Navigation support method and device

Abstract

A navigation aid method and apparatus for enhanced navigation of an offshore platform (100) on the seabed (200) that uses micro-navigation displacement measurements and estimators to improve navigation data of the offshore platform (100).

Description

[Background technology]

[0001] The present invention relates to a navigation support method according to claim 1 and to a navigation support device according to claim 25.

[0002] background The general concept of measuring displacement by correlating acoustic signals from successive transmissions at a multi-element receiver originates from US 4,244,036 A (Raven, 1978) and EP 0010974 B1 (Dickey 1978).

[0003] EP0010974B1 presents a solution to estimate the full 3D displacement of a downward looking system by estimating the direction of acoustic reflections relative to a 2D array. Displacement along the line of sight is estimated from the time delay and displacement in the array plane from correlated elements.

[0004] US 4,244,036A is based on estimating the approximate lateral displacement from the time delay of the system viewed from the side.

[0005] Another solution is known from US6304513B1 (Billon, 1998) which discloses the estimation of the roll angle from sonar to the seabed by using interferometry, achieving a more accurate orientation with respect to the displacement associated with the time delay.

[0006] The estimation of general motion along the array for side view geometry is closely related to the disclosure of EP0010974B1.

[0007] However, the acoustic signal decorrelates rapidly only along the axis where the acoustic footprint is wide. For a side-viewed shape, this corresponds to the direction along the general trajectory. Thus, by correlating the acoustic signals from successive transmissions, for a side-viewed system, only two components of the displacement are available for a particular range and side. The magnitude of the third component of the displacement remains unknown.

[0008] For downward looking geometries, the solution of EP0010974B1 allows estimation of the displacement of the 2D array relative to the line of sight.

[0009] For a side-view geometry, it allows estimating the displacement of the 2D array with respect to the line of sight and one blind / information-free direction, which is orthogonal to both the seafloor and the line of sight.

[0010] To construct a complete displacement vector, both the direction and magnitude of all three components of the displacement are required. If one component is unknown, the displacement orthogonal to the unknown component can be evaluated only if the directions of all three components are known.

[0011] Integrating the displacement vector into a navigation system requires not only the direction and magnitude of the displacement vector, but also the accuracy of their estimates.

[0012] For the downward view of EP0010974B1, the yaw and pitch angles are identical and therefore only one estimate is needed. For the side view, pitch and yaw must be estimated separately.

[0013] Other solutions dedicated to side-view shapes; US 4,244,036, US 6,304,513 B1 and US 10,073,175 B2 (Pinto) all assume that the echo of each ping returns from a broadside direction corresponding to a yaw angle of 90 degrees. US 4,244,036 uses an assumed known roll angle, while US 6,304,513 B1 and US 10,073,175 B2 introduce alternative embodiments of EP 0010974 B1 to estimate either the roll angle or both the roll and pitch angles. The requirement to estimate yaw is not addressed for side-view shapes, reducing the accuracy of the line-of-sight direction assessment and reducing the accuracy of the blind / uninformed direction estimation.

[0014] Furthermore, prior art techniques specific to side-view geometry assumed that the two axes of measurement were orthogonal (as implied by yaw being equal to 0) and applied the displacement measurement as a velocity measurement valid at one particular point in time.

[0015] The simplifications and assumptions of the prior art solutions introduce inaccuracies into the navigation system, following measurement bias in the estimation and drift in the estimated / calculated parameters.

[0016] Especially for underwater systems where global navigation systems relying on electromagnetic signals are not available, speed or displacement sensors are key components of many navigation systems. In scenarios requiring extreme accuracy over long periods of time, it is crucial to eliminate measurement biases, as they accumulate and become a limiting factor in position accuracy over time.

[0017] Therefore, there is a need for a navigation aid method and apparatus that provides improved long term position accuracy compared to prior art solutions.

[0018] Additionally, there is a need for navigational aid methods and apparatus that can model displacement measurements with a higher level of accuracy than is currently available.

[0019] Additionally, there is a need for a navigation aid method and apparatus that treats displacement measurements as non-orthogonal and is able to identify and utilize different coordinate frames when applying the displacement measurements in the system.

[0020] Additionally, a need exists for a navigation aid method and apparatus that can correctly handle different valid times of measurements. Additionally, a need exists for a navigation aid method and apparatus that enhances the accuracy of other sensors carried by the offshore platform.

[0021] the purpose SUMMARY OF THE PRESENT EMBODIMENT It is a primary object of the present invention to provide a navigation aid method and apparatus which overcomes, in part or in whole, the above-mentioned drawbacks of the prior art.

[0022] It is an object of the present invention to provide a navigation aid method and apparatus which provides improved long term position accuracy compared to prior art solutions.

[0023] It is an object of the present invention to provide a navigation aid method and apparatus that is capable of modeling displacement measurements with an unprecedented level of accuracy.

[0024] It is an object of the present invention to provide a navigation aid method and apparatus that can treat displacement measurements as non-orthogonal.

[0025] It is an object of the present invention to provide a navigation aid method and device which allows the use of different coordinate frames when applying displacement measurements in the device.

[0026] It is an object of the present invention to provide a navigation aid method and device capable of dealing accurately with different times.

[0027] Further objects will become apparent from the following specification, claims and accompanying drawings.

[0028] The method for navigation assistance according to the invention is defined by the technical features of claim 1. Preferred features of the method are set out in the dependent claims.

[0029] A navigation aid according to the invention is defined by the technical features of claim 25. Preferred features of the navigation aid are set out in the dependent claims.

[0030] The present invention provides a method and apparatus for aiding navigation using displacement measurements.

[0031] In order to understand the present invention, it is necessary to define some of the coordinate systems used in this disclosure.

[0032] Line of sight is defined in the present invention as the vector extending between the receiver array and the acoustic center of the bottom return.

[0033] The viewing plane is defined in the present invention as the plane spanned by the line of sight and the normal vector of the seabed.

[0034] The receiver array frame is centered over the receiver array with its X-axis (pointing forward) along the main dimension of the receiver array and its Z-axis spanning the second dimension of the 2D array.

[0035] The patch frame is positioned at the acoustic centroid of any stage of illumination of the seafloor, with the Y-axis along the line of sight and the X-axis pointing along the seafloor.

[0036] The offshore platform relative frame has its origin at a reference point on the offshore platform with the X axis in the forward direction, the Y axis in the sideways direction and the Z axis in the vertical direction.

[0037] The navigation frame is a local coordinate system resulting from the lateral-longitudinal position of the offshore platform on the Earth's surface at sea level, with the Z direction pointing towards the centre of the Earth and the X and Y directions freely rotating around the Z direction.

[0038] A geographic navigation frame is an Earth-fixed coordinate system that rotates with the Earth.

[0039] In one example of a geographic navigation frame, an Earth-fixed coordinate system has its origin at the center of the Earth, with one direction pointing north, one direction lying in a plane passing through the equator and pointing 180 degrees east / west, and one direction orthogonal to these (ECEF).

[0040] The navigation aid method and apparatus according to the present invention provide an integrated solution for marine platforms, thus forming an acoustic micro-navigation aided integrated navigation system.

[0041] The present invention relates to the use of displacement measurements of an offshore platform relative to the seabed as the offshore platform moves over the seabed, integrating the displacement measurements into a navigation processor that utilizes one or more other sensors.

[0042] In accordance with the present invention, a navigation aid method and apparatus is configured to determine an offshore platform relative coordinate frame of the displacement measurements in conjunction with integrating the above-mentioned displacement measurements in a navigation processor.

