A SYSTEM AND METHOD FOR DETECTING AND DELINEATING AN OBJECT THAT IS AT LEAST PARTIALLY BURIED IN THE SEABED

Abstract

The disclosure relates to a system for detection and delineation of an object that is at least partly buried in seabed, the system comprising: a marine vehicle (1,10); a controlled electric dipole source (3) mounted on the marine vehicle; a first receiver electrode pair (4) comprising vertical receiver electrodes (4a, 4b) mounted on the marine vehicle, the vertical receiver electrodes (4a4b) separated from one another in the vertical direction of the AUV (1); a 3 axes magnetometer assembly; wherein the receiver pair (4) is configured to measure electric field and the 3-axes magnetometer assembly is configured to measure magnetic field. The disclosure further relates to a method of detection and delineation of an object that is at least partly buried in seabed.

Description

1 / 18 A SYSTEM AND METHOD FOR DETECTING AND DELINEATING AN OBJECT THAT IS AT LEAST PARTIALLY BURIED IN THE SEABED Technical field

[001] The present disclosure relates to a system for detecting and delineating an object that is at least partially buried in the seabed and to a method for detecting and delineating an object that is at least partially buried in the seabed. More specifically, the disclosure relates to a system for detecting and delineating an object that is at least partially buried in the seabed and to a method for detecting and delineating an object that is at least partially buried in the seabed, as defined in the introductory parts of claim 1 and claim 9. Technical background

[002] Scanning for buried conductive objects is an important underwater research task before establishing any installation on the seabed. It is vital to know if there are any unwanted obstacles that need to be removed before any exploration of the area of ​​interest. Traditionally, passive magnetometer and gradiometer sensors are used to detect magnetized metallic objects, such as Unexploded Ordnance (UXO). These sensors are usually mounted on structures that are towed close to the seabed along lines separated by only a few meters. This method is widely used, but time-consuming.

[003] Active Controlled Source Electromagnetic (CSEM) technologies for underwater environments have also been developed for detecting buried conductive objects, such as sea mines and UXOs. A CSEM method for detecting and locating buried metallic objects was developed in 2000 at the Swedish Defence Research Agency (FOI). The method consisted of Petition 870240060720, dated 07 / 18 / 2024, pp. 114 / 158 2 / 18 a horizontal electric dipole source in combination with a vertical electrode receiver pair in the middle of the source. Some examples of the state of the art include: Johan Mattsson and Peter Sigray, Electromagnetic Sea-Mine Detection, FOA-R—00-01547-409—SE, ISSN 1104-9154, 2000; and Lennart Crona, Tim Fristedt, Johan Mattsson and Peter Sigray, Active EM Marine Tests for Sea Mine Detection, FOA-R--00-01757-313—SE, ISSN 1104-9154, 2000. This method has also been combined with acoustic measurements from an SBP sensor to determine a higher resolution structure of the buried object.

[004] A similar CSEM method for locating underwater metallic objects is disclosed in patents WO 2006 / 134329 A2 and US 8,055,193 B2.

[005] WO 2006 / 134329 A2 discloses an underwater remote sensing system comprising a transmitter for transmitting an electromagnetic signal, a receiver for receiving an electromagnetic signal reflected from an object, and means of determination for determining the location of the object, wherein at least one of the transmitter and receiver is underwater. The means of determination may be operable to determine the location of the object using signals received at three or more receiver positions. To do this, three or more receiving antennas may be provided. Alternatively, a single receiving antenna may be provided and moved between three or more different measurement locations.

[006] US 8,055,193 B2 discloses an underwater remote sensing system comprising a transmitter for transmitting an electromagnetic signal, a receiver for receiving an electromagnetic signal reflected from an object, and means of determination for determining the location of the object, wherein at least one of the transmitter and receiver is underwater. The means of determination may be operable to determine the location of the object using signals received at three or more receiver positions. To do Petition 870240060720, dated 07 / 18 / 2024, pp. 115 / 158 3 / 18 In this case, three or more receiving antennas can be provided. Alternatively, a single receiving antenna can be provided and moved between three or more different measurement locations.

