.

[0182] The overall size of the shell (714) is substantially less than the wavelengths in the modulated magnetic fields (b), e.g., the maximum length of the shell (714) along any of its axes may be substantially less than the wavelengths, e.g., at least 10, 100, or 1000 times less. Thus the practical size of the marker MI antenna is much less than the length of the wavelength the magnetic field generated, and the marker MI antenna can be approximated to be receiving at a point in the processes described herein.

[0183] The shell (714), and thus the marker apparatus (102), may have a substantially cylindrical shape: the shell (714) may include a length of pipe forming a curved wall around the marker apparatus (102); and the ends of the shell (714) may include removably attachable caps (716), e.g., substantially circular caps, e g., caps with threads for screwing into the pipe,e.g., as shown in FIG. 7. One cap (716) may be manually removable during deployment by a person / operator in order to plug in the blast encoder to communicate with the microcontroller (806) as described hereinbefore. Alternatively, if the marker apparatus (102) is encoded wirelessly, or not during deployment, the caps (716) may be both sealed, and shell (714) may be completely encapsulated with no removable cap.

[0184] The shell (714) may have a substantially cylindrical shape, e.g., with a substantially 90-mm outer diameter and a substantially 100 to 200-mm length.

[0185] Having a substantially cylindrical shape may be easier to make and receive the marker antenna, the PCBA (708) and the battery (706), e.g., as shown in FIG. 7.

[0186] The length ratio (aspect ratio) of the coil (702) may affect its performance as a magnetic field receiver, thus there may be a trade-off between a longer shape for better core performance vs a shorter shape for better survivability.

[0187] Long skinny devices may perform poorly in survivability in some applications, e.g., by being more likely to snap in half, so the cylindrical shape may be selected to be a squat cylinder or substantially spherical. The shell (714) may have a substantially spherical shape to provide a minimal volume: surface ratio.Mobile Platform (108)

[0188] The mobile platform (108) (e.g., the vehicle) is configured to move / carry the mobile magnetic field source, the wireless MI transmitter component (116) and the wireless MI receiver component (1 17), between the plurality of source locations (which may also be referred to herein as "stations"), including while the magnetometers (106) are making the magnetic field measurements, i.e., making the magnetic field measurements (e.g., multiple magnetic field measurements, or a multiplicity of magnetic field measurements) while the vehicle is moving at the non-zero speed. In operation, the mobile platform (108) moves through the navigable medium (112) (e.g., space, air or water) to make the source transmissions at the multiple locations relative to the obscured marker apparatuses (102) and the or each marker (102) makes the magnetic field measurements while the mobile platform(108) is moving, i.e., while a speed of the or each vehicle is non-zero in the reference frame of the marker apparatuses (102) and the opaque medium (104).

[0189] The mobile platform (108) includes a frame or body that carries a power or energy source, and locomotion elements. The mobile platform (108) includes a prime mover, motor or engine. The mobile platform (108) is configured for locomotion (i.e., the ability to move from one place to another) such that it can be selectively / selectably deployed, positioned, directed, guided, manoeuvred, piloted, and / or driven to multiple physical locations during at least the move mobile magnetic source process (330).

[0190] The mobile platform (108) may be an airborne platform configured for air travel, a land-based mobile platform configured for land travel, or a waterborne platform configured for on-water or submersible travel, e.g., an aircraft drone, a boat, an underwater drone, and / or a land vehicle (with wheels).

[0191] The mobile platform (108) may include a crewed vehicle or an uncrewed vehicle. The mobile platform (108) can include manual controls for a human occupant. The mobile platform (108) can include a remote-control unit for remote control of the mobile platform (108). The mobile platform (108) can include an autonomous control unit for autonomous control of the mobile platform (108).

[0192] The vehicle may be an air vehicle (e.g., a helicopter, a drone or Remotely Piloted Aircraft (RPA)), a land vehicle, or a water vehicle. The RPA may include an uncrewed airborne drone or UAV, being fixed-wing or multirotor or other configuration. The mobile platform (108) may include one or more types of control systems, including: an on-board pilot control system, a remote-piloted control system, an autonomous control system, and / or an adaptive / leaming control system. The vehicle may include a plurality of rotors, e.g., four or more. The vehicle may have a significant payload capacity, e.g., substantially 0.5 kg, between 0.5 and 1.5 kg, between 0.6 and 1.1 kg (e.g., substantially 0.9 kg), between 1 and 5 kg (e.g., substantially 3.2 kg), between 5 and 10 kg.

[0193] The vehicle may be a land based automated and / or autonomous vehicle (e.g., a remotely piloted terrestrial rover (RPTR) and / or autonomous land based drone).

[0194] As shown in FIG. 2, the system (100) may include a tow member with one or more mechanical linkages (202) between the mobile platform (108) and the wireless MI receiver component (117) or the magnetic field source (105) to provide a substantial spatial distance between the or the magnetic field source (105) or the wireless MI receiver component (117) (which includes sensitive magnetic-field sensors and associated electronic circuits) and the mobile platform (108) (which can be a source of magnetic-field noise, electromagnetic interference (EMI) and / or vibration). Including the tow member in the system (100) allows for the wireless MI receiver component (117) to make the measurements further away from the mobile platform (108), which may be a source of the electromagnetic / magnetic noise. Including the tow member in the system (100) allows for the magnetic field source (105) to be separated from the mobile platform (108), e.g., into the water under a boat vehicle. The tow member may also allow the wireless MI receiver component (1 17) to be clear of any landing skids and / or obstacle avoidance landing cameras of the mobile platform (108). The tow member may be referred to as providing a "tow" mechanism because the wireless MI receiver component (117) or the mobile platform (108) is towed by the mobile platform (108), although the wireless MI receiver component (117) or the mobile platform (108) need not be behind the mobile platform in a travel direction. The tow member may include a rigid structure forming a fixed relation to hold the wireless MI receiver component (117) or the mobile platform (108) in a fixed spatial relation to the mobile platform (108) during operation (the measuring and the movements between the measurement locations). Alternatively, instead of the rigid structure, the tow member may include a flexible structure forming a flexible relation to hold the wireless MI receiver component (117) or the mobile platform (108) at the substantial spatial distance from the mobile platform (108) while allowing relative spatial movement of the mobile platform (108) and the wireless MI receiver component (117) or the mobile platform (108): in this alternative, the system (100) includes a relative pose measurement system to measure the pose between the mobile platform (108) and the wireless MI receiver component (117) or the mobile platform (108) during the operation (at least during the measuring at the measurement locations) since the relative spatial relationship is not fixed during the operation. The flexible tow structure may include a rope / chain / line that sets a maximum spatial separation equal to the substantial spatial distance but that can be coiled / folded for landing / storage: the rope / chain / line has a predefinedlength in tension but can be shortened by compression. The flexible tow structure may include a pole (of the mechanical linkages (202) connected beneath the mobile platform (108) by a gimbal that allows rotation and swing of the pole relative to the mobile platform (108) while the pole has a predefined length in tension and in compression.

[0195] Having the tow member allows the navigation module (1 18), which may include the GNSS receiver and / or the LiDAR SLAM system, to be above the mobile platform (108), while allowing the wireless Ml receiver component (117) or the mobile platform (108) to be substantially below the mobile platform (108), thus mitigating the mobile platform (108) blocking navigational signals to the navigation module (118), which may include satellite signals, from one direction (e.g., form above) and mitigating the mobile platform (108) blocking the uplink signals from the other opposite direction (e g., from below). Having the rigid structure (of the tow member) or the relative pose measurement system allows determination (respectively by static control or dynamic measurement) of the location, and optionally orientation (for vector and phasor measurements), of the wireless MI receiver component (117) or the mobile platform (108) from the location, and optionally orientation, of the navigation module (118) and the relative pose of the wireless MI receiver component (117) or the mobile platform (108) attached to the mobile platform (108) by the tow member. In an example, by using a rigid pole between the platform (108) and the wireless MI receiver component (117) or the mobile platform (108), the pose measurement may be simplified to measuring the orientation of the wireless MI receiver component (117) or the mobile platform (108) relative to the navigation module (118), which may provide a global position and orientation (P&O). In another example, a tow rope / chain may allow more movement of the wireless MI receiver component (117) or the mobile platform (108) relative to the mobile platform (108) (including orientation and a direction affected by travel speed), in which case the relative pose measurement system may measure relative P&O in 6 dimensions (including 3 positional and 3 orientational).

[0196] For a land-based platform, the tow member may include a rigid or jointed boom extending horizontally from the platform, e g., fixed rigidly to a frame of the vehicle, such as the vehicle's body / chassis, by mechanical fasteners / welds. The rigid / jointed boom may be attached and configured to hold the wireless MI receiver component (117) or the mobileplatform (108) at the substantial spatial distance away from the mobile platform (108) and close to but not touching the boundary / surface, e.g., the ground, e.g., substantially 0. 1 m to 10 m, e g , substantially 1 m from the ground.

[0197] As shown in FIG. 2, the tow member may include a mechanically flexible mechanism that allow the tow member to change shape (including its linear length) under control of the system (100) when the mobile platform (108) is parked / stored. When the system (100) includes the pole, the pole may include a flexible joint (or "knee") 204 between ends of the otherwise rigid pole, thus forming two of the linkages (202) joined at the knee (204). The knee (204) is configured to be locked such that the pole is rigid, e.g., straight, while the mobile platform (108) is moving between the measurement locations (e.g., when the mobile platform (108) is an air vehicle) so that the magnetometer (106) orientation can be measured accurately. The knee (204) is configured to unlocked after making the measurements, e g., when the air vehicle lands, thus allowing the pole to fold at the knee (204), allowing the mobile platform (108) and magnetometer (106) to land and be stored / transported in a compact manner. The knee (204) may include a cable that is pulled tight to lock the knee (204) by an actuator, e.g., including a servo-type motor controlled by the control system of the mobile platform (108); alternatively, the knee (204) may include a hinge in the form of a mechanical bearing, e.g., releasably locked by a pin that engages with a lever actuated by a servo-type motor controlled by the control system of the mobile platform (108).

[0198] The system (100) may include a protective shoe mounted to / on the wireless MI receiver component (117) or the mobile platform (108) to protect the wireless Ml receiver component (117) or the mobile platform (108) from impact when the mobile platform (108) approaches a solid object / surface, e.g., when landing / parking or moving close to a wall / muckpile The shoe may include a base portion mounted / attached to the base / underside of the wireless MI receiver component (117) or the mobile platform (108). The shoe is configured to protect the wireless MI receiver component (1 17) or the mobile platform (108) from impact when landing, so is on the face facing substantially towards the ground during the measurements (e g., on the bottom of the wireless MI receiver component (117) or the mobile platform (108)). The shoe may be configured to tip the wireless MI receiver component (117) or the mobile platform (108) onto its side when the shoe touches the solidobject / surface, when landing and being stored / transported, thus guiding the wireless MI receiver component (117) or the mobile platform (108) away from the solid object / surface to protect the wireless MI receiver component (117) or the mobile platform (108)

[0199] The system (100) may include both the knee (204) and the shoe, or just one of the knee (204) and the shoe, in different embodiments / applications.

[0200] In one or more applications, the folding knee (204) (and optionally the shoe) may improve safety through a simpler take-off and landing because the folding payload makes landing easier. For example, an example air vehicle may descend substantially vertically to land, in contrast to having a pole without a knee (a rigid pole) which would require descend at a substantial angle to lay out the pole Allowing a vertical landing may be preferable if the air vehicle is configured to have a simple vertical landing in its predefined return to home (RTH) failsafe, initiated when the air vehicle loses its control system connection / link — with a rigid pole, an air vehicle may encounter upwards resistance as the magnetometer (106) touches down, which may be interpreted as the airframe touching down, causing a crash. In one or more applications, it may be advantageous to not have to reprogram / reconfigure the mobile platform (108) in order to operate with the wireless MI receiver component (117) or the mobile platform (108): the pole with the knee (204) may thus allow the system to be "drone-agnostic".

[0201] The tow member may include a telescopic strut between the wireless MI receiver component (117) or the mobile platform (108) and the mobile vehicle (108). The telescopic strut may include a gas with sufficiently high pressure to extend the telescopic strut to a maximum length (thus providing the substantial spatial distance) during the measurements (e.g., during flight), but sufficiently low pressure to allow the telescopic strut to be compressed to a minimum length for landing and storage, e.g., by exerting a lower extension force on the strut that a downward force applied by the mobile platform (108) when landing and pressing the magnetometer onto the ground / landing platform. When the mobile platform (108) is the airborne platform, instead of the knee and the shoe (which provide for reorientation of the wireless MI receiver component (117) or the mobile platform (108) on landing and for storage), the telescopic strut may include a passive gas strut collapsed by theweight of the airborne platform (including all components carried by the mobile platform). Alternatively, including for an airborne, land-based and / or water-borne platform, the telescopic strut may have powered extension and retraction by the system (100) including a pressure pump / controller to switch between the low pressure and the high pressure in the strut, e g., controlled by the control system of the mobile platform (108).Overall Process (300)

[0202] As shown in FIG. 3, the system (100) is configured to perform an overall process (300) that includes the following processes: a. the calibrate magnetic field source process (302); b. the calibrate marker magnetometer process (303) c. the encode markers process (304); d. the path generation process (306); e. the execute mission process (308), which includes: i. the downlink processes (310), ii . the marker processes (318), iii. the move process (328); iv. the uplink process (324); and f. the localization process (338), which includes: i. the inversion process or processes (340), and ii. the estimate markers' P&O process (342).

[0203] The calibrate magnetic field source process (302) includes the strength or moment (m) of the magnetic field source (105) being measured / set, e.g., during manufacture, prior to theexecute mission process (308). Since the inversion process (340) may optionally use one or more calibration values of the magnetic field source (105) to improve precision, the magnetic field source (105) may be configured to generate the magnetic fields (b) with a selected strength or moment (m), defined by the one or more calibration values, in the calibration process (302). The one or more calibration values include a selected value and / or a selected range of values (which may be referred to as a "calibrated range"), and the inversion process (340) may use the selected strength or moment (m) with the mathematical model when numerically estimating the location of the magnetometer (106).