[0043] The device includes at least one single-sided or double-sided sonar consisting of at least one transmitter and at least two (multi-element) receiver arrays, each substantially parallel to the direction of motion of the offshore platform.

[0044] According to one embodiment of the navigation aid, the receiver arrays are stacked approximately perpendicular to both the direction of motion of the offshore platform and the ocean floor.

[0045] In accordance with the present invention, a navigation aid comprises a sonar processor configured to perform displacement measurements between sonar transmissions and to estimate a coordinate frame for each such measurement.

[0046] In accordance with the present invention, the navigation aid comprises a navigation processor configured to combine the displacement measurements with measurements from other sensors integrated into or located on the marine platform, such as an inertial measurement unit (IMU), pressure sensors, and positioning sensors such as a Global Navigation Satellite System (GNSS) receiver to provide an initial position measurement.

[0047] The use of sonar with a side-view geometry allows estimation of the displacement of the 2D array relative to the line of sight and one blind / no information direction, which is orthogonal to both the seafloor and the line of sight, as defined above.

[0048] To construct a complete displacement vector, both the direction and magnitude of all three components of the displacement are required. If one component is unknown, the displacement orthogonal to the unknown component can be estimated, but only if the directions of all three components are known.

[0049] For integration into a navigation aid, not only the direction and magnitude of the displacement vectors are required, but also the accuracy of their estimates.

[0050] According to one embodiment of the present invention, the line of sight yaw angle is estimated to distinguish this side view shape from a down looking sonar shape solution where the yaw and pitch angles are the same.

[0051] Due to the side-view sonar geometry, the yaw angle estimation described above contributes to both an accurate assessment of the line of sight direction and an accurate estimation of the blind / no information direction.

[0052] The present invention provides a navigation aid method and device which correctly treats displacement measurements as non-orthogonal, recognising that several different coordinate frames are relevant for applying the displacement measurements in an (integrated) navigation device.

[0053] The navigation aid method according to the present invention involves performing displacement measurements (delta position) along the principal axes of two different coordinate systems: the receiver array frame and the patch frame.

[0054] The method according to the present invention further includes calculating a complete orientation of the receiver array frame relative to the patch frame.

[0055] According to a further embodiment of the method according to the invention, it further comprises the step of calculating an associated precision for every measurement and calculation. Another embodiment uses a fixed value for said precision.

[0056] The method of navigation assistance according to the invention further comprises the step of registering a number of time stamps for the transmission and reception times and dealing with these during the integration.

[0057] Each ping pair from either the port or starboard side generates a constellation of micro-navigation measurements. Each measurement in the constellation is associated with a patch that is a particular distance from the receiver array, so that each measurement is valid at a slightly different time. The navigation aid method according to the invention involves calculating angles to estimate the patch coordinate system (to provide improved estimates of line of sight and view plane) and displacement measurements for each patch measurement obtained from each successive ping pair on each side. The combined output is needed to derive accurate velocity updates for the integrated navigation aid.

[0058] The number of patches (per ping) that make up the constellation described above is configurable according to the present invention, and the location of the patches on the seabed relative to the moving offshore platform is either static or dynamic.

[0059] According to another embodiment of the present invention, the navigation assistance method further includes correlating elements along the trajectory to estimate an azimuth direction of the line of sight.

[0060] In another embodiment of the method according to the invention, the navigation assistance method includes using ping data to estimate the scattering distribution on the patch to estimate the azimuth direction of the line of sight.

[0061] According to another embodiment of the invention, a navigation aid method includes using ping data to estimate seabed depth in multiple azimuth directions and ranges to estimate effective seabed slope, which is used in conjunction with the line of sight to determine a viewing plane spanning the YZ plane in the patch frame.

[0062] The navigation aid method according to the invention includes using an estimator such as a Kalman filter (KF) or an extended Kalman filter, a non-linear estimator such as an unscented Kalman filter, a particle filter, a sensor fusion method, machine learning or other similar solutions. The estimator according to the invention is used to model the relationship between the navigational state (hereinafter position, orientation and velocity) of the marine platform and the micro-navigation displacement measurements, coordinate frames, timing and associated accuracy. According to another embodiment of the invention, the estimator is further used to estimate sensor errors such as offset and scaling errors.

[0063] According to another embodiment of the navigation aiding method, it includes using an estimator to model the relationship between the navigation aiding states (hereinafter position, orientation, and velocity) of the offshore platform and measurements and / or states from additional sensors, such as an inertial measurement unit (IMU), gyrocompass, or similar unit.

[0064] According to another embodiment of the navigation assistance method according to the invention, it comprises using an estimator to estimate systematic errors in any measurements and calculations including micro-navigation, such as, but not limited to, micro-navigation displacement measurements and / or installed geometry.

[0065] According to another embodiment of the present invention, a navigation assistance method includes calibrating different device parameters, such as micro-navigation scale factor error, transducer alignment error, etc., by incorporating additional states into the estimator.

[0066] In accordance with the present invention, a method for aiding navigation involves predicting the variance estimates and their error covariances between aiding measurements, and updating them each time a new measurement is accepted.

[0067] The theoretical accuracy and full utilization of micronavigation imposes stringent requirements on mathematical implementation and timing. The navigation assistance method according to the present invention involves integrating micronavigation measurements that accurately incorporate and utilize available information without the approximations and assumptions of prior art methods.

[0068] The final objective of the navigation aid method according to the invention is to utilize micro-navigation measurements to reduce the velocity error and therefore the position error of the (integrated) navigation aid device (which means reducing the position drift). Compared to traditional velocity aid techniques (which use additional sensors), micro-navigation provides a higher fidelity input.

[0069] Each micro-navigation displacement measurement is linked to its state in the estimator, but the actual processing steps are the same. When considering an iteration with a single micro-navigation displacement measurement, the navigation assistance method according to the invention involves registering and converting the micro-navigation displacement measurement (delta position) to the estimator measurement by the navigation processor, by combining the transmission time and reception time to convert the displacement in a particular coordinate system to a velocity.

[0070] According to a further embodiment of the navigation assistance method according to the invention, it comprises using the displacement accuracy either directly or indirectly by converting it into a velocity accuracy.

[0071] The representations in the different coordinate frames remain unchanged at this point, and the non-orthogonality is correctly handled when performing the lever arm compensation and estimator updating further described below.

[0072] A method of navigation aiding in accordance with the present invention includes performing, by the navigation processor, micro-navigation lever arm compensation as part of the estimator measurement calculations. In another embodiment of the method of navigation aiding, the lever arm compensation is performed as part of the displacement measurement registration.

[0073] According to the navigation aid method of the present invention, it involves calculating the lever arm with a static portion from the mechanical offset from the navigation aid origin to the sonar transmitter and multiple receiver array and a dynamic portion due to the changing overlap caused by the surge motion of the offshore platform.

[0074] In this manner, the navigation aid method compensates, through lever arm calculations, for the effects that the lever arm has on the micro-navigation displacement measurement and the associated compensations for: angular velocity of the marine platform, intermediate rotations that occur during the time periods between different patch orientations and the micro-navigation displacement measurement, and rotational misalignment of the receiver array relative to the navigation frame.

[0075] According to one embodiment of the present invention, in the navigation aid method according to the present invention, the calculated lever arms are resolved into either the receiver array frame or the patch frame for each of the aforementioned displacement measurements.

[0076] In accordance with the present invention, the navigation assistance method further includes computing, by the estimator, corrections based on estimates of the estimator observation model and the accuracy of the computed micro-navigation displacement and orientation measurements.