[007] However, the physics described in WO 2006 / 134329 A2 and US 8,055,193 B2 relates to the detection of a reflected wave at transmitted frequencies of 1-3 MHz. This type of physics does not work in seawater with the typical conductivity of the oceans. Energy with frequencies in this region would propagate only a few meters in the water and would not be reflected from an object as a reflected wave, as in airborne radar applications or with underwater acoustic sonars. The relevant physics is correctly described in a diffusion-like manner, where much lower frequencies must be used for a practical underwater CSEM sensor system for detecting and locating buried metallic objects.

[008] The conventional approach to interpreting electromagnetic (EM) data from towed seismic cables is based on 2.5-D and / or 3-D inversions of the observed data in resistivity models of the underground formations. However, rigorous 3-D and even 2.5-D inversions require large amounts of computational time and power. The synthetic aperture (SA) method is a key technique in remote sensing using radio frequency signals. An example of this method is disclosed in Rapid Imaging of Towed Streamer EM Data Using the Optimal Synthetic Aperture Method, Michael S. Zhdanov, Daeung Yoon, and Johan Mattsson, IEEE GEOSCIENCE AND REMOTE SENSING LETTERS, VOL. 14, NO. 2, FEBRUARY 2017. A recently proposed CSEM method for tracking buried pipelines is described in patent application NO20211242. This method is based on having a dipole source of electric current implemented in an Autonomous Underwater Vehicle (AUV). The source Petition 870240060720, dated 07 / 18 / 2024, pp. 116 / 158 4 / 18 transmits an electric current to the seawater at appropriate frequencies, and the resulting magnetic field is measured by magnetometers mounted on the same AUV. The magnetic field is then used in a reversal algorithm that predicts the position of the nearest part of the tubing. Summary

[009] According to a first aspect, a system is provided for detecting and delineating an object that is at least partially buried in the seabed, the system comprising: a marine vehicle; a controlled electric dipole source mounted on the marine vehicle; a first pair of receiving electrodes comprising vertical receiving electrodes mounted on the marine vehicle, the vertical receiving electrodes separated from each other in the vertical direction of the AUV; a 3-axis magnetometer assembly; wherein the receiving pair is configured to measure the electric field and the 3-axis magnetometer assembly is configured to measure the magnetic field.

[010] According to some embodiments, the sea vehicle is an Autonomous Underwater Vehicle, AUV, having a hull; the AUV further comprises: a second receiver pair comprising in-line receiver electrodes mounted on the hull of the hull-mounted AUV, the in-line receiver electrodes being separated from each other in the longitudinal direction of the sea vehicle; and a third receiver pair comprising cross-line receiver electrodes mounted on the hull of the hull-mounted AUV, the receiver electrodes being separated from each other in the cross-line direction of the AUV; wherein the second and third receiver pairs are configured to measure the electric field.

[011] According to some embodiments, the controlled electric dipole source comprises at least two metal electrode plates mounted at the first end and at the second end of the AUV hull. Petition 870240060720, dated 07 / 18 / 2024, pp. 117 / 158 5 / 18

[012] According to some embodiments, the system comprises an Unmanned Surface Vehicle, USV, having a hull; the sea vehicle is a cable attached behind the USV via a tow cable, the cable being attached to the USV via a tow cable.

[013] According to some embodiments, the controlled electric dipole source operates in the frequency range between 1 and 1000 Hz.

[014] According to some embodiments, the system additionally comprises a processor that is configured to use measurements from at least one pair of receiving electrodes and a 3-axis magnetometer mount to create a conductivity structure of the buried object.

[015] According to some embodiments, a position of the buried object relative to the sea vehicle is estimated from data measured with at least one pair of receiving electrodes and a 3-axis magnetometer mount.

[016] According to a second aspect, a method is provided for detecting and delineating an object that is at least partially buried in the seabed, the method comprising the steps of: transmitting electromagnetic energy from a controlled electric dipole source mounted on the hull of an Autonomous Underwater Vehicle or on a cable towed by an Unmanned Surface Vehicle; arranging a first pair of receiving electrodes comprising vertical receiving electrodes mounted on the hull of the AUV or within a cable towed behind the USV, the vertical receiving electrodes being separated from each other in the vertical direction of the AUV; measuring the electric field with the receiving electrodes; measuring the magnetic field with at least one 3-axis magnetometer mount mounted on the hull of the AUV or within a cable towed behind the USV; processing measured data with a processor located onboard the AUV or USV, the processor adapted Petition 870240060720, dated 07 / 18 / 2024, pp. 118 / 158 6 / 18 to increase the sensitivity of the measured data when using the Aperture method. Synthetic.