[0204] The calibrate marker magnetometer process (303) includes the sensitivity (K) of the magnetometer (106) being measured / set, e.g., during manufacture, prior to the execute mission process (308). Since the inversion process (340) may optionally use one or more calibration values of the magnetometer (106) to improve precision, the magnetometer (106) may be configured to measure the magnetic fields (b) with the calibrated / selected sensitivity (K), defined by the one or more sensitivity calibration values, in the calibration process (303). The one or more sensitivity calibration values include a selected set of values and / or a selected range of values (which may be referred to as a "calibrated sensitivity range"), and the inversion process (340) may use the selected of the sensitivity (K) with the mathematical model when numerically estimating the location of the magnetometer (106) . In general, the sensitivity (K), corresponding to K in the Appendices, includes the 3x3 matrix of values, as described hereinbefore, since the magnetometer (106) can be a 3-axis magnetometer where the alignment / orthogonality of the axes is also calibrated in the calibrate marker magnetometer process (303); however, if the 3 axes of the magnetometer (106) are substantially orthogonal, or if the orthogonality is not calibrated, then the sensitivity (K) includes a 3x3 diagonal matrix with one scalar sensitivity for each axis; alternatively, if the magnetometer (106) has only one axis, then the sensitivity (K) includes a 3x3 matrix where all elements are zero except one (this can be referred to as a "scalar sensitivity"), wherein the scalar sensitivity value is in the 1,1 position (when the magnetometer axis is defined to be its x-axis). The calibrate marker magnetometer process (303) for a total field magnetometer is generally the simplest, not requiring marker alignment to the field. The calibrate marker magnetometer process (303) for a single axis coil magnetometer is relatively simple,generally generating only one value / number, for which it is assumed that the axis is aligned to the field in a used calibration apparatus. The calibrate marker magnetometer process (303) for a triaxial magnetometer requires the magnetometer (106) to be rotated in a known field, e.g., in three known orthogonal orientations, or to be calibrated using three external orthogonal field sources with a constant magnetometer (106) orientation. The calibrate marker magnetometer process (303) for a phasor magnetometer requires a phase shift calibration in addition to the calibration of each axis as for the triaxial magnetometer.

[0205] The calibrate magnetic field source process (302) and the calibrate marker magnetometer process (303) are generally performed in a factory or perhaps on the truck where a known magnetic field can be generated. The calibrate magnetic field source process (302) and the calibrate marker magnetometer process (303) are generally performed on the magnetometer (106) assembled and fixed within the marker apparatus (102), generally after manufacture / assembly of the electronic components (800) into the marker apparatus (102).

[0206] The path generation process (306) includes generating an intended path (124) for the mobile platform (108) (e.g., vehicle) using a planning system, e.g., a drone controller.102071 The intended path (124) may include two or more passes past the expected marker locations, including: a. a first pass to transmit the CHANNEL SELECT commands to the marker apparatuses (102) which may include approaching the expected marker locations within the downlink distance but not necessarily within the magnetic field detection range of the marker’s magnetometer (106); b. a second pass (or two passes) to transmit the WAKE UP and TRANSMIT TIME commands, possibly within the downlink distance but not necessarily within the magnetic field detection range of the magnetometer (106); c. a third pass to generate the magnetic fields (b) and receive any data uplink signals, representing the magnetic field measurements made during the thirdpass, this time within the magnetic field detection range of the magnetometer (106); d. a fourth pass to re-transmit / generate the magnetic fields (b) and receive any uplink signals from any marker apparatuses (102), representing the magnetic field measurements made during the third pass and fourth pass, for which the localization process (338) did not generate a sufficiently clear / precise location, e.g., by moving even closer to expected marker locations in a blasting plan; and e. if necessary, a fifth pass to receive data uplink signals representing the magnetic field measurements made during the fourth pass.

[0208] In the move and measurement process (328), the measurement data (from the magnetometer (106)) can be sent up the uplink channel in the same pass as the measurement magnetic field (b) is sent down; alternatively, all / part of the measurement data can be sent up the uplink channel on a subsequent pass, e.g., due to the wireless MI receiver component (117) being out of range on the first pass, the marker (102) not having enough time to process and transmit the measurements during the first pass, and / or the uplink channel using the same frequency / time slots / bands as the modulated magnetic field (b) or the to the wireless MI transmitter component (116) (i.e., not being duplex). The measured magnetometer orientation, including the IMU and compass data from the "IMU" accelerometer (818) and / or the "compass" magnetometer (820), is generally constant throughout the mission, and thus is sent up the uplink channel only once per mission.

[0209] The move and measurement process (328) includes the mobile platform (108) executing the mission by following the intended path (124) and the or each magnetometer (106) in the markers (102) making the magnetic field measurements while the speed of the or each source (and thus the or each corresponding mobile platform (108)) is substantially nonzero or non-zero, e g., the substantially non-zero speed can include from slightly above zero meters per second (m / s) to substantially 30 m / s, including from above zero to 25 m / s, including from above zero to substantially 3 to 4 m / s (e.g., for a multi-rotor drone, e.g., formining or quarrying operations), and substantially 8 m / s to substantially 25 m / s (e.g., for a fixed wing drone, e.g., for linear operations, e.g., along a ditch or pipeline).

[0210] The downlink processes (310) include the wireless MI transmitter component (116) generating the wireless downlink signals, including: a. sending the CHANNEL SELECT command in the CHANNEL SELECT process (312); b. sending the WAKE UP command in the WAKE UP process (314); and c. sending the TRANSMIT TIME command in the TRANSMIT TIME process (316).

[0211] In the downlink processes (310), the mobile platform (108) follows the intended path (124) such that the at least one marker apparatus (102) is within the downlink distance of the wireless MI transmitter component (116). The intended path portion during the downlink processes (310) may differ from the intended path portion during the move and measurement process (328): e g., the intended path portion during the move and measurement process (328) may carry the mobile platform (108) substantially closer to the expected marker locations or with more passes, e.g., closer to the surface, than during the downlink communications processes (310).

[0212] The move and measurement process (328) includes the following, repeated iteratively for each source location: a. the move mobile source process (330), moving along the intended path (124), followed by b. on the mobile platform (108) or the stationary platform (126), a generate magnetic field process (331) at the next source location along the intended path (124) when the magnetic field source (105) is generating the magnetic field (b);c. the measurement processes corresponding to the current source location (without necessarily stopping), including: i. in the markers (102), the record measured magnetic field (b) process (332) for recording the magnetic field (b) corresponding to the current source location — and optionally (not shown in FIG. 3) recording the unique location code / ID if received by the marker (102) while the magnetic field measurement is being made, ii. on the mobile platform (108) or the stationary platform (126), the record mobile source position process (334), including the navigation module (118) or the remote location tracking system recording the source location at the same time as the marker (102) is recording the magnetic field (b) — and optionally (not shown in FIG 3) transmitting the unique location code representing this recorded source location to the markers (102), and / or optionally (not shown in FIG. 3) receiving and recording the magnetic field measurements while at the source location (in "real time") via the uplink channel, and / or optionally (not shown in FIG. 3) receiving and recording an identifier ("Record ID"), whichis also stored in the marker apparatus (102) with the magnetic field measurements (to identify them), while at the source location (in "real time") via the uplink channel — various processes for matching the source-sensor pairs are described hereinafter in the Data Reduction Process (500) and the Inversion Process (340); and iii. on the mobile platform (108), the record airframe / source orientation process (336) for recording the source orientation at the same time as recording the source location.

[0213] Alternatively or additionally, if the system (100) includes a fixed magnetic field source, the receiving / determining of the two or more magnetic field measurements may include using at least one of the at least one magnetometer (106) attached to the marker (102) receiving / determining the MI magnetic field (b) from the fixed source. There is no need tosimultaneously measure the location and pose of the fixed source at the measurements times of the magnetometer (106) because the location and pose of the fixed source does not change during the measurements.

[0214] The at least one magnetic field source (105) generates the magnetic fields (b) at the plurality of source locations while the measurements are being made, and the corresponding tracking module measures these source locations at the same times as the measurements are being made.

[0215] The mobile DAQ component (121) and the stationary DAQ are each configured for recording / receiving / storing / logging the location measurements (i.e., source locations) while the marker DAQ component (114) synchronously records / receives / stores / logs the magnetic field measurements.

[0216] The determining / pairing / matching of the two or more measurement locations may include: receiving / determining respective magnetic-field-measurement times when the magnetic field measurements are / were measured in the marker DAQ component (114) (e.g., using time stamps recorded with the magnetic measurements, e.g., in a magnetic-field v. time file); and determining the respective locations of the magnetic field source (105) at the magnetic-field-measurement times from location tracking data representing the location of the magnetic field source (105) over time using the tracking module, e.g., the navigation module (1 18) and / or the remote location tracking system (e g., a satellite or visual or infrared tracking system), with sufficient resolution for recording the flight path of the mobile platform (108) (drone) with time stamps recorded with the 3D locations, e g., in a 3D location v. time file. Alternatively or additionally, the determining of the two or more measurement locations may include: receiving / determining the respective location codes (which may include the sequence codes) that uniquely identify the source locations for the inversion process (340), wherein the location codes are transmitted to the marker apparatus (102) (and e g., recorded in the DAQ component (114)) in the modulation of the magnetic fields (b) and / or in the downlink channel at the same times that the magnetic fields (b) are respectively measured / sensed by the magnetometer (106) (thus uniquely identifying the source location for each magnetic field measurement in data in the marker component (102)). Alternativelyor additionally, the determining of the two or more measurement locations may include receiving and recording the magnetic field measurements while at the source location (in "real time") via the uplink channel, and / or receiving and recording an identifier ("Record ID") that is also stored in the magnetometer (102) with the magnetic field measurements (to identify them) while at the source location (in "real time") via the uplink channel. The various processes for matching the source-sensor pairs are described hereinafter in the Data Reduction Process (500) and the Inversion Process (340).

[0217] The inversion process (340) includes: a. the at least one digital microprocessor (110) receiving the magnetic measurements from the markers (102) and matching location and orientation measurements for the magnetic field source (105) and optionally marker orientations from the markers (102); b. the at least one digital microprocessor (110) optionally correcting the location measurements and optionally orientations using the data reduction process (500); and c. the at least one digital microprocessor (110) applying the mathematical model to generate the 3D location (and optionally the orientation) of the at least one marker apparatus (102).

[0218] The data reduction process (500) includes using corrections data (e.g., GNSS) received from a corrections service or a GNSS base station or the INS (which includes the kinematics processing), and / or the at least one digital processor — GNSS typically uses the terms RTK or PPK as the data-processing processes that take a source of corrections, and INS can be used to supplement / aid / filter the RTK or PPK (e.g., reject satellite measurements that say the vehicle moved drastically when the accelerometers said the vehicle was static) using a data processing component that outputs either a stream or file of positions and orientations of the magnetic field source (105) for the inversion process (340).

[0219] The record measured magnetic field (b) process (332) includes: determining two or more measurements ("magnetic field measurements") of the magnetic field (b) using the magnetometer (106) attached to the marker (102), wherein the magnetic field (b) is generated by the magnetic field source (105) in / on the mobile platform (108) — in the generate field process (331), wherein the marker apparatus (102) is stationary with respect to the opaque medium (104), which may have the surface, e.g., including earth / rock / ice / water, which may include being buried or submerged in the medium (104), wherein the marker apparatus (102) is stationary relative to its surrounding portion of the medium (104) so that the marker apparatus (102) moves with the medium portion if the medium portion moves.

[0220] The localization process (338) includes receiving the two or more magnetic field measurements from the record measured magnetic field (b) process (332).

[0221] The record source position process (334) includes determining (e g., measuring) the two or more locations ("source locations") of the magnetic field source transmissions in three orthogonal dimensions (3D), thus determining the locations of the magnetic field source (105) when the magnetic field measurements are / were determined, wherein the source locations may be in the medium (104) or outside the medium (104) (in which the marker (102) is buried) — wherein the mobile platform (108) is configured to move relative to the marker apparatus (102) in the medium (104) and / or outside the medium (104), which may include on the surface of the medium (104) (e.g., for earth / rock / ice or water) and / or flying / floating substantially off the surface — e.g., above a mine bench or along a mine tunnel.

[0222] The localization process (338) includes receiving the two or more source locations from the record mobile source position process (334).10223 ] The determining of the two or more source locations may include: a. determining (e.g., measuring) locations of the mobile platform (108); b. determining (e g., measuring) a relative location of the magnetic field source(105) to the mobile platform (108); andc. estimating the two or more source locations on numerical addition / subtraction of the locations of the mobile platform (108) and the relative location.

[0224] The inversion process (340) includes numerically estimating (e g., using an iterative process, and using the at least one microprocessor (110)) the location of the magnetic field sensor / magnetometer (106) in the marker (102) in the three orthogonal dimensions (3D) using : a. the two or more magnetic field measurements; b. the two or more source locations; and c. a mathematical model representing a magnetic dipole of the magnetic field source (105).

[0225] As the magnetic field sensor / magnetometer (106) is in the marker apparatus (102), the estimated location of the magnetic field sensor / magnetometer (106) is also an estimated marker location.

[0226] The marker processes (318) includes: a. a control / measure magnetometer orientation process (322) in which the orientation of the marker magnetometer (106) can be control I ed / measured, as described hereinbefore, and b. the uplink process (324) for transmitting the measured magnetic fields (b) and the controlled / measured orientation of the marker magnetometer (106) for use in the inversion process (340).

[0227] The uplink process (324) — which may include the multihop communications process — includes the TTE MI transmitter of the marker apparatus (102) transmitting the uplink information (described hereinbefore) to the microcontroller (1 10), including through the earth, and to the wireless MI receiver component (117) of the mobile platform (108) and / or of the stationary component (126), optionally via the wireless Ml multihop signals (130). The uplink information is transmitted through the medium (104) such that themeasured magnetic fields (b), and optionally the measured magnetometer orientation and / or location codes, can be used in the inversion process (340). If the marker apparatus (102) communicates the orientation of the magnetometer (106) via the uplink information, the mathematical model is informed of the orientation in space, thus reducing unconstrained variables when using the mathematical model in the inversion process (340).

[0228] The localization process (338) includes numerically estimating (e g., using the iterative process) the orientation of the magnetometer (106), including in three orthogonal dimensions (3D orientation), and estimating an orientation of the marker apparatus (102) from the numerically estimated orientation of the magnetometer (106).

[0229] The inversion process (340) includes using the measured orientation of the magnetometer (106) with the mathematical model when numerically estimating the location of the magnetometer (106) which may improve the efficiency / precision of the inversion process (340).

[0230] The mathematical model associates the magnetic field measurements, the determined source locations in 3D, and the 3D location of the magnetometer (106). The mathematical model may optionally assume that the medium (104) is homogeneous, and / or that the medium (104) has a skin depth substantially approaching infinity for frequencies at which the magnetic field (b) is modulated.