[0077] In accordance with the present invention, the accuracy of the micro-navigation displacement and orientation measurements is calculated as a function of the navigation device velocity (geographic navigation frame), the micro-navigation surge velocity (receiver array frame), and the micro-navigation sway velocity (patch frame), with all lever arms compensated. In accordance with the present invention, the non-orthogonality of the different displacement measurements is compensated for by the navigation processor.

[0078] According to one embodiment of the navigation assistance method of the present invention, the navigation assistance method includes adapting the displacement measurements in the navigation frame by taking into account intermediate rotations that occur in the period between the different times of the patch orientation and the micro-navigation displacement measurements.

[0079] According to further embodiments, the rotational misalignment of the receiver array with respect to the navigation frame and / or the orientation of the acoustic estimation patch coordinate system (intensity distribution and spatial extension) may also be taken into account.

[0080] In accordance with the present invention, the navigation aid method includes correcting displacement measurements in the receiver array frame by applying an orientation of the acoustic estimation patch coordinate system.

[0081] According to the navigation assistance method of the present invention, the accuracy of the micro-navigation and orientation measurements and the output of the estimator observation model described above are decomposed two-dimensionally in the patch frame.

[0082] The navigation assistance method of the present invention utilizes an estimator observation model that describes the connections between navigation states, the errors in the navigation states, and the modeled errors in the micronavigation displacement measurements and orientations of the patches.

[0083] According to another embodiment of the navigation aid method of the invention, for calibration it comprises incorporating calibration states and combining them in an estimator.

[0084] A method for navigation assistance according to an embodiment of the present invention includes decomposing errors in the navigation state in a geographic navigation frame, and the construction of this part of the observation matrix takes into account the same effects of the errors mentioned above in the measurement derivation, and more particularly, takes into account intermediate rotations that occur during the period between different times of patch orientation and micronavigation displacement measurements.

[0085] According to another embodiment of the invention, the rotational misalignment of the receiver array with respect to the navigation frame and / or the orientation of the acoustic estimation patch coordinate system (intensity distribution and spatial extension) may also be taken into account.

[0086] The micro-navigation portion of the observation matrix described above is parameterized, in accordance with the navigation assistance method of the present invention, such as, but not limited to, linearization, curve fitting, etc., around the solution of the navigation equations, and patch angles.

[0087] In another embodiment of the present invention, the above-mentioned estimator observation matrix is ​​implemented by a non-linear estimator, and the above-mentioned parameterization is not required.

[0088] According to one embodiment of the navigation assistance method according to the invention, it comprises using a Kalman filter or an extended Kalman filter as estimator.

[0089] As with the observation matrix, the navigation aid method according to the invention includes, for the micro-navigation portion, calculating an observation noise matrix, based on the accuracy reported by the sonar processor, optionally in combination with configuration parameters. More specifically, the navigation aid method according to one embodiment includes parameterizing the observation equations and patch angles around the solution of the navigation equations. Given the parameterized model, the observation noise matrix can be found according to the invention using a similarity transformation, the accuracy of the surge and sway measurements, and the patch angles.

[0090] The method of navigation assistance according to an embodiment of the present invention further includes providing the corrections as inputs to a controller or control system that directly or indirectly controls the motion of the marine platform. The corrections may involve estimation gains, such as Kalman filter gains when a Kalman filter is used. The estimation gains are, for example, relative weights given to measurements and current state estimates.

[0091] The above navigational aid methods may be modified for different applications.

[0092] According to an embodiment of the present invention, a navigation aid method according to a further embodiment includes converting micro-navigation displacement measurements (delta positions) into velocity measurements applicable to a pre-set / desired time interval. This embodiment can be further improved by using inertial measurement unit measurements, for example by correcting or correcting the time of the measurements to a better location than the pre-set / desired time interval. For marine platforms that experience only low acceleration movements, the errors of this method are rather small.

[0093] Another application modification focuses on dealing with the acceleration of the marine platform in a better way, where it can be assumed that the errors progress slower than in the perfect state. For such applications, the navigation aid method according to the invention involves estimating the expected micronavigation displacement measurements (delta position) by integrating the inertial measurement unit measurements (navigation equations) and comparing the two. A further advantage of this embodiment is that no new states need to be added to the estimator observation model.

[0094] According to a further embodiment of the navigation assistance method according to the invention, it includes using near optimal micro-navigation displacement measurements (delta positions) by using additional states to "remember the position and its correlation" from the start to the completion of the displacement measurement. The advantage of this embodiment is that it requires almost no assumptions.

[0095] Thus, in accordance with the present invention, a navigation aid method and apparatus is provided that uses displacement measurements from sonar to improve real-time navigation of an offshore platform over the seabed. By providing improved real-time navigation of the offshore platform, enhanced and more accurate control of the offshore platform over the seabed is also achieved.

[0096] In particular, the present invention contributes to reducing position drift.

[0097] A navigation support device according to the present invention, which is based on the principles of a navigation support method, will now be described in detail.

[0098] Further preferred features and advantageous details of the invention emerge from the following exemplary description, the claims and the accompanying drawings. [Brief description of the drawings]

[0099] example The present invention will now be described in more detail with reference to the accompanying drawings. [Figure 1] 1 is a diagram illustrating the principle of a navigation support device according to the present invention; [Diagram 2] FIG. 1 is a principle diagram of an offshore platform equipped with sonar moving over the seabed and associated coordinate systems. [Diagram 3] FIG. 1 is a diagram illustrating the principle of the shape and timing of displacement measurement. [Figure 4] FIG. 1 is a diagram illustrating the principle of relative line of sight for measuring sway displacement. [Diagram 5] FIG. 1 is a diagram showing the principle of the relative viewing plane of surge displacement measurement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0100] Reference is now made to Figures 1 and 2. Figure 1 shows a principle diagram of a navigational aid 10 according to the invention adapted to be located or integrated on an offshore platform 100. Figure 2 shows the navigational aid 10 and associated coordinate systems located on the offshore platform 100 moving above the seabed 200.

[0101] The offshore platform 100 is typically a submersible, submersible or semi-submersible vehicle that moves generally forward at a desired height above the ocean floor 200. The offshore platform 100 is typically an autonomous or semi-autonomous vehicle.

[0102] The offshore platform 100 is equipped with controllable propulsion means (not shown) or is towed by a ship or craft having propulsion means that allows semi-autonomous or autonomously controlled movement of the offshore platform 100 through the water. The navigational aid 10 according to the present invention may be used for enhanced navigation information or for input to control the offshore platform 100 or the ship or craft towing the offshore platform 100, or both.

[0103] In the latter case, the offshore platform 100 or ship or craft is provided with a controller or control system (not shown) in communication with the navigational aid 10 according to the invention which controls each of the propulsion means. Propulsion means and controllers or control systems are well known to those skilled in the art and do not require further disclosure here.

[0104] The following coordinate system is shown in FIG. - A receiver array frame XT, YT, ZT centred on the receiver array of the navigation aid 10, where the X axis is along the main dimension of the receiver array (pointing forward) and the Z axis spans the second dimension of the two-dimensional array. a patch frame XP, YP, ZP positioned at the acoustic centroid of any stage of illumination of the seabed 200, where the Y axis is along the line of sight and the X axis points along the seabed 200; - an offshore platform relative frame XM, YM, ZM having its origin at a reference point on the offshore platform 100, where the X axis is forward, the Y axis is sideways and the Z axis is vertical.

[0105] Geographic navigation frame, navigation frame, line of sight and view plane are defined above.