[017] According to some embodiments, the method comprises the steps: arranging a second receiver pair, the method comprises in-line receiver electrodes mounted on the hull of the AUV, the receiver electrodes are separated from each other in the longitudinal direction of the AUV or USV; and arranging a third receiver pair comprising cross-line receiver electrodes mounted on the hull of the AUV, the receiver electrodes are separated from each other in the cross-line direction of the AUV; measuring the electric field with the receiver pair electrodes mounted on the hull of the AUV.

[018] According to some embodiments, the electromagnetic energy transmitted by the controlled electric dipole source contains discrete frequencies between 1 and 1000 Hz.

[019] According to some embodiments, the processor, when using the Synthetic Aperture method, normalizes the measured data with a background field and combines them with optimized weights.

[020] According to some modalities, the Opening method Synthetic is given as; A(w) =(Ç'..... where dA = Enw, dB = ENbw μμ'1 • E:''\ : , ENb = E^J μύ(' . • E^\ : , W = • E^J en = \E(tL> U / '' the matrices ENe ENb containing magnetic or electric field values Petition 870240060720, dated 07 / 18 / 2024, pp. 119 / 158 7 / 18 for controlled electric dipole source positions 1,..., J and all receiver positions 1,..., L; w1 ... Wj denotes the weights.

[021] According to some modalities, optimize the weights by minimizing the following function: P(w) = \\D — A(w)||2+ a||dw||2o vector D is a projected Synthetic Opening; a is a regularization parameter; and dw are consecutive changes of the weights Wj.

[022] According to some methods, obtain the conductivity structure of the buried object by feeding the processed data into a trained Convolutional Neural Network.

[023] The effects and attributes of the second and third aspects are, to a large extent, analogous to those described above in relation to the first aspect. The modalities mentioned in relation to the first aspect are largely compatible with the second and third aspects.

[024] The present disclosure will become evident from the detailed description given below. The detailed description and specific examples disclose preferred modes of disclosure for illustrative purposes only. Those skilled in the art understand, based on the guidance in the detailed description, that changes and modifications may be made within the scope of the disclosure.

[025] Therefore, it should be understood that the invention disclosed in this disclosure is not limited to the particular component parts of the described device or steps of the described methods, since such device and method may vary. It should also be understood that the terminology used in the present invention is intended for the purpose of describing only particular embodiments and is not intended to be limiting. It should be noted that, as used in the descriptive report and appended claims, the articles "a," "an," "the," "referred to," and "referred to" are intended to mean that there is one or more of the elements, Petition 870240060720, dated 07 / 18 / 2024, pp. 120 / 158 8 / 18 unless the context explicitly indicates otherwise. Thus, for example, reference to a unit or the unit may include multiple devices and the like. Additionally, words comprising, including, containing, and similar formulations do not exclude other elements or steps. Brief description of the drawings

[026] The above objects, as well as additional objects, attributes and advantages of the present disclosure, will be more fully appreciated by reference to the following detailed illustrative and non-limiting description of exemplary embodiments of the present disclosure, when taken together with the accompanying drawings.

[027] Figure 1 shows an electromagnetic data acquisition system using an Autonomous Underwater Vehicle (AUV).

[028] Figure 2 shows an electromagnetic data acquisition system using an Unmanned Surface Vehicle (USV).

[029] Figure 3 shows the source switching sequence for detecting buried objects.

[030] Figure 4 shows a vertical cross-section of the geometry of the data acquisition model.

[031] Figures 5a, 5b, 6a, 6b show the detection of a buried object using the Synthetic Aperture Method processing method in the computed vertical electric field Eze in the horizontal magnetic field Bx. Detailed description

[032] The present disclosure will now be described with reference to the accompanying drawings, which show preferred exemplary embodiments of the disclosure. The disclosure may, however, be embodied in other ways and should not be interpreted as being limited to the embodiments Petition 870240060720, dated 07 / 18 / 2024, pp. 121 / 158 9 / 18 disclosed in the present invention. The disclosed embodiments are provided to fully convey the scope of the disclosure to those skilled in the art.