[0231] The record mobile magnetometer orientation process (336) includes determining (e g., measuring) two or more orientations of the magnetic field source (105) at the two or more source locations in three orthogonal dimensions (3D orientation) (thus determining the orientations of the magnetic field source (105) when the magnetic field measurements are / were determined. The localization process (338) may take into account the orientations of the magnetic field source (105) when estimating the location of the magnetometer (106).

[0232] In the record mobile source orientation process (336), determining of the two or more orientations of the magnetic field source (105) may include: a. determining (e g., measuring) orientation of the mobile platform (108);b. determining (e g., measuring) relative orientation of the magnetic field source (105) to the mobile platform (108), which may be rigidly fixed and set at the factory; and c. estimating the two or more orientations of the magnetic field source (105) based on a numerical addition / subtraction of the orientation of the mobile platform (108) and the relative orientation.(0233] The localization process (338) includes receiving the two or more orientations of the magnetic field source (105) from the record mobile source orientation process (336).

[0234] The 3D locations may include three Cartesian values or three spherical values.

[0235] The mathematical model may include: a. a closed-form mathematical model with a system of closed-form equations (mathematical relationships); or b. a numerical integration model (e.g., a finite element analysis (FEA) model).

[0236] The closed-form equations represent solutions to Maxwell's equations for a magnetic dipole in a conducting / permeable medium with a simple structure. The numerical integration model represents integration of Maxwell's equations for the magnetic dipole (e.g., an infinitesimal magnetic dipole) in a conducting / permeable medium with any structure. In some applications, the closed-form mathematical model may be preferable for being faster. In other applications, the FEA model may be preferable for being more accurate. For embodiments using the FEA model, the cost function includes: {modelled value} minus {measured value}, where each {value} can be total field, coherent vector or magnitude vector.

[0237] The process (300) allows the magnetometer (106) in the marker apparatus (102) to have any orientation (i.e., an arbitrary orientation, e.g., caused by movement of the medium portion) while still being accurately localizable, thus addressing problems of expensive / unreliable internal self-righting mechanisms in previous buried markers. Themarker apparatus (102) remains stationery during the two or more measurements (e.g., by being buried), with a fixed location and orientation, with respect to the duration of the two or more measurements Using the magnetic field source (105) attached to the mobile platform (108) may be more flexible / efficient that just using an array of sources fixed in space, e.g., at fixed stations relative to a mining site.

[0238] Use of the mathematical model allows localization of the marker apparatus (102) without requiring detection of a signal maximum from the magnetic field source (105) on the surface or in space, thus without requiring the mobile platform (108) to pass through a region of space creating the signal maximum at the marker (102). This may allow for efficient / flexible routing of the mobile platform (108) around a site with one or more of the marker apparatuses (102). The mathematical model includes relationships between the 3D marker location and field measurements and the magnetic field source locations, thus allowing a "one-step solution" of the 3D marker location, rather than estimation of an XY location from a maximum signal and a separate estimation of a Z (depth) location from knowledge of ground permeability, e.g., as required with previous markers.

[0239] Use of the mathematical model allows localization of the marker apparatus (102) in three orthogonal dimensions (3D location) without necessarily requiring knowledge of the marker sensitivity calibration or marker orientation and may avoid the need for factory calibration of the sensitivity (K) (in the calibration process (303)) and / or alignment of the magnetometer (106) with respect to a shell (714) of the marker apparatus (102).

[0240] The mathematical model may be based on the infinitesimal dipole model because the distance between the marker apparatus (102) and the magnetometer (106) is generally substantially larger than the radius of the magnetic field source (105).

[0241] The navigation module (118) and / or the remote location tracking system may be configured to measure a P&O history of the magnetic field source (105), and thus to measure the source’s position and orientation (P&O) at each measurement location.

[0242] As described hereinafter, the navigation module (118) may include:a. the global navigation satellite system (GNSS) receiver for above-ground / water applications; b. an inertial navigation system (INS); c. a simultaneous localization and mapping (SLAM) system, e.g., when GNSS is denied, e g , the LiDAR SLAM system; and / or d. a receiver in an underwater acoustic positioning system.

[0243] The GNSS receiver is preferably mounted on top of, or not below, the mobile platform to mitigate the mobile platform shadowing the satellites.

[0244] The INS may be configured to operate with the GNSS receiver to measure the source position and orientation (P&O) at each measurement location. Alternatively, the INS may be configured to operate independently of, or without, the GNSS to measure the source P&O at each measurement location. The GNSS-INS system includes a GNSS (GPS and other satellite services, potentially using multiple GNSS constellations at the same time) measurement system onboard, may include corrections data from a reference station, and may include measurements from an onboard IMU (accelerations) and compass (geomagnetic direction). The GNSS-INS system includes sensor fusion algorithms to calculate the P&O over time, either in real time (e.g., using a Realtime Kinematics, RTK, system) or after the measurements have been made (e.g., using a Post-Processed Kinematics, PPK, system).

[0245] The tracking module may be configured to measure the P&O of the mobile platform (108), and the system (100) is then configured to determine the source P&O from the mobile platform's P&O. The navigation module (118) may include a commercially available dualantenna heading GNSS-INS sensor unit, and / or PPK software, additionally / altematively, the P&O system may include / incorporate a pose estimation system of a movement / flight controller of the mobile platform (108) (e.g., drone) — for example, the mobile platform (108) may include a flight controller configured to generate the P&O measurements, and the flight controller may be coupled / connected to the system to receive the P&O measurements from the mobile platform (108).

[0246] The system (100) may determine the source orientation (which may be referred to as the "payload orientation") from the mobile platform's orientation (which may be the drone’s airframe orientation) by measuring a relative orientation between the magnetic field source (105) and the mobile platform (108) by way of the relative pose measurement system described hereinbefore. Or it may be rigidly fixed, with known relative orientation. The tow member allows for the suspended payload to be used where it makes a significant difference to separate the mobile platform (108) and the magnetic field source (105) or the wireless Ml receiver component (117), or when the mobile platform (108) is a boat.

[0247] Using the relative pose measurement system in addition to the navigation module (118) may be desirable since attaching the navigation module (118) directly to the magnetic field source (105) or the wireless MI receiver component (117) may be undesirable because: the navigation module (1 18) might be preferably installed on top of the mobile platform (108) as described hereinbefore so GNSS signals are not blocked by the mobile platform itself, and the magnetic field source (105) or the wireless Ml receiver component (117) might be preferably installed underneath the mobile platform so the source may be positioned closer to the marker apparatus (102) during the operation (movement of the source between the measurement locations) by gravity.

[0248] As described further hereinafter, the magnetic field source (105) or the wireless MI receiver component (117) may be connected beneath the mobile platform (108) by a gimbal. The relative pose measurement system may include two or more rotary encoders (119) configured to measure two gimbal angles continuously / repeatedly or at least at each source location: e.g., two encoders (11 ) for two gimbal angles (if the gimbal is constructed to not allow movement in one orientation, e.g., yaw), or three encoders (11 ) for three gimbal angles. The at least one digital processor may be configured to combine the position, and optionally orientation, of the mobile platform (108) with the two gimbal angles to calculate the P&O of the magnetic field source (105) or the wireless MI receiver component (1 17) over time (continuously / repeatedly, including for each source location). When the system (100) includes the one or more mechanical linkages (202), and these are substantially rigid (e.g., the pole), the system (100) is configured to estimate / measure / determine the source position and orientation using a vector sum of the P&O of the mobile platform (108), the selected distancebetween the magnetic field source (105) or the wireless MI receiver component (117) and the navigation module (118) (due to the mechanical linkages (202) and the mobile platform's frame), and the measured angle from the encoders (119).

[0249] The relative pose measurement system may include an on-board wireless localization system configured to provide measurements in up to six degrees of freedom (DoF) using axial rotation measurements of the magnetic field source (105) or the wireless MI receiver component (117) relative to the mobile platform (108), for example including: at least one 3D transducer / target on one of the mobile platform (108) and the magnetic field source (105) or the wireless MI receiver component (117), and at least one 3D wireless sensor on the other of the mobile platform (108) and the magnetic field source (105) or the wireless MI receiver component (117), wherein the 3D wireless sensor generates the relative orientation for each source location. The on-board wireless localization system may include a 6 DoF magnetic induction system, Alternatively / additionally, the on-board wireless localization system may include a camera / image sensor as the wireless sensor and a visible target on the magnetic field source (105) or the wireless MI receiver component (117), e.g., based on a fiducial marker on top of the magnetic field source (105) or the wireless MI receiver component (117) (visible to camera / image sensor) and visual tracking of the fiducial marker from the camera / image sensor on the mobile platform (108).Path generation process (306)

[0250] As shown in FIG. 4, generating the intended path (124) includes the planning system: a. generating coordinates of a search area (which are generally horizontal coordinates) selected to bring the magnetic field source (105) within the magnetic field detection range of the one or more marker apparatuses (102) (the search area may be defined by a bench or a muckpile using latitude / longitude values and / or local coordinates in process (420)); b. optionally generating the coordinates based on data exported from blast design software (402) (e g , SHOTPlus);c. optionally generating the coordinates based on a region of interest manually selected by mine geologists (404); d. for an airborne platform, in process (406), optionally calculating an altitude for the mobile platform (108) (thus vertical coordinates), which may include automatically selecting vertical coordinates that are a selected distance above the boundary between the media (which may be generated from topographic information of the search area), and / or receiving user input (e.g., of a pilot’s judgement and choice of take-off location) in process (408) — altematively / additionally, using a pre-defined height above the boundary (e.g., selected to be equal to or less than the magnetic field detection range) and an active terrain-following mechanism of the mobile platform (e.g., wheels, or a altimeter) in process (416); e. automatically generating a boundary polygon for movement of the mobile platform in the search area using geometrical operations on the horizontal and vertical coordinates in process (410); and f. automatically generating the intended path (124) for the mobile platform within the boundary polygon in process (412), which may include using at least one predefined patterns, e.g., a zigzag or square-wave pattern in processes (414,416) — or alternatively receiving user input during the movement to control the intended path (e.g., from the pilot) in process (418).

[0251] The intended path (124) need not be followed accurately because the source locations are measured simultaneously / contemporaneously with the magnetic field measurements in the markers, and the measured locations are used in the inversion (not the intended path coordinates). Any path in 3D space may be used, as long as it is measured accurately, and as long as it spans / covers the area of interest with coverage sufficient to reliably wake and transmit the localisation signal to all of the markers to be used, e g , selected by a user / operator of the system (100) depending on the application (e.g., where the muckpile will be). The system (100) may include a user interface that displays the flight boundary and the detected marker locations (to the user) so the user can see if any located markers are close toor outside the selected boundary, and the user interface may be configured to prompt the user to re-fly the mission with an adjusted boundary (such that it is within the magnetic field detection range), to get better results.

[0252] The system (100) determines global position, global orientation of the magnetic field source (105) and magnetic field amplitude (and optionally phase) at the marker for each source location (or 'station') used in the inversion. The global position and global orientation of the magnetic field source (105) may be comprised of global P&O of the mobile platform (108) plus the relative P&O of the magnetic field source (105) relative to the mobile platform (108). The global position and global orientation values may be measured directly or estimated. For example, if the magnetic field source (105) has a consistent orientation without significant wobble, the global orientation values may be substantially consistent for a plurality of the measurement locations / stations, so the global orientation values (pitch, yaw, roll) may be estimated for the plurality of the source locations / stations, e.g., based on orientation values estimated / selected during design of the system (100) (e.g., by setting the global orientation of the magnetic field source (105) relative to the ground by affixing it to the mobile platform (108) at a fixed orientation and driving / flying / moving the mobile platform (108) only in substantially straight lines): this may reduce the measurement time required at each source location.Data Reduction Process (500)

[0253] As shown in FIG. 5, correcting the P&O measurements and initiating the inversion includes: a. in step (502), receiving the data from the marker DAQ component (114) and the mobile DAQ (121) / stationary DAQ, including from: i. in substep (503 A), measuring the relative P&O (e g., relative to airframe) of the magnetic field source (105) and the mobile platform (108) using the relative P&O system (e.g., including the encoders (H 9)),ii. in substep (503B), receiving the magnetic field measurements from the marker apparatuses (102), and iii in substep (503C), optionally receiving the navigation data from the tracking module; b. in step (504) receiving the corrections data, e g., for the GNSS; c. in step (506), performing the kinematics processing using the corrections data and the navigation data; d. in step (508), determining the actual P&O of the mobile platform (108), e. in step (510), determining the actual P&O of the magnetic field source (105) from the actual P&O of the mobile platform (108) and the relative P&O using the vector addition; f. in step (514), separating the different source signals using the selected multiplexing process(es) described hereinbefore; g. in step (516), extracting the magnetic flux density for each source location and each marker apparatus (102); h. matching corresponding source position and signal measurement data (e g. based on the time stamps); and i. in step (518), providing the corrected data to the inversion process (340).Inversion Process (340)

[0254] As shown in FIG. 6, performing the inversion process (340) includes: a. in step (602), optionally receiving approximate marker locations or search regions to initiate the estimation processes;b. in step (606), optionally providing an approximate P&O from step (602 for use as a starting guess for the solver; c. in step (608), receiving a position and orientation history of the magnetic field sources (105), during this mission, d. in step (609), optionally receiving the (partial) orientation data for the magnetometers (106) / markers (102), e. in step (610), receiving a signal history of the magnetometer (106) on the markers (102), during this mission; f. in step (612), looping or iterating on the P&O of the marker to minimise the cost function, including: i. in step (614), calculating the cost function, and ii. in step (616), generating new guesses for the marker's P&O; and g. in step (618), providing the solution for the marker's P&O, and thus the location of the magnetometer (106) on / in the marker apparatus (102)

[0255] Performing the inversion process (340) may include providing additional starting guesses, looping or iterating to provide an iterative solution for each, and selecting the iterative solution that has the lowest 'cost' for determining the marker location.