[0106] A navigation aid 10 according to the present invention is configured to perform micro-navigation displacement measurements of the offshore platform 100 relative to the seabed 200 relative to which the offshore platform 100 is moving. A navigation aid 10 according to the present invention is further configured to integrate these displacement measurements into a navigation processor 40 of the offshore platform 100, optionally in combination with one or more additional sensors 50 (if present), which are further described below.

[0107] The navigation aid 10 according to the present invention is further configured to determine an offshore platform relative coordinate frame of the displacement measurements.

[0108] A navigation aid 10 according to the present invention includes at least one single or double sided sonar configured to be carried by an offshore platform 100. In the embodiment shown, the sonar is double sided having a port side transducer 20a and a starboard side transducer 20b. Each transducer 20a-b comprises at least one transmitter 21 and at least two multi-element receiver arrays 22a-b, each arranged substantially parallel to the direction of motion of the offshore platform 100. The receiver arrays 22a-b are typically stacked substantially perpendicular to the direction of motion of the offshore platform.

[0109] The navigation aid 10 according to the present invention further comprises a sonar processor 30 configured to perform micro-navigation displacement measurements between the sonar transmissions and the coordinate frame of each measurement. The navigation aid 10 further comprises a navigation processor 40 having means and / or software for calculating the accuracy of the micro-navigation displacement measurements and the orientation measurements, and an estimator observation module using the micro-navigation displacement measurements. The navigation processor 40 further comprises means and / or software for calculating corrections based on estimates of the estimator observation model and the calculated accuracy of the micro-navigation displacement measurements and the orientation measurements for correction of the navigation data of the offshore platform 100.

[0110] Navigation processor 40 according to further embodiments of the present invention is configured to combine the displacement measurements with measurements from additional sensors 50 located on or integrated into marine platform 100. Examples of additional sensors 50 include, but are not limited to, one or more of an inertial measurement unit (IMU), a pressure sensor, and a positioning sensor such as a Global Navigation Satellite System (GNSS) receiver to provide an initial position measurement.

[0111] The navigation aid 10 further comprises a sonar electronics unit 23 connecting the above-mentioned at least one transmitter 21 and the at least two receiver arrays 22a-b of transducers 20a-b to the above-mentioned sonar processor 30, the trigger control unit 60 and the master clock 70. The sonar electronics unit 23 is configured, among other functions, to provide transmission time and time-stamped time series data from all sonar receive channels to the sonar processor 30. The above-mentioned navigation processor 40 is connected to the sonar processor 30 and configured to receive displacement measurements and coordinate frames with their associated precision and time stamps.

[0112] The trigger control unit 60 is connected to the navigation processor 40 and generates a trigger signal each time the marine platform and navigation aid 10 moves a fixed distance D ( FIG. 2 ) (less than half the along-orbit length L (not shown) of the sonar receiver arrays 22 a-b) in an Earth-fixed coordinate system. The trigger control unit 60 is configured to control the trigger signal of the at least one transmitter 21 based on the velocity estimate from the navigation processor 40.

[0113] The sonar electronics unit 23 is configured to cause at least one transmitter (TX) 21 to ping (emit a waveform into the water) when a trigger is received from the trigger control unit 60. Each receiver (RX) array 22a-b consists of N separate elements spread across its length. The sonar electronics unit 23 is further configured to record and digitize, at an appropriate frequency and resolution, the complete time series from each receiver element of each receiver array 22a-b.

[0114] In a further embodiment, the navigation aid 10 according to the present invention includes a sound speed sensor 80 for measuring the local speed of sound in water and / or is configured to use a measure of the local speed of sound provided by the navigation processor 40 as input to the sonar processor 30.

[0115] The role of the master clock 70 is to facilitate accurate time stamping of transmission times, received data, and data from additional sensors 50 (if present).

[0116] The sonar processor 30 according to the invention comprises means and / or software for performing correlation of signals between overlapping phase centers.

[0117] In the present invention, the phase center is defined as the midpoint between the transmitter 21 and one of the receiver 22a-b elements. The overlapping phase center for a given ping is the phase center that has approximately the same location as the phase center of the previous ping.

[0118] The sonar processor 30, in accordance with one embodiment of the present invention, includes means and / or software for providing an estimate of the cross-track displacement through correlating time series from overlapping phase centers. The time delays are appropriately corrected for the three-dimensional shape and the transmitter-receiver baseline, in accordance with the present invention.

[0119] The sonar processor 30, according to one embodiment of the present invention, comprises means and / or software for providing an estimate of the platform displacement along the track by comparing the time series correlation with different displacements. A general decimal degree M of overlapping phase centers between two successive pings is defined as M=(L-2D) / d, where L is the length of the receiver array 22a-b, D is the surge displacement, and d is the receiver element spacing. The direction of the cross-track displacement can vary from nearly vertical at close ranges to nearly horizontal at long ranges from the seabed 200.

[0120] The sonar processor 30, according to one embodiment of the present invention, includes means and / or software for combining measurements from different ranges to provide information about displacement along all three axes.

[0121] In order for the navigation processor 40 to utilize the displacement measurements from the sonar processor 30, the sonar processor 30, according to one embodiment of the invention, is provided with means and / or software to find the direction of each measurement by performing further correlations and to account for these during integration.

[0122] According to yet another embodiment, the sonar processor 30 comprises means and / or software for correlating time series from the upper and lower receiver arrays, beamformed in a given azimuth direction and corrected for shifts and expansions between the receiver arrays 22a-b, to provide a calculation of the angle from the sonar transducers 20a-b to the seabed 200 in a direction from the sonar transducers 20a-b to the seabed 200.

[0123] According to yet another embodiment, the sonar processor 30 comprises means and / or software for performing the aforementioned calculations at multiple cross-trajectory ranges in order to calculate the cross-trajectory slope of the seabed 200 .

[0124] According to a further embodiment of the present invention, the sonar processor 30 comprises means and / or software for performing the above-mentioned calculations using the beamformed data in different azimuth directions to calculate the inclination along the trajectory of the seabed 200.

[0125] According to a further embodiment, the sonar processor 30 comprises means and / or software for determining the distribution of echo intensity as a function of azimuth angle.

[0126] The sonar processor 30 according to the present invention is configured to use the results of these calculations to accurately determine the direction of the displacement measurements.

[0127] According to a further embodiment of the sonar processor 30, it comprises means and / or software for estimating the accuracy of the displacement and direction measurements through further calculations using the normalized cross-correlation coefficients.

[0128] The results of the calculations (measurements), their orientation and accuracy, are used as inputs to a navigation processor 40 for further processing and use, in accordance with the present invention.

[0129] The navigation processor 40, according to one embodiment of the present invention, is built around an estimator such as a Kalman filter (KF) or an extended Kalman filter, a non-linear estimator such as an unscented Kalman filter, a particle filter, sensor fusion methods, machine learning or other similar solutions.

[0130] The estimator, in accordance with the present invention, is used to model the relationship between the navigational state (hereinafter position, orientation, and velocity), micro-navigation displacement measurements, coordinate frames, timing, and associated accuracy of the marine platform 100. According to a further embodiment of the navigation processor 40 in accordance with the present invention, the estimator is used to estimate sensor errors, such as offset and scaling errors.

[0131] The further explanation is based on the Extended Kalman Filter (EKF) as a non-limiting example of an implementation of the estimator.

[0132] In the example where the estimator is an extended Kalman filter, each element of the state vector represents the error of a particular measurement sequence. For each measurement, an equation is calculated that relates the measured parameters and their estimated standard deviations to the filter states and covariance matrix.