[033] The following embodiments describe a maritime vehicle, in one embodiment, an Autonomous Underwater Vehicle and, in a second embodiment, an Unmanned Surface Vehicle.

[034] Figure 1 shows an electromagnetic data acquisition system using an Autonomous Underwater Vehicle, hereinafter referred to as AUV. The system comprises at least one AUV 1 having a hull with a first end and a second end, the AUV 1 is equipped with at least one controlled electric dipole source (CSEM) 3 comprising one or more metal electrode plates 3a, 3b mounted on the hull of the AUV 1 source. In this embodiment, the electrodes are mounted on the outside of the hull, on the underside of the hull.

[035] The AUV 1 further comprises a sensor arrangement comprising the first 4, second 5, third pairs of receiving electrodes 6 and at least one 3-axis magnetometer assembly 7. The first pair of receiving electrodes 4 comprises vertical receiving electrodes 4a, 4b mounted on the hull of the AUV 1, the receiving electrodes 4a, 4b being separated from each other in the vertical direction of the AUV 1. The second receiving pair 5 comprises in-line receiving electrodes 5a, 5b mounted on the hull of the AUV 1, the receiving electrodes 5a, 5b being separated from each other in the longitudinal direction of the AUV 1. The third receiving pair 6 comprises cross-line receiving electrodes 6a, 6b mounted on the hull of the AUV 1, the receiving electrodes 6a, 6b being separated from each other in the cross-line direction of the AUV 1. The AUV1 further comprises a 3-axis magnetometer assembly, the magnetometer assembly of 3 axles are mounted inside the hull of the AUV 1.The first, second, and third receptor pairs are... Petition 870240060720, dated 07 / 18 / 2024, pp. 122 / 158 The 10 / 18 array is configured to measure the electric field, and the 3-axis magnetometer mount is configured to measure the magnetic field.

[036] Figure 2 shows another embodiment of the invention where electromagnetic data are acquired using an Unmanned Surface Vehicle (USV). Figure 2 shows a USV 8 towing a cable 10, the cable comprising a controlled electric dipole source 3, an in-line receiving electrode 4 and a 3-axis magnetometer mount 7. The cable 10 is connected to a depressor 9, which is configured to control the towing depth of the cable 10. The cable 10 and the depressor 9 are attached to the USV 8 with a towing cable 11. It is possible to combine the embodiment shown in Figure 1 and the embodiment shown in Figure 2. The cable may additionally be equipped with pairs of receiving electrodes 5 and 6.

[037] The receiving electrodes and magnetometers are electrically connected to an electronic measuring unit, and the source is electrically connected to an electronic source. Both the source electronics and the measuring electronics are confined within the onboard AUV 1 or USV 8. The source and the measuring electronics are galvanically isolated from each other. The power required for the operation of the source and the receivers is drawn from a battery onboard the AUV or USV.

[038] The emission sequences of the controlled electric dipole source 3 are designed to have frequency spectra with frequencies sensitive to buried objects. This means that the transmitted electric current creates magnetic and electric fields that will change in amplitude and phase at these frequencies when the emission sequence of the controlled electric dipole source 3 is passing near the buried object. A source sequence is created by switching the emission polarity between positive and negative. An example is shown in Figure 3. In this case, the switching sequence is 2 seconds long, Petition 870240060720, dated 07 / 18 / 2024, pp. 123 / 158 11 / 18 top panel, and contains distinct frequency peaks between 2 and 15 Hz, amplitude frequency spectrum on the bottom panel.

[039] When acquiring electromagnetic data, the AUV 1 and / or USV 8 source is prepared to run in a line configuration, in which the AUV 1 and / or USV 8 source is operated to move along suitably defined survey lines covering an area of ​​interest.

[040] The survey lines are parallel to the receiving electrodes in line 5a, 5b (x direction), so that the second pair of receiving electrodes in line 5a, 5b measures the electric field parallel to survey lines 1. The first receiving pair 4a, 4b is configured to measure the vertical components of the electric field. The third receiving pair 6a, 6b is configured to measure the y components of the electric field. The system may additionally comprise a processor, which is configured to use measurements from the receivers to generate a conductivity map / structure of the conductive bodies in the area of ​​interest.