[0256] The position and orientation history of the magnetic field sources, received in step (608) includes the source locations (in the relevant frame of reference) matched with the respective magnetic field measurements (from when the magnetic field source (105) was at those source locations). As described hereinbefore, the pairing of the source locations with the respective magnetic field measurements can occur by matching the corresponding source positions and signal measurement data in the data reduction process (500) The system (100) may record the source locations and the magnetic field measurements together, e.g., in the mobile DAQ (121) and / or the stationary DAQ, thus sequentially matching them as they are recorded (in "real time") when the magnetic field (b) measurement values are transmittedback to the source (e.g., to the mobile DAQ (121) via the uplink channel) before the magnetic field source (105) moves substantially from the source location, thus "immediately", which may be used when the uplink channel is sufficiently clear to allow for simultaneous use with the magnetic field source (105) — e.g. by duplexing and being within range as described hereinbefore. Alternatively or additionally, the pairing of the source locations with the magnetic field measurements can use identifiers (IDs) recorded in association with either the source locations or the magnetic field measurements: these IDs may be times, e.g., the time stamps described hereinbefore, and / or codes, e.g., the sequence / location codes described hereinbefore (received and recorded in the markers (102) during the measurements of the magnetic fields (b)), or record IDs associated with the magnetic field measurements (received and recorded by the sources, e.g., the mobile DAQ (121), via the uplink channel during the measurements of the magnetic fields (b)). When the system (100) uses the time stamps for the matching, the time stamps are recorded at the source (with the source locations) and at the marker (102) (with the magnetometer measurements), matched later. Using the time stamps does not require the sequence / location information to be sent alongside the magnetic fields (b) as described hereinbefore, and allows the source locations and the magnetic field measurements to be matched / paired at a later time and remotely from the mobile DAQ (121) / stationary DAQ and the marker DAQ (114) — this matching / pairing at a later time can include shortly after the measuring but during the mission (e.g., if the source locations and the magnetic field measurements are sent in substantially "real time" to the data receiver component (122) and matched / paired in the microprocessor (110)) or after a longer time, e.g., after the mission is finished, in post processing (e g., if the source locations and the magnetic field measurements are recovered after the mission from data stored by the mobile DAQ (121) / stationary DAQ and the marker DAQ (1 14) respectively, including by parking the mobile platform (108) to recover the data from the mobile DAQ (121); however, using the time stamps does require the source and marker clocks to be aligned (e.g., the clocks in the mobile DAQ (121) and the marker DAQ (114) respectively), which can happen once (e.g., before, during or after the magnetic fields (b) are sent / measured), or more, e.g., when there are two or more clock synchronization messages for these source and marker clocks. When the system (100) does not rely on just the time stamps, because the magnetic field source (105) can drift in and out of range, it is not sufficient to simply use lists of the sourcelocations and the magnetic field (b) measurements to be matched up later: instead, the IDs include some position information with each magnetic field (b) signal, and this position information (or "downlink source location information") can include explicit latitude / longitude information, explicit map grid coordinates, and / or compressed coordinates (e g., a local delta x, delta y and delta z). When the system uses the records IDs, the or each marker (102) that is measuring one of the magnetic fields (b) sends the or each record ID to the relevant source via the uplink channel, e g., to the wireless Ml receiver component (117) and / or via the wireless MI multihop signal (130), while the mobile / stationary platform (108,126) is at / in the source location, and the mobile DAQ (121) or an equivalent data acquisition component that is separate / remote from the marker apparatus (102) and on / in the stationary platform (126) (referred to herein as a "stationary DAQ") records / include the record ID when recording the source location, such that the system (100), in the matching / pairing process described, knows which marker measurement pairs with which source location.

[0257] The at least one predefined mathematical model (between the model magnetic dipole at the plurality of source locations and the modelled magnetic field strengths / directions at the plurality of modelled measurement locations (marker locations)) may itself be referred to as the "forward model", and it may include or represent the following relationship for each pair of the magnetic field source (105) and the magnetometer (106) as the magnetic field is being measured (each source and sensor pair):where K includes the set of magnetometer calibration values, in is the unit vector in the direction of the magnetic moment (in the source frame), Am is a rotation matrix describing the orientation of the source reference frame relative to the global reference frame, P the tracking matrix (a rotation matrix), as described in Kuipers JB, others (1999) "Quaternions and rotation sequences: a primer with applications to orbits, aerospace, and virtual reality". Princeton University Press, Princeton — this describes the direction between the station and the marker), C the coupling matrix (the ‘shape’ of the magnetic dipole field), m the magneticmoment (magnitude), uathe vacuum permeability, r the distance between station and marker, and the rest as described hereinbefore.

[0258] The mathematical model can thus use both source orientation (the orientations of the magnetic field source(s) (105) at the source locations) and the magnetic sensor magnetometer orientation (the orientation of the magnetometer (106) at the sensor location) as inputs. For example, if the marker apparatus (102) contains the "IMU" accelerometer (818) and the "compass" magnetometer (820), then the magnetometer orientation can be used; whereas, if the marker apparatus (102) contains the "IMU" accelerometer (818) and not the "compass" magnetometer (820), only partial orientation information for the magnetometer (106) is available as an input for use in the mathematical model.

[0259] As the plurality of the measurements of the magnetic field (b) in the marker apparatus (102) are made corresponding to the plurality of source locations, the at least one digital processor estimates the marker location and optionally orientation by performing an inversion of the forward model to fit the plurality of measurements. Thus the determination / calculation of the marker location is based on: the plurality of measurements of the magnetic field (b) at the marker apparatus (102); the plurality of respective recorded source locations and orientations, optionally (partial) marker orientation information, and the at least one predefined mathematical relationship. This estimation of the marker (field measurement) location may be referred to as "inversion of the forward model", "solving the inverse problem", and / or as "fitting" the forward model to the measurements.

[0260] The inversion process (340) may include an iterative process to minimise the cost function (also referred to as an "objective function"), and various appropriate cost functions are described hereinafter, and in the Appendices, applicable in different situations / applications, e.g., depending on available SNR, the required accuracy of the marker locations, and / or the processing power of the at least one digital processor. Alternative cost functions and minimization processes may be used as a person of ordinary skill in the relevant art would comprehend.

[0261] If the orientation of the marker in the global reference frame is known, e g., if the marker apparatus (102) is a self-righting marker such that its magnetometer orientation isalways fixed, e.g., having a single axis magnetometer always vertical, and its sensitivity (K) is calibrated, the marker apparatus (102) effectively has 3 degrees of freedom (DoF), e.g., X, Y and Z directions, in the reference frame.

[0262] If the orientation of the marker in the reference frame is not known, e.g., if the marker apparatus (102) is not configured to be self-righting and the orientation of the magnetometer (106) is not known, the marker effectively has 5 degrees of freedom (DoF), e g., X, Y and Z directions, and heading and elevation orientations in the reference frame. Using the definitions of Kuipers JB, the two orientation degrees of freedom for the single-axis marker may be referred to as: (i) heading (wherein yaw is a change in heading), and (ii) elevation (wherein pitch is a change in elevation); and the symmetry axis (which is the missing degree of freedom for a single-axis marker) may be referred to as bank (wherein roll is a change in bank).

[0263] The numerically estimating of the marker location in the three orthogonal dimensions (3D) using the mathematical model requires a different minimum number of the two or more magnetic field measurements (and the two or more source locations) depending on the DoF of the magnetic field sensor / magnetometer (106) in the marker (102), in other words the number of unknown degrees of freedom of the marker (102), which can include sensitivity calibration and orientation (of the sensor / magnetometer (106)) and magnetometer location in 3D, thus up to 6 unknowns (in the preferred implementation, the marker (102) contains a single-axis magnetometer which is symmetrical about its axis, so there are not 7 unknowns). Alternatively, there could be more than 6 unknowns if the magnetometer sensitivity (K) has one or more unknown values, including sensitivity in 1 to 3 orthogonal directions: e.g., the magnetometer (106) having only a single pickup coil can be described / defined by a scalar sensitivity, a three-axis magnetometer can have a 3x3 calibration matrix (with 9 parameters / unknowns), and — furthermore — each element of the calibration could have a phase shift which could be considered an additional parameter, although treating up to 9, or up to 18, calibration parameters as unknowns may be over-fitting and not preferred. The minimum number of the two or more magnetic field measurements also depends on the type of the magnetometer (106) and thus whether the magnetic field measurements are scalar,vector or phasor, and how many dimensions each measurement has (from 1 to 3 orthogonal dimensions). For example: a. for the total scalar magnetometer, the minimum number of the two or more magnetic field measurements (corresponding to substantially non-overlapping source locations) can be equal to the number of unknowns in the Total Field Inversion Process, e.g., 5, or 4 (if the magnetometer sensitivity (K), or "sensor calibration", is known) since the total field magnetometer is independent of orientation (thus the marker orientation cannot be measured by the system (100)); and b. for the vector magnetometer (without phase information), and for the coherent vector magnetometer, which can make 1, 2 or 3 independent measurements for each source location, the minimum number of measurements can be equal to the number of unknowns, but the number of locations can be fewer by a factor of the number of independent measurements for each location.

[0264] The magnetic field (b) is a vector quantity, meaning that it has a direction in space. This can be described using three vector components in x,y, z directions Since the modulated magnetic field (b) is an alternating field, it also has a phase. The three vector components may have a phase shift relative to each other, and also relative to the source magnetic dipole. In embodiments, the magnetometer (106) may be configured to sense the three vector components, and optionally their phase (the "coherent vector magnetometer"), or it may be sensitive only to the magnitude of the field (the "length" of the total field vector, or the "total field", thus a "scalar magnetometer"). A vector magnetometer measures the magnetic flux density in the magnetometer frame, bsTotal Scalar Magnetometer - Total Field Inversion Process

[0265] A total field magnetometer measures ||s||. The total field can be calculated from the vector field where || ■ || indicates the Euclidean norm or 2-norm.

[0266] The total root-mean-square (RMS) flux density squared for a single-coil source is given by:using the forward model, wherein the coupling matrix C can be a constant for the free-space model, and the asterisk in b* indicates the complex conjugate transpose.

[0267] In the inversion process (340), the coherent vector inversion includes the process of Appendix C.

[0268] Tn the inversion process (340), a cost function for the inversion is determined as a difference between the measured total field and the predicted field (for each measurement corresponding to each source location), and the Total Field Inversion Process includes a nonlinear optimisation process (performed by the microprocessor (110)) to find a solution for marker position:where m is in the source frame, and the source moment (m) and the magnetometer sensitivity (K) are assumed calibrated, so we have 3 Degrees of FreedomNon-Coherent Vector Magnetometer - Absolute Value Inversion Process

[0269] In the inversion process (340), the Absolute Value Inversion Process includes the process of Appendix D. This is used when the phase information is not available. Only the magnitude part of the phasor is used The measurement and forward model prediction are still vectors, but now they are just vectors of magnitudes.

[0270] Rather than using only scalar value (the total field) as described hereinbefore, the processor may use the magnitude of each vector component individually. The quantity |bs| is the vector containing the three x, y, z direction magnitudes individually as its elements.The absolute value of each component is thus measured, but the phase / quadrant is not measured (thus the sign of the amplitude or equivalently the phase is unknown). A measurement of the signal phase (or equivalently the ‘sign’ of the signal amplitude) is not required:The solution has 5DoF for a single axis magnetometer in the receiver (magnetometer (106)), and 6D0F for a 2- or 3-axis magnetometer (106). The absolute value inversion process uses more information than the total field inversion process (by using the length of each component rather than just the vector’s total length), so can give better localization performance.

[0271] The absolute value inversion process may be suitable for systems with vector magnetometers and non-coherent detection, or systems with vector magnetometers and coherent detection, where some / all of the measurements have high uncertainty in the measured phase (‘sign’ of the amplitude), which can happen when SNR is low. When magnitude can be measured more precisely than phase, it may be preferable to reject the phase information.Coherent vector magnetometer - Coherent Vector Inversion Process

[0272] In the inversion process (340), the coherent vector inversion includes the process of Appendix A. The magnetometer measurement provides the coherent vector of measurements b this is a three component vector (x / y / z) where each component is a phasor. The process may round the phase to the nearest 0 or pi. The process may subtract the predicted value of b from the forward model to provide a cost function to optimise.

[0273] The magnetic flux density b is measured by the magnetometer. It is a time-varying vector. Each component is sinusoidal. In general, b will have elliptical polarisation due the effect of the ground and other phase shifts in the system. Close to the marker, or in ideal free space, the polarisation is simpler and can have values of 0° or 180°. This is equivalent to the components having positive amplitude or negative amplitude. The phase can provideadditional information which can be used in the inversion. The simplest cost function may be just the forward model thus:

[0274] In general the cost is complex-valued so the cost will have a contribution from a real part and an imaginary part; or a magnitude and a phase angle (both set equal to zero). Thus, there will be two cost functions for each source location (or "station") that are optimised together. Generally, the phase angle will have higher uncertainty so it may be given a lower weighting than the magnitude as described hereinafter.

[0275] In a version of the coherent vector inversion process, the phase may be measured / determined to the nearest 0° or 180° (which is the same as measuring the sign of each (now real-valued) component of bs\ in which case the coupling matrix has the simple form for a dipole in free space. This may be of assistance when fitting the measurement to the cost function above because assuming that the phase is 0 or 180 simplifies this function: C is given by [2 0 0;0 -1 0; 0 0 -1], This eliminates a variable from the cost function (the skin depth, which will usually be an unknown). If the cost function is solved for a general phase angle, the form of C is much more complicated.Phase Recovery for the Coherent Vector Inversion Process

[0276] As the marker apparatus (102) and the magnetic field source (105) have different clocks that are generally not synchronised, they are “non-coherent”, so phase recovery is necessary for the coherent vector inversion process (340), performed by the at least one microprocessor (110).

[0277] The phase recovery process may include decision directed carrier recovery, which includes matching the signal to a known digital code, which indicates the start of the packet (indicating ‘where to start measuring the phase’), e.g., as described in lohnson CR & Sethares WA (2004) “Telecommunication Breakdown; Concepts of Communication Transmitted via Software-Defined Radio”, Pearson-Prentice Hall.

[0278] The phase recovery process may include measuring a reference tone including a second sinusoid in a reference magnetic signal, including at a different frequency from the carrier frequency (fc), generated by the magnetic field source (105) and detected by the marker’s magnetometer (106). The two tones are selected to be factors of a common higher frequency so they will periodically align, and this can be taken as the phase reference. At longer distances between the marker apparatus (102) and the magnetic field source (105), phase measurement becomes uncertain and non-coherent processes (including the total field or vector absolute value processes) may give better P&O measurement precision.

[0279] This coherent measurement enables the coherent vector inversion processes.Applications / Examples

[0280] Monitoring operati on s / appli cations, such as in the examples listed below, may benefit from: a. not needing to ‘survey -in’ the devices (P&O) during deployment, or at least not needing to do so relative to the expected marker locations; b. wireless / tetherless deployment; and / or c. wireless communications.