[0133] For each ping, multiple measurements are computed in the sonar processor 30 and used in a series of updates in the navigation processor 40, which are weighted simultaneously against the predicted filter state. Different micronavigation measurements from a single ping pair are generally valid at slightly different times. After an update, the filter state estimates and covariance matrix values ​​are predicted until the next available measurement, whether it is a new micronavigation displacement measurement or a measurement from an additional sensor 50.

[0134] The output of the navigation processor 40 is an estimate of the position, orientation, velocity and angular rate of the offshore platform 100 at any given time, as well as the variance of each of these values ​​and the covariance between each pair of values.

[0135] As described above, the sonar processor 30 measures displacement by correlating acoustic signals from successive transmissions recorded on the receiver arrays 22a-b.

[0136] The displacement component estimated from the time shift is called sway displacement (DPCA-sway) and the displacement component related to the space shift is called surge displacement (DPCA-surge). The magnitude of the displacements mentioned above has been thoroughly addressed before, but the direction of these displacement estimates was based on estimates and oversimplifications. The present invention provides accurate treatment of these directions of displacement measurements, as will be explained in detail below.

[0137] The times of interest are the two times of transmission and reception of each ping. The time of reception of the last ping is selected in accordance with one embodiment of the present invention such that the echo from the second ping provides maximum correlation with the echo from the first ping for the overlapping element or range interval of the selection or patch. The directions of interest are the directions of the two echoes at the time of their reception. The direction of each echo is a function of the orientation of both transmitters 21 at the time of transmission, the transmitter geometry, the bottom slope and scattering distribution, the receiver orientation at the time of reception and the receiver geometry.

[0138] The time delay estimates are, in accordance with the present invention, appropriately corrected for the three-dimensional geometry and the transmitter-receiver baseline.

[0139] Reference is now made to Figure 3 which shows a principle diagram of the timing of the shape and displacement measurements. In Figure 3 a diagram of the transmitter position is shown tracked by a dotted black line over two pings. The transmitter position at the time of transmission (T) and reception (R) is shown on the line. For the time of reception the receiver position is also shown (transparent). The first and second pings are shown with different filling patterns. The position of the transmitter-receiver phase centre array at the average position between the transmitter 21 and receiver 22 arrays ab is also shown using full filling. This is the effective transmitter-receiver position.

[0140] Sway displacement measurement magnitude This technique provides a measurement of the change in round trip time between signals reflected off the same patch on the seabed 200. The time delay is estimated by correlating the acoustic signals from successive transmissions. The time delay, after multiplication by the local speed of sound in the sonar processor 30, is converted to a displacement, defined as the rocking displacement measurement DeltaR_Slantrange.

[0141] Surge Displacement Measurement Magnitude This technique also provides a measure to identify the receiver array 22a-b elements that have the greatest correlation between successive transmissions. The subelement location of maximum correlation is estimated through interpolation. The number of separated elements is converted to a displacement along the trajectory, defined as the surge displacement measurement DeltaX_Body, after multiplication by half the receiver element spacing by the sonar processor 30.

[0142] Direction of sway displacement measurement The sway displacement measurement estimates the displacement towards or away from the acoustic centroid for the correlated portion of the two seafloor 200 echoes.

[0143] In accordance with the present invention, a unit vector y_Patch(n,t) points from one receiver element (n) to the centroid of its recorded seabed 200 echo at the time of reception (t).

[0144] According to one embodiment of the present invention, the direction of the sway displacement measurement is selected to approximate the direction of the sway displacement to be the average of the y_Patch estimated for the overlapping elements of two consecutive pings.

[0145] In another embodiment of the present invention, y_Patch is estimated from arbitrary elements from any ping.

[0146] According to one embodiment of the present invention, we consider that DeltaY_Patch_eff≈DeltaR_Slantrange.

[0147] For each ping, y_Patch in the present invention is a function of the position and orientation at the time of transmission, the position and orientation at the time of reception, the position of the transmitter 21, the positions of the receiver 22a-b elements, the transmitter shape, the receiver shape, the seabed slope and the seabed 200 scattering distribution.

[0148] However, the direction of y_Patch(n,t) is obtained, according to one embodiment of the present invention, by two estimates of the direction of arrival at time (t) using different reference axes. i) The angle of arrival on the receiver arrays 22a-b, which can be estimated from the time delay of reception on adjacent elements on one receiver array 22a-b, in accordance with the present invention. ii) the angle of arrival on the interference axis, which can be estimated from the time delay between reception on adjacent elements from the two receiver arrays 22a-b; It is.

[0149] Prior art solutions defined the line of sight as being broadside to the receiver array 22a-b and pointing towards the seabed 200 at a given range. This approximation corresponds to setting the angle of arrival on the receiver array 22a-b at 90 degrees and is consistent with the acoustic measurements only if the seabed 200 is both uniform and parallel to the receiver array 22a-b. While this approximation may not constitute a significant error for a narrow beam system, it can cause a significant bias when integrated, thereby affecting long-term navigation.

[0150] The sway displacement measurements relative to the line of sight are shown in FIG. 4, where the sway displacement measurements are shown on an 8 element phase center array as derived from an 8 element receiver array 22a-b having three overlapping elements.

[0151] Surge Displacement Measurement Direction It has been established before that echoes from any range will decorrelate most rapidly with displacement along the dimension in which the signal footprint has the greatest spread. Thus, echoes from a side-looking sonar with a limited field of view will be decorrelated most rapidly along the general direction of the ocean floor 200 and most slowly with motion orthogonal to the flat ocean floor 200.

[0152] Surge displacement measurements estimate the displacement across the plane of maximum correlation. This plane is sometimes called the view plane. If the surface normal can be established, this view plane is spanned by the surface normal and the line of sight (direction of the sway displacement).

[0153] According to the invention, the assessment of the visibility plane is refined by using an improved estimate of the line of sight (direction of rocking displacement). For example, in the prior art US Pat. No. 10,073,175 B2 (Pinto) it is known that by correlating elements from the upper receiver array 22a-b with elements from the lower receiver array 22a-b the visibility plane can be estimated from its intersection with the receiver plane. According to one embodiment of the invention the visibility plane is estimated from the plane spanned by the line of sight as defined in the invention and the normal vector of the seabed 200. The beams from each of the vertically displaced receiver arrays 22a-b are formed in a number of azimuth directions which are used to generate a mesh of bathymetry estimates, assigning surfaces to the estimates and obtaining surface normals. In one embodiment of the invention the distribution of echo intensity as a function of azimuth angle can be incorporated into the estimate of the normal direction of the seabed 200 scattering to further improve the estimation of the visibility plane.

[0154] 5 shows the surge displacement measurement relative to the viewing plane. It is clear that the surge displacement measurement has both orthogonal and in-plane components and that the surge displacement is not generally orthogonal to the sway displacement as previously assumed. According to one embodiment of the present invention, this is taken into account when integrating the displacement measurement with the navigation aid 10.

[0155] Direction without information / blind direction In the view plane, the sway displacement measurements are along the line of sight direction. Therefore, there is no measurement of displacement in the orthogonal direction in the view plane. Since this constitutes an unknown motion, the present invention also involves decomposing the surge displacement into components orthogonal to and along this uninformed / blind direction, after which only the components orthogonal to the uninformed / blind direction are integrated into the navigation aid 10.

[0156] Thus, the present invention utilizes micro-navigation displacement measurements in the navigation processor 40 to provide enhanced navigation data for the offshore platform 100 and therefore also enhanced control of the motion of the offshore platform 100 .