[041] Electric and magnetic fields are measured continuously at a sampling rate < 300 Hz when AUV 1 or USV 8 moves along a survey line. Electromagnetic data measured after a survey line is completed are decomposed with source sequences in the frequency domain at frequency peaks to obtain frequency responses at those frequencies. Frequency responses will vary with conductivity in the marine environment. Consequently, if a highly conductive object is within the sensitivity range of the controlled electric dipole source emission, the frequency responses will change significantly.

[042] It is crucial that the electrical and magnetic data be sensitive enough for the buried object of interest to be able to detect and locate it accurately. The sensitivity of detection also imposes restrictions on Petition 870240060720, dated 07 / 18 / 2024, pp. 124 / 158 12 / 18 spatial sampling frequency along and between the survey lines. Height above the seabed is also a critical parameter for a successful survey. Low sensitivity to buried objects forces the controlled electric dipole source emission to remain close to the seabed.

[043] An efficient method that allows for significantly higher sensitivity in CSEM data without a decrease in the signal-to-noise ratio is the synthetic aperture method, hereinafter referred to as SA. In this method, the acquired electromagnetic data are normalized with a background field and combined with optimized weights. In essence, an SA expression is derived and mathematically stated as: A(w) = 42)4» where dA= ENw, dB= ENbw ENb= ^W(L> ?Nb'í) ?Nb(L) [W1, W2, , Wj]T.

[044] The matrices ENe ENb contain normalized magnetic or electric field values ​​for all positions of the source 1,..., J and all positions of the receiver 1,..., L. The weights are denoted as W'... Wj.

[045] The synthetic aperture along all receiver positions is called directionless SA when the weights Wj are all equal to 1. This is the data with original sensitivity. To increase sensitivity, the weights are optimized by minimizing the following features: P(w) = \\D — A(w)||2+ a||dw||2.

[046] Vector D is a projected SA, with a regularization parameter and Petition 870240060720, dated 07 / 18 / 2024, pp. 125 / 158 13 / 18 dw consecutive weight changes Wj.

[047] An example using the SA method and a demonstration of the increased sensitivity are shown in the sections below.

[048] The feasibility of the invention is demonstrated here in a modeling case where the detection ranges for a representative buried conductive object are computed and plotted. The SA method, explained above, is used to enhance sensitivity and thus allow for a sparser set of search lines.

[049] The modeling case has a one-dimensional environment as shown in Figure 4. In Figure 4, a highly conductive object 12 of size 1.2x0.3x0.3 is buried 1.5 m below the seabed 13 at x = y = 0. The conductivity of the body is representative of iron. An electric dipole source in the x direction, with an intensity of 500 Am and a frequency of 10 Hz, runs along a set of survey lines 14 at a height of 10 m above the seabed 13. The vertical electric field component Ez and the horizontal magnetic field component Bx are calculated at the same height, but with a deviation from the source of 3 m. In a practical measurement setup, the source and receivers would be on the same AUV 1 or towed behind the USV 8 as described above. It should also be mentioned that both the electric and magnetic vector components are measurable in reality, although they are not shown here.

[050] Figures 5a, 5b, 6a, 6b show the detection of a buried iron object using SA processing in the computed vertical electric field Eze in the horizontal magnetic field Bx. The number of search lines is 14, and there are 17, separated by 4 m. They are marked as dashed horizontal lines in Figures 5 and 6. The Eze Bx field components are sampled every meter along each of the lines. This dense sampling and Petition 870240060720, dated 07 / 18 / 2024, pages 126 / 158 14 / 18 dense line sets are used to make the resulting detection results as accurate as possible. From the results, one can conclude how dense the lines need to be.

[051] The Eze Bx field components are normalized with representative background fields, i.e., with the Eze Bx fields outside the sensitivity range for the buried object. The resulting normalized quantities are then used in the expression for the SA. Thus, an SA vector is formalized for each of the field components and for each of the search lines. The results are visualized as discrete grayscale graphs in Figures 5 and 6. Figures 5a and 6a show graphs with weights equal to one, i.e., without direction, and Figures 5b and 6b show graphs of optimized SA where the weights were calculated by minimizing the objective function described above.