[0281] Examples of the system (100) and process (300) may be used for localizing markers in one or more of the following operations / application fields: a. block caving: caved extent, movement of caved material; b. geotechnical monitoring (measuring pore pressure, inclination changes etc.) for slope stability, tailings dams, water reservoirs, leach heaps stability (at mines), and / or stockpile stability; c. checking wireless primer locations for commercial blasting applications, surface, underground (U / G), seismic, civil, including ensuring the wirelessprimers are in safe locations, not moved, including checking for slumping / floating / missing primers; d. encoding wireless primers (with their delay times) in the rock according to detected position and a blast design; e. coal stockpile and landfdl temperature and temperature gradient monitoring (for spontaneous combustion), f. in surface mining, measurement of borehole toe position and water level depending on the density of the marker apparatus (102), g. in underground mining, wherein the as-drilled borehole location in underground mining to be used when designing a shot with continuous density control when loading emulsion explosives (e g., Orica's "4D"); h. marking underground utilities, especially long ones with many markers, e.g., pipelines, including with markers configured for leak detection; i. monitoring explosives in hot and / or reactive ground; j. tracking ore / waste to stockpiles, conveyors, dumps, crushers, e.g., similar to Orica's ORETrack; k. locating snow (avalanche) monitoring sensors to measure snow thickness, stresses inclination changes etc.; l. detecting or tracking drill bits, or portions of drill bits or drill strings, used to drill rock / boreholes, including during drilling and / or if portions break off, i.e., become detached in the ground / rock; m. measuring draw within coarse ore stockpiles (internal movement trajectories) for the purposes of tracking grade / hardness / fragmentation information within the stockpile, e.g., when material is added on the top from the crusher and drawn out from beneath;n. tracking locations of objects during demolition blasting by securing / attaching the marker apparatus (102) thereto, e.g., metals intended for recycling, or hazardous objects that cannot be removed from the structure prior to blasting; and o. near-surface soil monitoring for agriculture, e g., using devices configured to monitor moisture etc. in the soil, e.g., devices including the marker apparatus (102) that are tolerant to ploughing, and detecting their positions while wirelessly gathering the sensed soil monitoring data.

[0282] In ore tracking operations, as described hereinbefore, the system (100) may include the marker apparatuses (102) buried adjacent to or in an ore body (e g , down a borehole), and the process (300) may include tracking the ore body during blasting, excavation and / or processing by the localization of the corresponding marker apparatuses (102) The process (300) may include measuring draw of a stockpile by repeated localization of the corresponding marker apparatuses (102) over a selected time period.

[0283] In commercial blasting operations, as described hereinbefore, the system (100) may include at least one marker apparatus (102) that includes or forms a blast initiation device or blast primer device for initiating blasts, and the process (300) may include localizing the blast initiation device or the blast primer device based on the localization of at least one marker apparatus (102) that includes or forms the blast initiation device or the blast primer device.

[0284] In drilling operations, the system (100) may include at least one marker apparatus(102) substantially adjacent to, coupled to or incorporated into a drill bit or a drill string. The process (300) may include localizing at least a portion of the drill bit or drill string by localizing the corresponding marker apparatus (102) during drilling with the drill bit or drill string (e.g., in the opaque medium (104)), or after detachment of the portion from the drill bit or drill string (e.g., in a muck pile). The detecting or tracking of the drill bits may including detecting tracking "drill steel", including drill bits lost in the rock / earth during drilling of boreholes. The process may include loading a borehole with both the marker apparatus (102) and the drill steel, including loading the marker apparatus (102) into the borehole that contains a portion of drill steel lost in the borehole. The process can includemarking / recording that marker apparatus (102) — the "drill marker apparatus" — as tracking or corresponding to the lost drill steel, e.g., using the marker's code or ID; alternatively, the drill bit marker may be the only marker used in the shot, so ID may not be required, to distinguish it from ore markers / primers etc. The process can then include the localization of the drill marker apparatus, and hence substantial localization of the drill steel, including before blasting, after blasting, during excavation of the muck pile, and during processing of the excavated material. Localization and monitoring / tracking of drill steel in the mine / quarry site and material processing can be critical to mitigate lost drill steel damaging processing equipment, especially in sites where the rock is hard, so the drill steel is very hard and thus harder than the material being processed. By provision and tracking of drill marker apparatus, the position of the lost drill steel is provided to survey / fleet management systems, e g., software controlling excavation, and a selected volume of the material around the lost drill location is dug out and sent to waste, or the drill steel recovered and removed in a separate processing / excavation step. More than one marker may be deployed with the drill bit, for the sake of redundancy / reliability. The bit may be bonded to the marker, e g., using resin / grout, to increase the likelihood of the bit being close to the marker after the shot. In addition to a survey / FMS system, an augmented reality system could be used by a spotter to help guide a person operating an excavator.

[0285] In seismic operations, including transition zone seismic blasting, as shown in FIG. 9, the system (100) may include the marker apparatuses (102) respectively incorporated into or attached to the seismic receivers (902) (hydrophones / geophones) and / or the seismic sources (904) (blasting devices). The process (300) may include localizing the seismic receivers (902) and / or the seismic sources (904) localizing the marker apparatuses (102) incorporated therein or attached thereto. The seismic sources (904) may include quasi-planar shock wave generators, including as described in International Patent Application W02020263194A1 (Petrovic et al., entitled "Deployment of quasi-planar shock wave generators in association with seismic exploration"), the as-published specification of which is hereby incorporated by reference herein in its entirety. As shown in FIG. 11, in a land seismic blasting application, the marker apparatuses (102) in the seismic receivers and / or sources can be buried in the medium (104) and / or resting on the surface of the medium (104). As shown in FIG. 12, in atransition zone seismic blasting application, the marker apparatuses (102) in the receivers and / or sources can be buried in the medium (104) including sand / rock / earth, and / or resting on the surface of the medium (104), and / or suspended / submerged in the medium (104) or the navigable medium (112), e.g., water — and the mobile platform (108) may be mobile in the navigable medium (112), e.g., air. The magnetic field may be generated by a vehicle (908) that includes the mobile magnetic field source (105), the mobile platform (108), the wireless Ml transmitter component (116), the navigation module (118) and the data Tx component (120). The mobile platform (108) may include a drone, submersible drone, surface boat, or submarine. The vehicle (908) is controlled to move between different measurement positions 910A, 910B (or "stations") to generate the magnetic field. As shown in FIG. 10, the path may include a first path (124A) and a second path (124B) joined by a transit path (124C): the vehicle (908) is controlled to generate the magnetic fields along the first path (124A) and along the second path (124B) where the devices are approximately located, and the vehicle (908) is controlled (optionally) to not generate while transitioning along the transit path (124C) where no devices are known to be located (thus saving energy and data storage capacity). The transit path (124C) allows for typical seismic survey arrangements where arrays of the sources and the receivers are substantially separated in space. The receivers (902) may be formed in arrays and the seismic sources (904) may be formed in arrays. The process may include measuring the actual 3D positions of the seismic sources (904) ahead of firing. The process may include measuring the 3D positions of the receivers (902) by incorporating the marker apparatus (102) into or with the receiver (902). The locations (measured by the system 100) of the seismic receivers (902) and the seismic sources (904) are used with the measured seismic vibrations in a seismic inversion process. The seismic receivers (902) and the seismic sources (904) can be synchronised to the same time base using the MI communications in the same way as wireless primer delays are synchronised, e g., in Orica's WEBGEN system, and / or as described in International Patent Application Publication No. WO2020263193A1 (Nielsen et al., entitled "Commercial Blasting Systems"), the as-published specification of which is hereby incorporated by reference herein in its entirety. These position measurements reduce the need to survey in the seismic receivers (902) and the seismic sources (904): thus approximate locations can be used during deployment, and the actual as-buried depth measured using the marker apparatus (102).These position measurements may be useful for seismic surveys in transition zones that are prone to movement: the actual positions of the seismic sources (904) and the seismic receivers (902) can be detected after movement, before firing, and the actual positions may differ substantially from the original positions (906). The position measurement processes can be performed in the same flight path as other drone-based tasks using the mobile platform (108), such as drone-based deployment (dropping) and retrieval of the wireless seismic receivers (902), drone-based deployment of the seismic sources (904), drone-based geophysics methods, especially 'electromagnetics' methods, and drone measurement of a topological / di ital elevation model of the ground surface. In some applications, the drone / mobile platform (108) can land and generate the magnetic fields (b) with the MT signal generator / magnetic field source (105) attached to the airframe.

[0286] Tn avalanche blasting operations, the process for drone-based avalanche blasting may be similar to the seismic blasting process, including using receivers with the marker apparatus (102) for detecting whether the avalanche has been successfully triggered, and including locating primers with the marker apparatus (102) where an avalanche has occurred after deployment of the primers but before their firing.

[0287] In leach mining operations, the system (100) may include the marker apparatuses (102) placed on or buried in the opaque medium (104) in the form of broken rock (e.g., in a heap). The process (300) may include: placing / burying the marker apparatus (102) in the broken rock; and subsequently monitoring movement of the broken rock by repeatedly localizing the marker apparatus (102) buried in the broken rock. The system (100) can include sensor devices or blast initiator / primer devices, each incorporating one of the marker apparatuses (102), deployed in the leach heap, and the process (300) can include localizing the sensor devices or the blast initiator / primer devices by localizing the or each corresponding marker apparatus (102). These marker apparatuses (102) need not be deployed in holes: they could be added to the rock at a prior stage of the mining process before heaping (or stacking) the heap, e.g., to an un-blasted bench, in a conveyor, in a truck, and / or to ore before processing (Run Of Mine). The process may include re-localizing these marker apparatuses (102) when the heap is "re-stacked", which includes digging and rebuilding a heap to reinvigorate flow of the lixiviant. The 3D locations of the markerapparatuses (102) (thus of the sensors / primers) may be useful for in-place recovery, "in-place leaching" (IPL), or "stope leaching", because the stope can settle when material is drawn from the bottom or over time The process (300) may include measuring the positions of marker apparatuses (102) buried under an impermeable liner beneath a leach heap, e.g., for the purpose of detecting leaks through the liner.

[0288] In dig limiting operations, the system (100) may include at least one marker apparatus (102) buried in a selected location in the opaque medium (104) relative to and / or adjacent to and / or above explosive material, generally in an explosive column with a blast initiation device or blast primer device for initiating the explosive material: the marker apparatus (102) thus marks the location of the explosive material for safety reasons. The process ( 00) may include placing the marker apparatus (102) at or near the top of the explosive column, or at least above the explosive material, e g., in the stemming. The process (300) may include localizing the explosive material in the opaque medium (104) by localizing the marker apparatus (102) buried at the selected location in the opaque medium (104) relative to and / or adjacent to and / or above the explosive material, which may be while digging / excavating a portion of the opaque medium (104), or in a survey process (e.g., using a drone) after a portion has been excavated The marker apparatus (102) may be incorporated into a blast initiator / primer device. In this application, the marker marks the actual top-of-charge position The detected 3D location of the marker can be compared to the topography of the ground surface, e.g., from drone photogrammetry, and used to ensure that there is adequate cover over the explosives after digging / excavation and prior to blasting of the marked explosive column (to mitigate the risk of wild flyrock etc.), e g., used by the shotfirer in their safety checks. The dig limiting application may be relevant where wireless blasting is used with buried shots because the shot remains buried while shots above are blasted and dug away, or a haul road operates above, and there may be uncertainty as to how much has been dug away.

[0289] In utility marking operations, the system (100) may include at least one marker apparatus (102) buried in a selected location in the opaque medium (104) relative to and / or adjacent to and / or above a linear utility (e.g., a pipeline / powerline) in the opaque medium (104). The process (300) may include placing the marker apparatus (102) in the selectedlocation, e.g., in a trench with the linear utility. The process (300) may include localizing the linear utility in the opaque medium (104) by localizing the marker apparatus (102) buried in the selected location (i.e., in the opaque medium (104) relative to and / or adjacent to and / or above the linear utility), optionally while digging / excavating a portion of the opaque medium (104) above the linear utility.

[0290] In soil monitoring operations, the marker apparatus (102) can include one or more environmental sensors configured to detect, monitor, estimate, or measure physical parameters of the surrounding portion of the opaque medium (104), and the environmental sensors may include temperature sensors and / or moisture sensor (e.g., for soil monitoring). The shell (714) may be configured by its size / resilience to be tolerant to ploughing / erosion (in a way that wired soil sensors, connected by wires to a central hub or an above-ground unit, would not be), mitigating the need to remove the marker apparatuses (102) from the soil / paddock / pasture, and allowing for the new position of the sensor to be measured if it moves due to ploughing / erosion. The process (300) may include localizing measured physical parameters of the opaque medium (104), e.g., pressure, moisture, and / or temperature, by localizing at least one marker apparatus (102) buried in the opaque medium (104) with respective environmental sensors to measure the physical parameter values, optionally while ploughing the opaque medium (104) adjacent / around the buried marker apparatus (102).

[0291] In mine rescue operations, the marker apparatuses (102) can form or be incorporated into tracking / communications beacons for trapped miners. The system may include the fixed magnetometers forming fixed nodes that are embedded in tunnel walls / roofs, e.g., provided by the mine to generate a resilient peer-to-peer wireless network in case of emergencies. The markers apparatuses (102) may be incorporated marker magnetic sensors that are incorporated in existing cap lamps / batteries, respirator / self-rescue devices, or sewn into clothing.

[0292] In avalanche rescue operations, or in civil engineering operations, the marker apparatuses (102) may be incorporated into rescue devices for mountain workers or engineering workers, e.g., attached or incorporated in clothing, modified ski passes / accesstags, and / or smartphone cases / power banks. The process (300) may include localizing a person or a piece of equipment buried in the opaque medium (104), e.g., an avalanche, a landslide, or a (collapsed) structure, by localizing at least one marker apparatus (102) attached to the person or the piece of equipment in the opaque medium (104).

[0293] Tn geological, seismological or construction monitoring operations, the process (300) may include placing / burying marker apparatus (102) on / in the opaque medium (104) (rock, earth, foundations or structures), and the process (300) may include localizing the marker apparatus (102) repeatedly over a selected time period to monitor movement of the opaque medium (104), e.g., up to months, years or decades, depending on the battery life of the marker apparatus (102).