[0157] The micronavigation output 31 (FIG. 1) from the sonar processor 30 includes displacement measurements (delta positions) along the principal axes of two different coordinate systems: the receiver array 22a-b frame and the patch frame. The micronavigation output 31 further includes the complete orientation of the receiver array 22a-b frame relative to the patch frame, and the associated accuracy for all the latter quantities.

[0158] The output 31 of the sonar processor 30 also includes multiple time stamps of transmission and reception times and accounts for these during integration. The constellation of micronavigation measurements from a ping will generally be from slightly different times. Additionally, a patch angle is preferably calculated for each ping and a delta position is calculated for each pair of successive pings. A comprehensive output is needed when deriving velocity updates for the integrated navigation aid 10.

[0159] A single instance or package from output 31 may be data from either the port or starboard transducers 20a-b associated with a patch at a particular distance from the receiver array 22a-b.

[0160] In accordance with the present invention, the number of patches (per ping) is configurable and the location of the patches on the seabed 200 relative to the moving offshore platform 100 can be either static or dynamic (changing based on measurement geometry and estimated performance, including but not limited to recent measurement performance of the patches, e.g., predicted quality of a segment 201 of the seabed 200 based on static analysis of sonar data).

[0161] In accordance with the present invention, navigation processor 40 is arranged such that any number of patches may be utilized. Where computational limitations require (depending on the hardware specifications of navigation processor 40), navigation processor 40 according to further embodiments of the present invention includes a tracking device and decorrelation mechanism that allows the state in the navigation filter of navigation processor 40 to be shared by multiple micro-navigation measurements, thereby reducing the size of the navigation filter of navigation processor 40.

[0162] According to one embodiment of the present invention, the navigation filter of the navigation processor 40 is built around an estimator in the form of a linearized error-state Kalman filter (KF). In further embodiments of the navigation processor 40 according to the present invention, the navigation filter is based on higher order filters, which may be reformulated into a full-state KF without loss of generality with respect to the use of the micro-navigation output as an aid in the (integrated) navigation aid 10.

[0163] In accordance with the present invention, the estimator (KF) of the navigation processor 40 models the relationship between the navigational state (position, orientation, velocity) of the marine platform 100 and the information provided by the micro-navigation displacement measurements from the sonar processor 30.

[0164] According to a further embodiment of the present invention, an estimator (KF) of the navigation processor 40 models the relationship between the navigational state (position, orientation, velocity) of the offshore platform 100 and information provided by one or more additional sensors 50.

[0165] In accordance with the present invention, a navigation processor estimator (KF) is configured to estimate systematic errors in any measurements and calculations, including but not limited to micro-navigation displacement measurements and / or installed geometry.

[0166] According to another embodiment of the navigation processor 40 in accordance with the present invention, the estimator (KF) is configured to incorporate additional states to calibrate different system parameters, including micro-navigation scale factor error and transducer alignment error.

[0167] According to one embodiment of the present invention, navigation processor 40 comprises means and / or software for predicting between aided measurements, between different estimates and their error covariances, and for updating each time a new measurement is received.

[0168] This places stringent demands on mathematical implementation and timing in order to achieve high accuracy and full utilization of micronavigation. The present invention provides a solution for integrating micronavigation displacement measurements that accurately incorporates and utilizes available information without the approximations and assumptions of prior art methods.

[0169] According to one embodiment of the present invention, micro-navigation displacement measurements are utilized to reduce the velocity error and therefore the position error of the navigation aid device 10, which means reducing position drift. Compared to traditional velocity aid techniques (additional sensors), micro-navigation provides a higher fidelity input.

[0170] According to one embodiment of the present invention, navigation processor 40 is provided with means and / or software to achieve this. Each micro-navigation displacement measurement is linked to its own state in the estimator (Kalman filter), but the actual processing steps are the same.

[0171] In accordance with the present invention, the navigation processor 40 includes means and / or software for registering and converting the displacement measurement (delta position) to an estimator measurement, as a first step, by combining the transmission time and reception time to convert the displacement measurement in a particular coordinate system to a velocity in order to repeat a single micronavigation measurement received from the sonar processor 30. Similarly, the navigation processor 40 includes means and / or software for using the displacement accuracy either directly or indirectly by converting the displacement accuracy.

[0172] In accordance with the present invention, the representations in the different coordinate frames remain unchanged at this point, and the non-orthogonality is correctly handled when performing the lever arm compensation and estimator (KF) updates described further below.

[0173] According to one embodiment of the invention, navigation processor 40 includes means and / or software for performing micro-navigation lever arm compensation as part of the estimator (KF) measurement calculations. In another embodiment of the invention, navigation processor 40 includes means and / or software for performing micro-navigation lever arm compensation as part of the displacement measurement registration.

[0174] According to the present invention, the lever arm is composed of a static part consisting of the mechanical offset from the origin of the integrated navigation aid 10 to the transmitter 21 and multiple receiver arrays 22a-b, and a dynamic part due to the change in overlap from surge movements of the offshore platform 100.

[0175] The above lever arm calculation compensates for the effect of the lever arm on the above micronavigation displacement measurements, as well as the associated compensations for: angular velocity of the marine platform 100, intermediate rotations that occur during the time periods between different patch orientations and displacement estimates, and rotational misalignment of the receiver array 22a-b relative to the navigation frame.

[0176] The navigation processor 40 according to one embodiment of the present invention further comprises means and / or software for resolving the effect of the aforementioned lever arms in either the receiver array 22a-b frame or the patch frame for each displacement measurement.

[0177] The navigation processor 40 according to the present invention further comprises means and / or software for calculating corrections based on the estimates of the estimator (KF) observation model and the calculated accuracy in the micro-navigation displacement and orientation measurements.

[0178] According to one embodiment of the present invention, the accuracy in the micro-navigation displacement and orientation measurements is implemented in the navigation processor 40 as a function of the velocity (geographic navigation frame), the micro-navigation surge rate (receiver array 22a-b frame), and the micro-navigation sway rate (patch frame) of the navigation aid 10. According to the present invention, these are lever arms that are compensated as described above.

[0179] The navigation processor 40 according to the invention further comprises means and / or software for compensating for the non-orthogonality of the different displacement measurements, which, according to the invention, adapt the displacement measurements in the navigation frame by taking into account intermediate rotations that occur in the period between the different times of the patch orientation and the micro-navigation displacement measurements.

[0180] According to a further embodiment of the navigation processor 40, the means and / or software are further configured to take into account the rotational misalignment of the receiver array 22a-b relative to the navigation frame and / or the orientation of the acoustic estimation patch coordinate system (intensity distribution and spatial extension).

[0181] The navigation processor 40 according to the present invention further comprises means and / or software for correcting the displacement measurements in the receiver array 22a-b frame by applying the orientation of the acoustic estimation patch coordinate system.

[0182] The micro-navigation displacement and orientation measurement accuracy provided by navigation processor 40 and the output of the estimator observation model are resolved in two dimensions as patches x and patches y in the patch frame, as described above.

[0183] The estimator observation model of the estimator (KF) of navigation processor 40 thus describes the connections between the navigation states, the errors in the navigation states, and the modeled accuracy of the micronavigation displacement measurements and orientations of the patches.

[0184] According to a further embodiment of the invention, the estimator observation model for calibration is constructed by the calibration states and combinations of those states.