[052] It can be observed that the sensitivity intensity generally increases with optimized weights. It is increased by a factor of 3-4 when directly above the buried object. This enables an increase in the height of the CSEM system above the seabed. Additionally, it can also be seen that the horizontal sensitivity is increased in both x and y directions for the Bx in Figure 6b. In particular, the sensitivity range is doubled in both directions.

[053] It can be noted that the magnetic field component Bx is the most sensitive to a buried object after optimizing the weights in the SA expression. It would be possible to have a line separation between 15-20 m when the optimized SA was applied to the Bx data. It would probably also be possible to increase the height above the seabed from 10 m to something higher and still be able to detect the buried object.

[054] The first aspect of this disclosure shows a system for detecting and outlining an object that is at least partially Petition 870240060720, dated 07 / 18 / 2024, pages 127 / 158 15 / 18 buried in the seabed, the system comprising: a tenth aspect marine vehicle,10; a controlled electric dipole source 3 mounted on the marine vehicle; a first pair of receiving electrodes 4 comprising vertical receiving electrodes 4a,4b mounted on the marine vehicle, the vertical receiving electrodes 4a4b separated from each other in the vertical direction of the AUV 1; a 3-axis magnetometer assembly; wherein the receiving pair 4 is configured to measure the electric field and the 3-axis magnetometer assembly is configured to measure the magnetic field.

[055] The maritime vehicle is an Autonomous Underwater Vehicle 1, AUV, having a hull; the AUV further comprises: a second receiver pair 5 comprising in-line receiver electrodes 5a,5b mounted on the hull of the hull-mounted AUV 1, the in-line receiver electrodes 5a,5b being separated from each other in the longitudinal direction of the maritime vehicle 1,10; and a third receiver pair 6 comprising cross-line receiver electrodes 6a,6b mounted on the hull of the hull-mounted AUV 1, the receiver electrodes 6a,6b being separated from each other in the cross-line direction of the AUV 1; wherein the second and third receiver pairs are configured to measure the electric field.

[056] The controlled electric dipole source comprises at least two metal electrode plates 3a,3b mounted at the first end and at the second end of the AUV hull.

[057] The system comprises an Unmanned Surface Vehicle 8, USV, having a hull; the sea vehicle is a cable 10 fixed behind the USV 8 via a towing cable 11, the cable 10 being fixed to the USV via a towing cable 11.

[058] The second aspect of this disclosure shows a system for detecting an object that is at least partially buried on the seabed, the system comprising: Unmanned Surface Vehicle USV o Petition 870240060720, dated 07 / 18 / 2024, pages 128 / 158 16 / 18 aspect having a hull; A cable 10 fixed behind the USV 8 via a tow cable 11, the cable 10 fixed to the USV via a tow cable 11; the cable comprising a controlled electric dipole source 3; at least one pair of receiving electrodes 4; at least one 3-axis magnetometer assembly; wherein the pair of receiving electrodes is configured to measure the electric field and the 3-axis magnetometer assembly is configured to measure the magnetic field.

[059] The controlled electric dipole source operates in the frequency range between 1 and 1000 Hz.

[060] The system further comprises a processor that is configured to use measurements from at least one pair of receiving electrodes and a 3-axis magnetometer mount to create a conductivity structure of the buried object.

[061] The position of the buried object relative to the sea vehicle 1,10 is estimated from data measured with at least one pair of receiving electrodes and the 3-axis magnetometer mount.

[062] The second aspect of this disclosure shows a method for detecting and delineating an object that is at least partially buried in the seabed, the method comprising the steps of: transmitting electromagnetic energy from a controlled electric dipole source, the first aspect mounted on the hull of an Autonomous Underwater Vehicle 1 or on a cable 10 towed behind an Unmanned Surface Vehicle 8; arranging a first pair of receiving electrodes 4 comprising vertical receiving electrodes 4a, 4b mounted on the hull of the AUV 1 or within a cable 10 towed behind the USV 8, the vertical receiving electrodes 4a, 4b being separated from each other in the vertical direction of the AUV 1; measuring the electric field with the receiving electrodes 4; measuring the magnetic field with at least one magnetometer assembly. Petition 870240060720, dated 07 / 18 / 2024, pp. 129 / 158 17 / 18 3-axis 7 mounted on the hull of AUV 1 or inside a cable 10 towed behind USV 8; process measured data with a processor located onboard AUV 1 or USV 8, the processor adapted to increase the sensitivity of the measured data when using the Synthetic Aperture method.