[0294] In drone-based operations, the mobile platform (108) can include the mobile magnetic source and a wireless receiver to gather data from devices incorporating the marker apparatuses (102) allowing localization of the marker apparatuses (102) in the same flight path / travel pattern used to gather the relevant data. Furthermore, the process of generating the magnetic fields may be combined with another task performed by a drone, e.g., optical / thermal camera monitoring.Examples

[0295] Tn one or more embodiments, the navigation module (1 18) may include a LiDAR SLAM system based on Emesenf s 'Hovermap'. In one or more example embodiments, the marker apparatus 102 can include sensors, e g., one or more of the sensors described in International Patent Publication No. WO2012149277 (“Wireless detonators with state sensing, and their use”, Lownds and Piel, to Orica International Pte Ltd). In one or more embodiments, the coil (702) of the marker apparatus (102) can have a diameter of substantially 32 mm, a length of substantially 127 mm, substantially 205 turns, and a wire diameter of 0.5 mm. In one or more embodiments, the coil (702) can have an inductance of substantially 6 mH, and a DC resistance of substantially 2.8 Ohm. In one or more embodiments, the accelerometer (818) of the marker apparatus (102) can include a 3-axis MEM digital motion sensor, e.g., from STMicroelectronics. In one or more embodiments,the microcontroller (806) of the marker apparatus (102) may include a 32-bit microcontroller integrated circuit, e.g., from STMicroelectronics, e.g., with a Zephyr real-time operating system, coupled to a commercially available crystal resonator that provides a clock frequency to the microcontroller (806). In one or more embodiments, the marker apparatus 102 can include a coil antenna, bobbin, printed circuit board (PCB), batteries, an outer jacket or shell, and a composite magnetisable filler core, e.g., as described in International Patent Publication No. W02024076309 (“Electronic device”, Nielsen, Rasmussen and Zank, to Orica International Pte Ltd), e.g., when the marker apparatus 102 is in in the form of a location marker or sensor. In one or more embodiments, when included in or with a primer for explosive blasting, the marker apparatus 102 can include a booster and an initiator (e g , electronic detonator), e.g., as described in International Patent Publication No.WO2015199620 (“A wireless initiation device”, Wicks, Hummel and Boos, to Orica International Pte Ltd), or as in a commercially available WEBGEN unit from ORICA. The marker apparatus 102 may be configured to determine and use a level of received signal strength of the MI signals, including uncalibrated signals, e g., a Receive Signal Strength Indicator (RSSI), e.g., as described in International Patent Publication No. WO2014059468 (“Locating underground markers”, Appleby, Thiel, Maggs and Spathis, to Orica International Pte Ltd). The marker apparatus 102 may include an attachment point, also referred to as a tether lock or a cam lock or an attachment point, for securing the marker apparatus 102 to a tether for lowering / lifting the marker apparatus 102 into a location, e.g., into a blasthole / borehole. In embodiments, the attachment point is in the form of a cleat that is releasably connectable to an end of the marker apparatus 102. A tether, such as a rope, cord, cable, or the like, is to be secured to the cleat, and — in one example — the tether is to pass through the cleat, which then restrains the tether within the cleat by friction and / or a clamping force being applied to the tether. The specifications of the patent applications mentioned in this paragraph are hereby incorporated by reference in their entireties.MI Signals and Interpretation

[0296] "Through the earth" (TTE) includes or refers to the communication of signals in, through and / or across a set of physical media residing between the signal source and thesignal receiver or detector, e g., wherein at least one of the signal source and the signal detector is at least partially obstructed, overlaid, covered, surrounded, buried, enclosed, or encased by the set of physical media. The set of physical media can include one or more of rock, broken rock, stone, rubble, debris, gravel, cement, concrete, stemming material, soil, dirt, sand, clay, mud, sediment, snow, ice, one or more hydrocarbon fuel reservoirs, site infrastructure, building / construction materials, and / or other media or materials. The physical media can be referred to as "the earth", where "earth" includes the ground, soil, a rock formation, rock, construction material / concrete, stone, borehole stemming, ice, frozen ground, etc. The marker apparatuses (102) may be surrounded / buried in boreholes in hard material, or in piles of loose material: in the loose material, there may be fewer size constraints on the marker apparatus (102), so the shell (714) and the marker antenna could be long, perhaps one metre or more If marker survivability is not required, e g. for a seismic primer in a borehole, the shell (714) and the marker antenna could also potentially be one metre or more.

[0297] For the MI downlink signals, the marker apparatus (102) may be located within a near-field region or zone of the magnetic field generated by the wireless MI transmitter component (116), wherein magnetic field strength as a function of distance away from the vehicle-based or broadcast MI signal source decays, including in accordance with an inverse distance cubed relationship, and the marker apparatus (102) detects changes in near-field magnetic flux generated by the wireless MI transmitter component (116) rather than detecting far-field or radiatively propagated electromagnetic waves (e g., radio waves) generated by the wireless MI transmitter component (116). Alternatively / additionally, the marker apparatus (102) may be located within the transition region or zone (between the near-field and the far-field) of the magnetic field generated by the wireless MI transmitter component (116).

[0298] For detecting the modulated magnetic field (b) and the MI downlink signals, the magnetometer (106) may be positioned, during operation, in or beyond the near-field region or zone of magnetic field source (105), e.g., within approximately one-half of a wavelength away from the magnetic field source (105), and more commonly or particularly resides within approximately 10 skin depths (e g., less than 10 skin depths), approximately 6 to 8 skindepths (e.g., less than 8 skin depths), approximately 3 to 5 skin depths (e.g., less than 5 skin depths), or approximately 2 to 4 skin depths (e.g., less than 4 skin depths) away from the magnetic field source (105). Additionally / altematively, the magnetometer (106) may be positioned, during operation, at any distance from the magnetic field source (105) while the signal-to-noise ratio (SNR) detected by the magnetometer (106) / recorded by the DAQ component (114) is above a selected threshold (minimum SNR threshold or minimum magnetic field threshold), e.g., a selected threshold for amplitude / phase / frequency recovery. Additionally / altematively, the process (300) may include making the plurality of magnetic field measurements with varying SNRs or field strengths, and only selecting ones of the magnetic field measurements (also referred to as selecting the "stations") having SNRs or field strengths over the selected threshold for the numerically estimating of the source location The selected threshold (minimum magnetic field threshold) may be equivalent to for example 1 pi co Tesla RMS.|0299| The modulated magnetic fields (b) may travel an distance TTE that is defined by the magnetic field detection range of the magnetometer (106) and external noise (including atmospheric and man-made noise) that defines the SNR. The distance can be less than 200 meters ("m"); less than 100 m; less than 80 m; less than 60 m; between 0.10 m and 60 m; between 0.25 m and 50 m, between 0.50 m and 40 m; or between 1 and 30 m. The carrier frequency (fc) can include at least one frequency in the low frequency (LF) ITU frequency band, and / or frequencies between 100 Hz to 1 MHz, or between 0.1 kHz and 200 kHz, between 1 kHz and 10 kHz, between 1 kHz and 1 MHz, or between 5 kHz and 10 kHz, or between 10 kHz and 50 kHz, between 10 kHz and 300 kHz, or between 20 kHz and 200 kHz, or between 35 kHz and 130 kHz, or between 50 kHz and 100 kHz, or between 100 kHz and 200 kHz, or between 120 kHz and 130 kHz.

[0300] In some embodiments, the marker apparatus (102) may receive downlink signals from a large antenna (e.g., a WEBGEN antenna), including MI broadcast signals, as well as downlink signals from the wireless MI transmitter component (116). These downlink signals can travel a downlink distance (including TTE) using one or more downlink Ml signal frequencies, which can include broadcast MI signal frequencies. The broadcast MI signal frequencies, e g., from a large WEBGEN antenna, can include substantially 1.8 kHz, orbetween 1 kHz and 2 kHz, or between 100 Hz and 10 kHz, or between 0.1 kHz and 200 kHz, or between 1 kHz and 10 kHz, or between 10 kHz and 50 kHz, or between 50 kHz and 100 kHz, or between 100 Hz and 100 kHz, or between 100 kHz and 200 kHz, or between 120 kHz and 130 kHz, and the downlink distance can be greater than 100 meters; greater than multiple or many hundreds of meters; between 200 and 900 meters; greater than a kilometre; or greater than multiple kilometres. The broadcast downlink MI signal frequencies can include at least one frequency within the ultra low frequency (ULF) band, or within the very low frequency (VLF) band as defined by the International Telecommunications Union (ITU). The MI downlink signals from the wireless MI transmitter component (116) would typically be of lower power than from a large WEBGEN antenna, and would have less range, as described hereinbefore under the heading 'Downlink Signals'.

[0301] With the downlink signals and the uplink signals, the marker apparatuses (102) can be configured for both sending and receiving MI signals and information therein to and from the mobile platform (108), thus providing bidirectional or 2-way Mi-based communication with the mobile platform (108).

[0302] Herein, reference to one or more embodiments, e.g., as various embodiments, many embodiments, several embodiments, multiple embodiments, some embodiments, certain embodiments, particular embodiments, specific embodiments, or a number of embodiments, need not or does not mean or imply all embodiments

[0303] As used herein, the term “set” corresponds to or is defined as a non-empty finite organization of elements that mathematically exhibits a cardinality of at least 1 (i .e., a set as defined herein can correspond to a unit, singlet, or single element set, or a multiple element set), in accordance with known mathematical definitions (for instance, in a manner corresponding to that described in An Introduction to Mathematical Reasoning:Numbers, Sets, and Functions , “Chapter 11 : Properties of Finite Sets” (e.g., as indicated on p. 140), by Peter J. Eccles, Cambridge University Press (1998)). Thus, a set includes at least one element. In general, an element of a set can include or be one or more portions of a system, an apparatus, a device, a structure, an object, a process, a procedure, physical parameter, or a value depending upon the type of set under consideration.

[0304] The FIGs. included herewith show aspects of non-limiting representative embodiments in accordance with the present disclosure, and particular structural elements shown in the FIGs. may not be shown to scale or precisely to scale relative to each other. The depiction of a given element or consideration or use of a particular element number in a particular FIG. or a reference thereto in corresponding descriptive material can encompass the same, an equivalent, an analogous, categorically analogous, or similar element or element number identified in another FIG. or descriptive material associated therewith. The presence in a FIG. or text herein is understood to mean “and / or”, i.e., “X / Y” is to mean “X” or “Y” or “both X and Y”, unless otherwise indicated. The recitation of a particular numerical value or value range herein is understood to include or be a recitation of an approximate numerical value or value range, for instance, within + / - 20%, + / - 15%, + / - 10%, + / - 5%, + / - 2.5%, + / - 2%, + / - 1%, + / - 0.5%, or + / - 0%. The term “essentially all” or “substantially” can indicate a percentage greater than or equal to 50%, 60%, 70%, 80%, or 90%, for instance, 92.5%, 95%, 97.5%, 99%, or 100%.

[0305] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

[0306] Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0307] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.Statements- I l l -

[0308] One or more embodiments of the present application have the features of the following Statements.

[0309] 1 A process for remote localization of an object, the process including: a. receiving / determining two or more measurements ("magnetic field measurements") of magnetic fields using at least one magnetometer when the magnetic fields are generated by at least one magnetic field source from two or more respective source locations, when the or each magnetic field source is remote from the or each magnetometer which is in / on an opaque medium such that the magnetic fields penetrate through the medium and / or through a navigable medium (e.g., space, air or water) between the or each magnetic field source and the or each magnetometer (the opaque medium may have a surface, e g., including earth / rock / ice / water, and the or each magnetometer may be buried or submerged in the medium or seated / placed on the opaque medium such that the magnetometer is stationary relative to the opaque medium and so that the magnetometer moves with the medium if the medium moves); b. receiving / determining (and / or measuring / recording) the two or more respective source locations (also referred to as "source stations") of the magnetic field source in three orthogonal dimensions (3D) by determining locations of the magnetic field source when the magnetic field measurements are / were determined (wherein the source locations may be in the opaque medium, or outside the opaque medium and in the navigable medium); and c. numerically estimating (e.g., using an iterative process, and using at least one data processing unit / processor, such as at least one microprocessor) a location ("marker location") of the magnetometer in three orthogonal dimensions (3D) using: i. the two or more magnetic field measurements;ii. the two or more respective source locations; and iii. a mathematical model representing a magnetic dipole of the magnetic field source.

[0310] 2. The process of Statement 1, wherein the magnetic fields are generated while the magnetic field source is a mobile magnetic field source attached to at least one mobile platform (which can include a plurality of configurations, including one or more magnetic field sources attached to the or each mobile platform, and / or two or more mobile magnetic field sources attached to two or more mobile platforms, including one mobile magnetic field source attached to each mobile platform), including using magnetic field measurements made while a speed of the or each mobile magnetic field source is substantially non-zero (in a reference frame of the magnetometer and the opaque medium), wherein the mobile platform is configured to move relative to the magnetometer and the opaque medium, optionally wherein the mobile platform is configured to move in the opaque medium and / or outside the medium, which may include on the surface of the medium (e.g., for earth / rock / ice or water) and / or flying / floating substantially off the surface (e.g., above a mine bench or along a mine tunnel), and optionally wherein the magnetic field measurements are made while the mobile magnetic field source is travelling along a path including the source locations.

[0311] 3. The process of Statement 2, wherein the substantially non-zero speed includes from slightly above zero meters per second (m / s) to substantially 30 m / s, including from above zero to 25 m / s, including from above zero to substantially 3 to 4 m / s (e.g., for a multi-rotor drone, e g., for mining or quarrying operations), and substantially 8 m / s to substantially 25 m / s (e.g., for a fixed wing drone, e.g., for linear operations, e.g., along a ditch or pipeline).10312 ] 4. The process of Statement 2 or 3, including using the one or more mobile platforms, e.g., in the form of one or more remotely controlled and / or autonomous vehicles (referred to as "drones"), including an individual drone or a plurality of such vehicles (referred to as a "drone swarm"), to allow for rapid / convenient coverage of multiple of the source locations (also referred to as "stations") as the mobile platforms move.

[0313] 5. The process of any one of the preceding Statements, wherein the magnetic fields are generated while the magnetic field source is a stationary magnetic field source attached to a fixed point, or stationary at a fixed point, which is a non-mobile point in a reference frame of a site that includes the at least one opaque medium and the magnetometer, which may be a mine frame of reference, or a site frame of reference, or an environment frame of reference.

[0314] 6. The process of any one of the preceding Statements, wherein the marker apparatus and the magnetometer remain stationery during the two or more measurements (e.g., by being buried), with a fixed location and orientation, with respect to the duration of the two or more measurements.