[0185] In one embodiment of the present invention, the errors in the navigation state are resolved in the geographic navigation frame. In this embodiment, the estimator observation model (matrix) considers the same effects of errors in the measurement derivation. More specifically, it considers the intermediate rotations that occur during the period between the different times of patch orientation and the micronavigation displacement measurement.

[0186] According to a further embodiment of the present invention, the estimator observation model also takes into account the rotational misalignment of the receiver array 22a-b relative to the navigation frame and / or the orientation of the acoustic estimation patch coordinate system (spatial extension and intensity distribution).

[0187] The micro-navigation portion of the estimator observation model (matrix) in the navigation processor 40 is parameterized around the solution of the navigation equations, such as, but not limited to, linearization, curve fitting / fitting, and the patch angles, in accordance with one embodiment of the present invention. This includes the rotation (matrix) from the receiver array 22a-b frame to the patch frame (composed of patch angles) and the derivative of this matrix with respect to the patch angles.

[0188] In another embodiment of the present invention, the above-mentioned estimator observation matrix is ​​implemented by a non-linear estimator so as to avoid the need for the above-mentioned parameterization.

[0189] According to one embodiment of the invention, the corrections are provided as inputs to a controller or control system that directly or indirectly controls the motion of the offshore platform 100. The corrections may involve estimator gains, such as Kalman filter gains if a Kalman filter is used.

[0190] According to another embodiment of the invention, the navigation processor 40 comprises means and / or software for converting the micro-navigation displacement measurements into velocity measurements applicable at pre-set / desired time intervals. This embodiment may be combined with using inertial measurement unit measurements, for example to correct or correct the time of the measurements to a better place than the pre-set / desired time interval.

[0191] According to another embodiment of the invention, navigation processor 40 comprises means and / or software for estimating expected micro-navigation displacement measurements by integrating inertial measurement unit measurements and for comparing the two.

[0192] According to another embodiment of the present invention, navigation processor 40 is provided with means and / or software for using near optimal micro-navigation displacement measurements by using additional state to "store the position and its correlation" at the start of a displacement measurement.

[0193] The latter three embodiments illustrate the various possible modifications of the present invention that can be tailored to a particular application.

[0194] According to the present invention, for the micro-navigation portion, the navigation processor 40 is provided with means and / or software for calculating an observation noise matrix based on the accuracy reported by the sonar processor 30, optionally in combination with configuration parameters such as, but not limited to, an added white noise / bias model std, motion / rotation scaled white noise / bias, range scaled white noise / bias.

[0195] As with the observation matrix, in accordance with the present invention, the observation noise matrix is ​​found by providing navigation processor 40 with means and / or software for parameterizing the observation equations and patch angles around the solution of the navigation equations. Given the parameterized model, the observation noise matrix can be found using a similarity transformation, the accuracy of the surge and sway measurements, and the patch angles.

[0196] The present invention provides a more accurate navigation aid method and apparatus 10 than prior art solutions. By providing more accurate navigation data, it also enhances the accuracy of other sensors located on the marine platform 100, such as image / visualization payload data.

[0197] The present invention provides a navigation aid method and apparatus 10 that is more robust to variations in ocean floor topography compared to prior art solutions.

[0198] The present invention also provides a navigation aid method and apparatus 10 that is more robust to non-linear offshore platform 100 dynamics, such as during turning maneuvers, as compared to prior art solutions.

[0199] The present invention provides a navigation aid method and apparatus 10 that is more robust to non-uniform distribution of scattering on the patch compared to prior art solutions.

[0200] The present invention provides a navigation aid method and apparatus that allows a higher degree of integration than previous solutions.

[0201] The above-described embodiments of the invention may be modified or combined to form new embodiments within the scope of the appended claims.

[0202] Variations The present invention may be implemented in a single-sided sonar.

[0203] The additional sensors 50 are used to provide measurements that allow the navigation processor 30 to estimate the orientation (all three degrees of freedom) of the offshore platform 100. This could be, for example, an inertial measurement unit (IMU) or a gyrocompass, although other sensors or sensor systems could also be used.

[0204] Further embodiments of the invention include using additional sensors 50 to increase the robustness and accuracy of the overall device. For example, a Doppler Velocity Log (DVL) may be integrated. A pressure sensor is another example to allow for a reduction in vertical position errors, especially if the marine platform 100 is an underwater platform.

[0205] The trigger control unit could in principle use the displacement measurement from the sonar processor 30 to generate the trigger. An additional sensor 50 is required to provide an initial velocity estimate.

[0206] The sound speed sensor may measure the speed of sound directly or through calculation from other measurements such as a Conductivity / Temperature / Depth (CTD) sensor.

[0207] Instead of the extended Kalman filter as an estimator, the navigation processor can use any nonlinear estimator such as an unscented Kalman filter or a particle filter, a machine learning algorithm such as a CNN, an optimization algorithm, RT smoothing, delayed navigation, etc. Some estimators lack some of the described features that the Kalman filter as an estimator provides and therefore may require additional operations.

[0208] Instead of using the error states, the navigation processor can use estimator states that directly represent the position, orientation, velocity, and angular rate of the marine platform 100 .

[0209] The present invention can further employ dynamic patch selection, which improves navigation performance compared to static dynamic patch selection.

Claims

1. A navigation assistance method for enhanced navigation of an offshore platform (100) on the seabed (200), A method comprising performing micronavigation displacement measurement and associated coordinate frame calculation using at least one single-sided or double-sided sonar including at least one transmitter (21) configured to transmit ping, and at least two parallel receiving arrays (22a-b), each configured substantially parallel to the direction of movement of the offshore platform (100), and receiving arrays (22a-b) configured to record echoes of ping reflected from the seabed (200), wherein The micro-navigation displacement measurement is performed along the principal axes of two different coordinate systems: a receiving array (22a-b) frame and a patch frame, the patch frame located at the acoustic centroid in the case of seabed illumination. Calculating the three-dimensional orientation of the received array (22a-b) frame with respect to the patch frame, and To calculate the accuracy of all micro-navigation displacement measurements and related coordinate frame calculations, Includes, The navigation support method is characterized by comprising: processing the micronavigation displacement measurement in the estimator observation model; modeling the relationship between the position, orientation and velocity of the ocean platform (100) in the navigation state and the micronavigation displacement measurement, coordinate frame and accuracy; and using the output of the estimator observation model to correct the navigation data of the ocean platform (100).

2. The navigation assistance method according to claim 1, wherein the output of the estimator observation model is used as an input for a controller or control system that controls the motion of the ocean platform (100) or a vessel or ship towing the ocean platform (100).

3. The navigation assistance method according to claim 1, further comprising registering the transmission and reception times of pings, calculating the patch frame angle for each ping, and calculating the delta position for each pair of consecutive pings in order to reduce velocity errors and therefore position errors.

4. The navigation support method according to claim 1, further comprising correlating elements along a trajectory in order to estimate the direction of the line of sight.

5. The navigation assistance method according to claim 1, further comprising using ping data to estimate the scattering distribution on a patch in order to estimate the direction of the line of sight.

6. The depth of the seabed (200) is estimated in multiple azimuthal directions and ranges to estimate the effective seabed (200) slope. The navigation assistance method according to claim 1, further comprising using ping data to use together an effective seabed (200) slope with a normal vector of the seabed (200) for determining the line of sight and the field of view, and a patch frame defined by the Y-axis along the line of sight, the X-axis oriented along the seabed (200), and perpendicular to them in the field of view.

7. The navigation assistance method according to claim 1, further comprising using the estimator observation model to model the relationship between the position, direction, and velocity of the navigation assistance state of the offshore platform (100) and the measurements and / or state from the additional sensor (50).