[0315] 7 The process of any one of the preceding Statements, wherein the mathematical model includes relationships between the magnetometer location (and thus a corresponding 3D marker location) and the magnetic field measurements and source locations, thus allowing a one-step solution of the 3D marker location.

[0316] 8. The process of any one of the preceding Statements, including numerically estimating (e.g., using the iterative process) an orientation of the magnetometer, including in three orthogonal dimensions (3D orientation), and estimating an orientation of the marker apparatus (in / on the medium) from the numerically estimated orientation of the magnetometer.

[0317] 9 The process of any one of the preceding Statements, including using a selected strength or moment or a calibration of the magnetic field source to improve precision, optionally wherein the magnetic field source is configured to generate the magnetic fields with a selected strength or moment, which may include a selected value and / or a selected range of values (which may be referred to as a "calibrated range"), and the process uses the selected strength or moment with the mathematical model when numerically estimating the location of the magnetometer.

[0318] 10. The process of any one of the preceding Statements, including using a selected sensitivity of the magnetometer to improve efficiency of the localization, optionally wherein the magnetometer is configured to measure the magnetic fields with a selected sensitivity(e.g., represented by a 3x3 matrix when the magnetometer is 3 -axis magnetometer where the alignment / orthogonality of the axes is calibrated), optionally wherein the magnetometer sensitivity includes a selected set of values and / or a selected range of values (which may be referred to as a "calibrated sensitivity range") based on factory calibration and / or calibration measurements, optionally wherein the process uses the sensitivity with the mathematical model when numerically estimating the location of the magnetometer.10319] 11. The process of any one of the preceding Statements, wherein the marker apparatus is configured to measure / control the orientation of the magnetometer, and the process uses the measured / controlled orientation of the magnetometer with the mathematical model when numerically estimating the location of the magnetometer.

[0320] 12. The process of any one of the preceding Statements, including: a. receiving / determining (and / or measuring / recording or controlling) one or more orientations (each being in ID to 3D, e.g., depending on the type of the magnetometer of the magnetometer in three orthogonal dimensions (3D orientation) (thus determining the orientation(s) of the magnetometer when the magnetic field measurements are / were determined); and b. numerically estimating (e.g., using the iterative process) the location of the magnetometer in the three orthogonal dimensions (3D) using a combination of: i. the two or more magnetic field measurements; ii. the two or more respective source locations; iii. the mathematical model representing the dipole of the magnetic field source; and iv. the one or more magnetometer orientations.

[0321] 13. The process of the preceding Statement, wherein the one or more magnetometer orientations are substantially mutually equal, and are measured / recorded only once while thestationary marker apparatus is in that orientation, optionally before, during and / or after the magnetic field measurements are recorded.

[0322] 14. The process of any one of the preceding Statements, wherein the mathematical model associates the magnetic field measurements, the determined locations in 3D, and the 3D locations of the magnetic dipole provided by the magnetic field source, optionally wherein the mathematical model assumes that the medium is homogeneous, and / or that the medium has a skin depth substantially approaching infinity for frequencies at which the magnetic field is modulated.

[0323] 15. The process of any one of the preceding Statements, including: a. recei ving / determining (and / or measuring / recording) two or more respective orientations of the magnetic field source at the two or more source locations in three orthogonal dimensions (3D orientation) (thus determining the orientations of the magnetic field source when the magnetic field measurements are / were determined); and b. numerically estimating (e.g., using an iterative process) the location of the magnetometer in the three orthogonal dimensions (3D) using a combination of: i. the two or more magnetic field measurements; ii. the two or more respective source locations; iii. the mathematical model representing the dipole of the magnetic field source; and iv. the two or more respective magnetic field source orientations.

[0324] 16. The process of the preceding Statement, wherein the determining of the two or more orientations of the magnetic field source includes: a. determining (e g., measuring) one or more orientations of the mobile platform;b. determining (e g., measuring) one or more relative orientations of the magnetic field source to the mobile platform; and c. estimating the two or more orientations of the magnetic field source based on numerical addition / subtraction of the orientations of the mobile platform and the relative orientations

[0325] 17. The process of any one of the preceding Statements, wherein the determining of the two or more source locations includes: receiving / determining respective magnetic-field- measurement times when the magnetic field measurements are / were measured (e.g., recorded by the marker apparatus as the magnetic field measurements are made); and determining the respective locations of the magnetic field source at the magnetic-field-measurement times from location tracking data representing the location of the or each magnetic field source over time, optionally using a data acquisition component that is separate / remote from the marker apparatus and / or on a data acquisition component that is separate / remote from the marker apparatus (e.g., in / on a stationary platform), and optionally recording the location tracking data representing the source locations of the magnetic field source over time using a navigation module moving with the magnetic field source / or using a remote location tracking system that tracks the path / location of the magnetic field source with respect to time.

[0326] 18. The process of any one of the preceding Statements, wherein the magnetometer includes one or more of the following magnetometers: a. a total field magnetometer configured to measure a total scalar value of the magnetic field at the marker location regardless of its direction; b. a vector magnetometer configured to measure a value of the magnetic field in each of one to three orthogonal dimensions (ID, 2D or 3D), and wherein the two or more magnetic field measurements can be non-coherent vector magnetic field measurements; and c. a coherent vector magnetometer configured to measure a phasor value of the magnetic field in each of one to three orthogonal dimensions (ID, 2D or 3D),and wherein the two or more magnetic field measurements are phasor magnetic field measurements.

[0327] 19. The process of any one of the preceding Statements, wherein the measurements of the magnetic field include one or more of: scalar magnetic field strength values, vector magnetic field strength values, and phasor magnetic field strength values.

[0328] 20. The process of any one of the preceding Statements, wherein the determining of the two or more source locations include: a. determining (e g., measuring) locations of the mobile platform; b. determining (e g., measuring) a relative location of the magnetic field source to the mobile platform; and c. estimating the two or more measurement locations based on numerical addition / subtraction of the locations of the mobile platform and the relative location.

[0329] 21 . The process of any one of the preceding Statements, wherein the determining of the measurements of the magnetic field includes the magnetometer detecting magnetic- induction (MI) signal s / through-the-earth (TTE) signals from the magnetic field source.

[0330] 22. The process of any one of the preceding Statements, wherein the 3D locations include three Cartesian values or three spherical values.

[0331] 23. The process of any one of the preceding Statements, wherein the mathematical model includes: a. a closed-form mathematical model with a system of closed-form equations (mathematical relationships); or b. a numerical integration model (e.g., a finite element analysis (FEA) model).

[0332] 24. The process of the preceding Statement, wherein the closed-form equations represent solutions to Maxwell's equations for an (infinitesimal) magnetic dipole in aconducting / permeable medium with a simple structure, and the numerical integration model represents integration of Maxwell's equations for a magnetic dipole in a conducting / permeable medium with any structure.

[0333] 25. The process of any one of the preceding Statements, wherein the mathematical model uses a magnetic dipole modelled as an infinitesimal magnetic dipole (where the distance to the magnetometer is far larger than the size of the magnetic field source), or wherein the magnetic field source is modelled as a loop / coil of finite extent, in which case the strength of the magnetic field source is described by the current, turn shape and area and number of turns rather than by the dipole moment.

[0334] 26. The process of any one of the preceding Statements, wherein the localization process includes the data processing unit(s) / microprocessor(s) receiving the one or more orientations of the magnetic field source from the mobile platform or location tracking system.

[0335] 27. The process of any one of the preceding Statements, wherein the localization process includes the data processing unit(s) / microprocessor(s) receiving: the selected / determined strength of the moment of the magnetic field source from the calibration process; and / or the selected / determined sensitivity of the magnetometer from the corresponding calibration process.

[0336] 28. The process of any one of the preceding Statements, wherein the localization process includes the data processing unit(s) / microprocessor(s) receiving the two or more magnetic field measurements from the magnetometer.

[0337] 29. The process of any one of the preceding Statements, wherein the localization process includes the data processing unit(s) / microprocessor(s) receiving the two or more respective source locations, optionally from a tracking module (e.g., a navigation module (118) attached to the mobile platform (108), and / or a remote location tracking system).

[0338] 30. The process of any one of the preceding Statements, wherein the localization process includes the data processing unit(s) / microprocessor(s) receiving the two or moreorientations of the magnetic field source from a relative pose measurement system and / or the tracking module.

[0339] 31 The process of any one of the preceding Statements, including making the plurality of magnetic field measurements with respective SNRs or magnetic field strengths, and selecting ones of the magnetic field measurements having SNRs or magnetic field strengths over a selected threshold for the numerically estimating of the magnetometer location.

[0340] 32. The process of any one of the preceding Statements, including localizing at least a portion of a drill bit or drill string by localizing a corresponding marker apparatus during drilling with the drill bit or drill string, or after detachment of the portion from the drill bit or drill string.

[0341] 33. The process of any one of the preceding Statements, including localizing a blast initiation device or a blast primer device for initiating blasts in commercial blasting operations based on the localization of at least one marker apparatus that is attached to or includes or forms the blast initiation device or the blast primer device.

[0342] 34. The process of any one of the preceding Statements, including localizing an explosive material in the opaque medium by localizing at least one marker apparatus buried in a selected location in the opaque medium relative to and / or adjacent to and / or above the explosive material, optionally while digging / excavating a portion of the opaque medium or after the digging / excavating.

[0343] 35. The process of any one of the preceding Statements, including localizing seismic receivers and / or seismic sources by localizing the marker apparatuses respectively incorporated in or attached to the seismic receivers and / or the seismic sources.

[0344] 36. The process of any one of the preceding Statements, including monitoring movement of broken rock (e.g., in a heap) by repeatedly localizing the marker apparatus placed on or buried in the broken rock.

[0345] 37. The process of any one of the preceding Statements, including tracking an ore body during blasting, excavation and / or processing by the localization of the corresponding marker apparatuses, optionally including measuring draw of a stockpile by repeated localization of the corresponding marker apparatuses over a selected time period.

[0346] 38. The process of any one of the preceding Statements, including a wireless MT receiver component on the mobile platform gathering wireless encoded / modulated data signals from devices, in / on the opaque medium, incorporating the marker apparatuses, and / or capturing optical / thermal images, while on a path generating the magnetic fields.

[0347] 39. The process of any one of the preceding Statements, including localizing a linear utility (e.g., a pipeline / powerline) in the opaque medium by localizing at least one marker apparatus buried in a selected location in the opaque medium relative to and / or adjacent to and / or above the linear utility, optionally while digging / excavating a portion of the opaque medium above the linear utility.

[0348] 40. The process of any one of the preceding Statements, including localizing measured physical parameters of the opaque medium (e.g., pressure, moisture, and / or temperature) by localizing at least one marker apparatus buried in the opaque medium with respective environmental sensors in / on the marker apparatus to measure the physical parameter values, optionally while ploughing the opaque medium adjacent / around the buried marker apparatus.

[0349] 41. The process of any one of the preceding Statements, including localizing a person or a piece of equipment buried in the opaque medium, e g , an avalanche, a landslide, or a (collapsed) structure, by localizing at least one marker apparatus attached to the person or the piece of equipment in the opaque medium.

[0350] 42. The process of any one of the preceding Statements, including placing / burying the at least one marker apparatus on / in the opaque medium (e.g., rock, earth, foundations or structures), and localizing the marker apparatus repeatedly over a selected time period to monitor movement of the opaque medium.

[0351] 43. A system for remote localization of an object, the system including: a. at least one magnetometer configured for determining (e.g., measuring) two or more measurements ("magnetic field measurements") of two or more respective magnetic fields when the magnetic fields are generated by at least one magnetic field source that is remote from the or each magnetometer, wherein the or each magnetometer is in an opaque medium such that the magnetic field extends through the opaque medium and / or through a navigable medium between the magnetic field source and the or each magnetometer; b. a tracking module (e.g., a navigation module attached to a mobile platform, and / or a remote location tracking system) configured for determining (including measuring / recording) two or more respective locations ("source locations") of the magnetic field source in three orthogonal dimensions (3D) when the magnetic field measurements are / were determined (wherein the source locations may be in the opaque medium or outside the opaque medium); and i. at least one data processing unit / microprocessor configured for numerically estimating a location ("measurement location") of the or each magnetometer in three orthogonal dimensions (3D) using: ii the two or more magnetic field measurements; iii. the two or more respective source locations, and iv a mathematical model representing a magnetic dipole of the magnetic field source.

[0352] 44. The system of Statement 43, wherein the magnetic field source includes at least one mobile magnetic field source attached to at least one mobile platform, optionally wherein the or each magnetic field source includes a plurality of mobile magnetic field sources attached to the or each mobile platform, optionally wherein the or each magnetic field sourceincludes two or more mobile magnetic field sources attached two or more mobile platforms, optionally including one mobile magnetic field source attached to each mobile platform.

[0353] 45. The system of Statement 43 or 44, wherein the tracking module including a navigation module attached to the mobile platform and configured for measuring the 3D source locations of the magnetic field source, or wherein the tracking module include a remote location tracking system configured for recording the 3D source locations in a path of the mobile platform during the measuring of the magnetic field measurements, and time stamping the 3D source locations.

[0354] 46. The system of any one of Statements 43 to 45, wherein the or each magnetic field source includes at least one stationary magnetic field source attached to a fixed point, or stationary at a fixed point, in a reference frame of a site that includes the opaque medium and the marker apparatus.

[0355] 47. The system of any one of Statements 43 to 46, wherein the data processing unit / microprocessor is configured for numerically estimating an orientation of the magnetometer, including in three orthogonal dimensions (3D orientation), and estimating an orientation of the marker apparatus (on / in the medium) from the numerically estimated orientation of the magnetometer.

[0356] 48. The system of any one of Statements 43 to 47, wherein the magnetic field source is configured to generate the magnetic fields with a selected strength or moment, which may include a selected value and / or a selected range of values (which may be referred to as a "calibrated strength range"), and the data processing unit / microprocessor is configured for using the selected strength or moment with the mathematical model when numerically estimating the location of the magnetometer.

[0357] 49. The system of any one of Statements 43 to 48, wherein the marker apparatus is configured to measure / control the orientation of the magnetometer, and the data processing unit / microprocessor is configured for using the measured / controlled orientation of the magnetometer with the mathematical model when numerically estimating the location of the magnetometer

[0358] 50. The system of any one of Statements 43 to 49, including a relative pose measurement system and / or a navigation module configured for determining (e.g., measuring) two or more orientations of the magnetic field source at the two or more source locations in three orthogonal dimensions (3D orientation), wherein the data processing unit / microprocessor is configured for numerically estimating the location of the magnetometer in the three orthogonal dimensions (3D) using a combination of: a. the two or more magnetic field measurements; b. the two or more respective source locations; c. the mathematical model representing the dipole of the magnetic field source; and d. the two or more magnetic field source orientations.

[0359] 51. The system of any one of Statements 43 to 50, wherein the magnetometer includes one or more of: a. a total magnetometer configured to measure a total scalar value of the magnetic field at the measurement location, regardless of its direction; b. a vector magnetometer configured to measure a value of the magnetic field in each of one to three orthogonal dimensions (ID, 2D or 3D), wherein the two or more magnetic field measurements are non-coherent vector magnetic field measurements; and c. a coherent vector magnetometer configured to measure a phasor value of the magnetic field in each of one to three orthogonal dimensions (ID, 2D or 3D), wherein the two or more magnetic field measurements are phasor magnetic field measurements, including a recorded relative phase between the orthogonal components.

[0360] 52. The system of any one of Statements 43 to 51, wherein the magnetometer is configured to measure the magnetic fields with a selected sensitivity, which may include aselected set of values and / or a selected range of values (which may be referred to as a "calibrated sensitivity range"), and the data processing unit / microprocessor is configured to use the selected sensitivity with the mathematical model when numerically estimating the location of the magnetometer.

[0361] 53. The system of any one of Statements 43 to 52, including at least one marker apparatus substantially adjacent to, coupled to or incorporated into a drill bit or a drill string.

[0362] 54. The system of any one of Statements 43 to 53, including at least one marker apparatus that includes or forms a blast initiation device or blast primer device for initiating blasts in commercial blasting operations.

[0363] 55. The system of any one of Statements 43 to 54, including at least one marker apparatus buried in a selected location in the opaque medium relative to and / or adjacent to and / or above explosive material.

[0364] 56. The system of any one of Statements 43 to 55, including at least one marker apparatus incorporated respectively into or with seismic receivers (e.g., hydrophones / geophones) and / or seismic sources (e.g., blasting devices) for seismic surveying.

[0365] 57. The system of any one of Statements 43 to 56, including at least one marker apparatus buried in broken rock (e.g., in a heap).

[0366] 58. The system of any one of Statements 43 to 57 including at least one marker apparatuses buried adjacent to or in an ore body (e.g., down a borehole).

[0367] 59. The system of any one of Statements 43 to 58, wherein the mobile platform include a wireless MI receiver component configured for receiving wireless encoded / modulated data signals from devices in / on the opaque medium.

[0368] 60. The system of any one of Statements 43 to 59, wherein the mobile platform includes at least one optical / thermal camera configured to capture images from the mobileplatform while the mobile platform travels along a path and makes the magnetic field measurements.

[0369] 61. The system of any one of Statements 43 to 60, including at least one marker apparatus buried in a selected location in the opaque medium relative to and / or adjacent to and / or above a linear utility (e.g., a pipeline / powerline) in the opaque medium.

[0370] 62. The system of any one of Statements 43 to 61, wherein the marker apparatus includes one or more environmental sensors configured to detect, monitor, estimate, or measure physical parameters of the surrounding portion of the opaque medium, and the environmental sensors may include temperature sensors and / or moisture sensor (e.g., for soil monitoring).

[0371] 63. The system of any one of Statements 43 to 62, including at least one marker apparatus incorporated into a marker beacon for mountain workers or engineering workers, e.g., attached or incorporated in clothing, modified ski passes / access tags, and / or smartphone cases / power banks.

[0372] 64. The system of any one of Statements 43 to 63, including an uplink channel from the marker apparatus for transferring uplink information, including: the two or more magnetic field measurements (optionally with respective times or other information representing the respective source locations); and optionally the one or more orientations of the magnetometer

[0373] 65. The system of any one of Statements 43 to 64, wherein the marker apparatus includes an accelerometer and / or a magnetometer configured to measure an orientation of the magnetometer when stationery relative to Earth's gravity and / or the Earth's magnetic field (or "geomagnetic field").

[0374] 66. A marker apparatus for localizing buried objects, the marker apparatus including: a. an accelerometer and / or a magnetometer configured to measure an orientation of a magnetometer of the marker apparatus when stationery relative to Earth's gravity and / or the Earth's magnetic field (or "geomagnetic field"); andb. a marker wireless MI transmitter component (e.g., including a through-the- earth (TTE) or magnetic induction (MI) transmitter with a transmit antenna) in the marker apparatus configured to transmit an uplink signal representing the uplink information (mentioned hereinbefore) through the medium (in which the marker apparatus is stationery, which may have a surface, e.g., including earth / rock / ice / water) such that the measured magnetometer orientation can be used to estimate a location of the marker apparatus in three orthogonal dimensions (3D).

[0375] 67. The marker apparatus of Statement 66, wherein the uplink information is transmitted from the marker apparatus via a wireless MI uplink signal to the wireless MI receiver component, which is optionally in or outside the medium, and / or via a wireless MI multihop signal between a pair of the marker apparatuses, which may be in or outside the medium.

[0376] 68. The marker apparatus of Statement 67, configured to communicate uplink information via the uplink signals (optionally in a different channel) such that the mathematical model is informed of the orientation in space.

[0377] 69. A marker apparatus for localizing buried objects, the marker apparatus including: a. an accelerometer and / or a magnetometer configured to measure an orientation of a magnetometer of the marker apparatus when stationery relative to Earth's gravity and / or the Earth's magnetic field, and b. a microcontroller configured to control the magnetometer in the marker apparatus based on the measured orientation of the magnetometer such that the magnetometer measures a magnetic field with a selected orientation (e g., such that the measured magnetic field is equivalent to that of coil with an axis controlled by the microcontroller).APPENDIX A: Coherent Vector Process - determining P&O of a marker (iterative)In these Appendices, bold face indicates a vector or matrix quantity, while plain face is a scalar. E g. r — ||r||. The marker P&O variables are usually written in the form of a ‘tracking matrix’ P, and an ‘orientation matrix’ As, as described in Kuipers JB, others (1999) "Quaternions and rotation sequences". Princeton University Press, Princeton. This allows the forward model to be factorised into a rotation sequence, simplifying algebraic manipulation. d stores n measurements of the source position vector, over the course of the mission (where the source locations may be referred to herein as n "stations" or "source stations") b stores n corresponding measurements of the magnetic flux density vector by the marker.Amstores n corresponding measurements of the source orientations x stores a list of values for the unknown marker variables (position vector R, orientation Euler angles ip,9 and < / > (thus allowing for a marker (102) that has a three-axis magnetometer (106) and hence needs three orientation angles to describe its orientation), and sensitivity calibration K)1 : d «- populated with data from vehicle GNSS-INS and any source-vehicle relative displacement2: b «- populated with data from magnetometer3 : Am<- populated with data from the source orientation measurement4: Ro«- populated from prior information on marker location (e.g., approximate estimates)5: ipQ, 60, (p0<- arbitrary starting guess6: Ko<- nominal design sensitivity7:8: x <- x0iteration variable (marker unknowns)9: while cost > tol do standard non-linear (global) optimisation routines10: cost <- CostFunction(x, d, b, Am)11 : x <- NewGuess(x, d, b, Am)12: Function CostFunction(x, d, b,Am) coherent vector process13: r <r- R — d14:<- aero(i / j, 6, <p) a rotation matrix (ZYX aerospace sequence)15: for i = 1 to n do16: Pi «- tracking(rj)17: Ct coupling^)18: simplest cost function, using the forward model directly19: cost — Z ' ifl sum of squares of cost at each station20: Function NewGuess(x, d, b, Am) e.g., processes such as MATLAB’s IsqnonlinQ functionAPPENDIX B: cost function: Marker antenna orientation known list of unknown marker variables is now only 3DoF (position only). Don’t iterateon orientation.1 : Function CostFunction(x, d, b, Am) a coherent vector process2: r <- R — d3 : As<- aero() / y 3, (f>) marker Euler angles ip, 3 and <p known from the IMU and compass9: For a marker with an IMU but no compass (incomplete orientation information), x becomes:10: x list of unknown marker variables includes orientation angles, however theseangles’ allowed values in the optimisation are constrained by data from the onboard marker IMU.11 : For a marker that contains a self-righting antenna (magnetometer) with a single coil with a vertical axis, the above are modified as:snstant, known rotation matrix, and the\RJ three-element vectorbecomes the scalar ftbecause only one vector component b: of the field vector btis measured.APPENDIX C: cost functions: Total field process b <- magnetometer data, which may be in the magnetometer frame in this case (as opposed to the global frame). Phase / sign of b not required. Vector components of b not necessarily required (only total field).APPENDIX D: Absolute value process (of vector components) b <- magnetometer data, only magnitude of each component of b required.1 : Function CostFunction(%, d, b, Am)2:3:4:5:6:7:8:9: For a marker with an IMU and compass onboard, Asis a known, constant rotation matrix and the algorithm does not iterate on orientation angles (ip, 6 and < / > are known), so x becomes:10:11 : For a marker with an IMU but no compass, (incomplete orientation information), x becomes: list of unknown marker P&O variables which includes orientation angleshowever the allowed values of the orientation angles are constrained by the measurement of the onboard IMU.13: For a self-righting single-axis marker antenna, the cost function above is modified with:and a constant, known rotation matrix, ft whichwas a three-element vector becomes f which is a scalar. This is because the single axis magnetometer measures just one component bt of the magnetic field vector b.

Claims

CLAIMS:

1. A process for remote localization of an object, the process including: receiving / determining two or more measurements of magnetic fields using at least one magnetometer when the magnetic fields are generated by at least one magnetic field source from two or more respective source locations, when the or each magnetic field source is remote from the or each magnetometer which is in / on an opaque medium such that the magnetic fields penetrate through the medium and / or through a navigable medium between the or each magnetic field source and the or each magnetometer; receiving / determining the two or more respective source locations of the magnetic field source in three orthogonal dimensions by determining locations of the magnetic field source when the magnetic field measurements are / were determined; and numerically estimating a location of the magnetometer in three orthogonal dimensions using: o the two or more magnetic field measurements; o the two or more respective source locations; and o a mathematical model representing a magnetic dipole of the magnetic field source.

2. The process of claim 1, wherein the magnetic fields are generated while the magnetic field source is a mobile magnetic field source attached to at least one mobile platform, including using magnetic field measurements made while a speed of the or each mobile magnetic field source is substantially non-zero.

3. The process of claim 1 or 2, wherein the magnetic fields are generated while the magnetic field source is a stationary magnetic field source attached to a fixed point, or stationary at a fixed point4. The process of any one of claims 1 to 3, wherein the at least one magnetometer includes a plurality of magnetometers in / on respective marker apparatuses.

5. The process of any one of claims 1 to 4, wherein the mathematical model includes relationships between the magnetometer location and the magnetic field measurements and source locations.

6. The process of any one of claims 1 to 5, including numerically estimating an orientation of the magnetometer.

7. The process of any one of claims 1 to 6, including using a selected strength of the magnetic field source to improve precision.

8. The process of any one of claims 1 to 7, including using a selected sensitivity of the magnetometer to improve efficiency.

9. The process of any one of claims 1 to 8, including receiving / determining two or more respective orientations of the magnetic field source at the two or more source locations, and numerically estimating the location of the magnetometer using the two or more respective magnetic field source orientations.

10. The process of any one of claims 1 to 9, including receiving / determining two or more respective orientations of the magnetometer during the two or more measurements, and numerically estimating the location of the magnetometer using the two or more respective magnetometer orientations.

11. The process of any one of claims 1 to 10, including receiving / determining respective magnetic-field-measurement times when the magnetic field measurements are / were measured, and determining the respective locations of the magnetic field source at the magnetic-field-measurement times from location tracking data representing the location of the or each magnetic field source over time.

12. The process of any one of claims 1 to 11, including the magnetometer measuring a total scalar value of the magnetic field at the at the marker location, regardless of its direction.

13. The process of any one of claims 1 to 12, including the magnetometer measuring a value of the magnetic field in each of one to three orthogonal dimensions.

14. The process of any one of claims 1 to 13, including the magnetometer measuring a phasor value of the magnetic field in each of one to three orthogonal dimensions15. The process of any one of claims 1 to 14, wherein the mathematical model includes a closed-form mathematical model with a system of closed-form equations, or a numerical integration model.

16. The process of any one of claims 1 to 15, including making the plurality of magnetic field measurements with respective SNRs or magnetic field strengths, and selecting ones of the magnetic field measurements having SNRs or magnetic field strengths over a selected threshold for the numerically estimating of the magnetometer location.

17. A system for remote localization of an object, the system including: at least one magnetometer configured for determining two or more measurements of two or more respective magnetic fields when the magnetic fields are generated by at least one magnetic field source that is remote from the or each magnetometer; a tracking module configured for determining two or more respective locations of the magnetic field source when the magnetic field measurements are / were determined; and- at least one microprocessor configured for numerically estimating a location of the or each magnetometer using: o the two or more magnetic field measurements; o the two or more respective source locations; ando a mathematical model representing a magnetic dipole of the magnetic field source.

18. The system of claim 17, including at least one mobile magnetic field source and / or at least one stationary magnetic field source.

19. The process of any one of claims 1 to 15, including localizing at least a portion of a drill bit or drill string by localizing a corresponding marker apparatus during drilling with the drill bit or drill string, or after detachment of the portion from the drill bit or drill string.

20. The system of claim 17 or 18, including at least one marker apparatus substantially adjacent to, coupled to or incorporated into a drill bit or a drill string.

21. The process of any one of claims 1 to 15, including burying at least one marker apparatus in a selected location in the opaque medium relative to and / or adjacent to and / or above explosive material, optionally in an explosive column with a blast initiation device or blast primer device for initiating the explosive material, such that the marker apparatus can mark the location of the explosive material for safety reasons.

22. The system of claim 17 or 18, including at least one marker apparatus in a selected location in the opaque medium relative to and / or adj cent to and / or above explosive material, optionally in an explosive column with a blast initiation device or blast primer device for initiating the explosive material, such that the marker apparatus can mark the location of the explosive material for safety reasons.

23. The process of any one of claims 1 to 15, including monitoring movement of broken rock, optionally in a heap, by repeatedly localizing a marker apparatus placed on or buried in the broken rock.

24. The system of claim 17 or 18, including at least one marker apparatus buried in broken rock, optionally in a heap.

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