8. Navigation assistance method according to claim 1, further comprising using the estimator observation model to estimate systematic errors in the measurement and calculation, including but not limited to the micronavigation displacement measurement and / or the installed shape and / or the state from the additional sensor (50).

9. The navigation support method according to claim 1, further comprising using a Kalman filter or an extended Kalman filter as the estimator observation model.

10. Navigation support method according to claim 1, further comprising predicting the estimation of the estimator observation model and its error covariance between micronavigation displacement measurements and associated coordinate frame measurements, and updating a different estimation and its error covariance each time a new micronavigation displacement measurement and associated coordinate frame measurement are registered.

11. The navigation support method according to claim 1, further comprising converting the micronavigation displacement measurement into a calculation of an estimator observation model by combining the transmission time and reception time to convert the displacement into velocity.

12. The navigation support method according to claim 1, further comprising using displacement accuracy by directly or indirectly converting the displacement accuracy into velocity accuracy in combination with transmission time and reception time.

13. The navigation assistance method according to claim 1, further comprising performing micronavigation lever arm compensation as part of the estimator observation model calculation.

14. The navigation support method according to claim 13, further comprising calculating the lever arm compensation using a static portion from the mechanical offset from the origin of the navigation support device to the sonar transmitter (21) and the plurality of receiver arrays (22a-b), and a dynamic portion due to changes in overlap caused by the surge motion of the marine platform (100).

15. Navigation assistance method according to any one of claims 1 to 6, further comprising calculating a three-dimensional rotation between the receiver array (22a-b) frame and the patch frame by rotating the patch frame relative to the receiver array (22a-b) frame during the transmission and reception times of two consecutive pings.

16. Navigation assistance method according to claim 15, further comprising using the estimator observation model to describe the connections between navigation states of the ocean platform (100), the errors of the navigation states of the ocean platform (100), and the accuracy of the micronavigation displacement measurement and the rotation of the patch frame relative to the receiver array (22a-b) frame.

17. The navigation support method according to claim 16, further comprising calibrating the device parameters based on the scaling error and transducer alignment error of the estimator observation model by incorporating additional states into the estimator observation model.

18. Navigation assistance method according to claim 12, further comprising calculating an observation noise matrix based on a combination of constituent parameters such as a white noise / bias model standard, motion / rotation scaled white noise / bias, range scaled white noise / bias, added by parameterizing the solution of the navigation equation and the observation equation around the patch angle, but not limited to the calculated accuracy.

19. Converting the aforementioned micro-navigation displacement measurement into a velocity measurement applicable to a preset time interval or a desired time interval, By integrating inertial measurement unit measurements, the expected micronavigation displacement measurements can be estimated and compared with the said micronavigation displacement measurements, or To store the position and its correlation from the start to the completion of the micronavigation displacement measurement, additional states in the estimator observation model are used. Perform one or more of the following: The navigation support method according to claim 11, further comprising:

20. A navigation support device (10) for enhanced navigation of an offshore platform (100) on the seabed (200), The navigation support device (10) includes at least one transmitter (21) configured to transmit ping, and at least one single-sided or double-sided sonar, which includes at least two parallel receiver arrays (22a-b) each configured substantially parallel to the direction of movement of the offshore platform (100), and the receiving array (22a-b) configured to record echoes of ping reflected from the seabed (200). The sonar is configured to perform micronavigation displacement measurement and associated coordinate frame calculations. The navigation device (10) includes a navigation processor (40), The navigation support device (10) is configured to perform the micro-navigation displacement measurement along the principal axes of two different coordinate frames in the form of a receiving array (22a-b) frame and a patch frame, the patch frame being positioned at the acoustic centroid in the case of seabed illumination, The navigation processor (40) includes means and / or software for calculating the three-dimensional orientation of the receiver array (22a-b) frames relative to the patch frame, and for calculating the accuracy of all micronavigation displacement measurements and associated coordinate frame calculations. The navigation processor (40) processes micronavigation displacement measurements and includes an estimator observation model that models the relationship between the position, bearing, and velocity of the ocean platform (100) in its navigation state and the micronavigation displacement measurements, coordinate frame, and accuracy. The output of the estimator observation model is used to correct the navigation data of the ocean platform (100). Navigation support device (10) characterized by the following:

21. The calculated correction is provided to a controller or control system that controls the motion of the offshore platform (100) or a vessel towing the offshore platform (100) or the motion of the vessel, according to claim 20, the navigation support device (10).

22. Navigation support device (10) according to claim 20, further comprising a sonar processor (30) configured to perform the micronavigation displacement measurement between sonar transmission and coordinate frames for each such measurement.

23. The navigation support device (10) according to claim 20, further comprising a trigger control unit (60) configured to control a trigger signal to at least one transmitter (21) each time a fixed distance (D) is traveled in any Earth-fixed coordinate system, based on a velocity estimate from a navigation processor (40).

24. The sonar processor (30) is Performing the correlation of signals between overlapping phase centers, By correlating the time series from the overlapping phase centers, the estimation of trajectory transverse displacement is provided. By comparing the correlation of time series with different displacements, we can provide an estimate of the platform displacement along the orbit. Furthermore, by performing correlation of micronavigation displacement measurements, the direction of each micronavigation displacement measurement can be found and addressed during integration. Correlating time series from receiver arrays (22a-b) that are beamformed in a predetermined azimuthal direction or delayed with respect to a predetermined azimuthal direction, and corrected for shifts and expansions between receiver arrays (22a-b) that provide the calculation of the angle from sonar transducers (20a-b) to the seabed (200) in that direction, To calculate the trans-orbital inclination of the seabed (200), calculations are performed across multiple trans-orbital ranges. To calculate the inclination along the orbit of the seabed (200), calculations are performed using beamformed data in different azimuth directions. Determining the distribution of echo intensity as a function of azimuth angle, and / or, Using normalized cross-correlation coefficients, estimate the accuracy of micronavigation displacement measurements and associated coordinate frame measurements through further calculations. A means and / or software for one or more of the following: Navigation support device (10) according to any one of claims 22 to 23.

25. Navigation support device (10) according to claim 20, wherein the estimator observation model is configured to model the relationship between the position, direction, and velocity of the navigation state of the ocean platform (100) and, but not limited to, measurements and / or states from additional sensors (50), such as an inertial measurement unit or a gyrocompass.

26. The aforementioned navigation processor (40) By combining the transmission time and reception time to convert the micronavigation displacement into velocity, the micronavigation displacement measurement is registered and converted to the estimator measurement. Converting the displacement accuracy of a combination of transmission and reception times to velocity accuracy, either directly or indirectly, thereby converting the micro-navigation displacement accuracy. Performing micro-navigation lever arm compensation as part of the estimator observation model calculation, The non-orthogonality between the received array (22a-b) frame and the patch frame is corrected by rotating the patch frame with respect to the received array (22a-b) frame between the transmission and reception times of two consecutive pings. Means and / or software are provided for one or more of the following: Navigation support device (10) according to claim 20.

27. The navigation processor (40) Converting the aforementioned micro-navigation displacement measurement into a velocity measurement applicable at a preset time interval or a desired time interval, By integrating inertial measurement unit measurements, estimate the expected micronavigation displacement measurements, compare them with the micronavigation displacement measurements, and / or, To store the position and its correlation from the start to the completion of the micronavigation displacement measurement, additional states in the estimator observation model are used. Means and / or software are provided for one or more of the following: Navigation support device (10) according to claim 20.

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