[063] Arranging a second receiver pair 5, the method comprises line receiver electrodes 5a,5b mounted on the hull of the hull-type AUV 1, the receiver electrodes 5a5b are separated from each other in the longitudinal direction of the AUV or USV 8; and arranging a third receiver pair 6 comprising cross-line receiver electrodes 6a,6b mounted on the hull of the hull-type AUV 1, the receiver electrodes 6a6b are separated from each other in the cross-line direction of the AUV 1; measuring the electric field with receiver pair electrodes 4a,4b,5a,5b,6a,6b mounted on the hull of AUV 1.

[064] The electromagnetic energy transmitted by the controlled electric dipole source contains discrete frequencies between 1 and 1000 Hz.

[065] The processor, when using the Synthetic Aperture method, normalizes the measured data with a background field and combines them with optimized weights.

[066] The Synthetic Opening method is given as; A(w) = d® d®lTd®.....d? in what En= .N(L) dA= ENw, ... h:1'\ ·· E / m / dB= ENbw I, ENb= E^ (1)ENb(17) [|V,, W2.....IV;]T. the matrices ENe ENb containing magnetic or electric field values ​​for controlled electric dipole source positions 1,..., J and all positions of Petition 870240060720, dated 07 / 18 / 2024, pp. 130 / 158 18 / 18 receiver 1,..., L; w1 ... Wj denotes the weights.

[067] Optimize the weights by minimizing the following function: P(w) = \\D — A(w)||2+ a||dw||2o vector D is a projected Synthetic Aperture; a is a regularization parameter; and dw are consecutive changes of the weights Wj. Obtain the conductivity structure of the buried object by feeding the processed data into a trained Convolutional Neural Network.

[068] A person skilled in the art understands that the present disclosure is not limited to the preferred embodiments described above. A person skilled in the art further understands that modifications and variations are possible within the scope of the appended claims. Additionally, variations in the disclosed embodiments may be understood and effected by a person skilled in the art in the practice of the claimed disclosure, based on a study of the drawings, the disclosure and the appended claims. Petition 870240060720, dated 07 / 18 / 2024, pp. 131 / 158

Claims

1 / 5 CLAIMS 1. System for detecting and delineating an object, the system comprising: a marine vehicle (1, 10), a controlled low-frequency electric dipole source (3) mounted on the marine vehicle, and a 3-axis magnetometer mount (7), the system characterized in that the 3-axis magnetometer mount (7) is configured to measure magnetic field.

2. System according to claim 1, characterized in that the low-frequency dipole source operates in the range 0 - 99 Hz, or more advantageously between 2 - 15 Hz, or most advantageously at 10 Hz.

3. System according to claim 1 or 2, characterized in that the object is at least partially buried in the seabed.

4. System according to claim 1, characterized in that the sea vehicle is an Autonomous Underwater Vehicle (1), AUV, having a hull, and the AUV further comprises: a first pair of receiving electrodes (4) comprising vertical receiving electrodes (4a, 4b) mounted on the sea vehicle, the vertical receiving electrodes (4a, 4b) separated from each other in the vertical direction of the AUV (1), the first pair of receivers (4) is configured to measure electric field.

5. System according to claim 4, characterized in that the AUV further comprises: a second receiver pair (5) comprising in-line receiver electrodes (5a, 5b) mounted on the hull of the AUV (1), the in-line receiver electrodes (5a, 5b) being separated from each other in the longitudinal direction of the sea vehicle (1, 10), and a third receiver pair (6) comprising cross-line receiver electrodes (6a, 6b) mounted on the hull of the AUV (1), the receiver electrodes (6a, 6b) being separated from each other in the cross-line direction of the AUV (1), wherein the second and third receiver pairs are configured to measure electric field.

6. System according to any one of claims 1 to 5, characterized in that the controlled low-frequency electric dipole source comprises at least two metal electrode plates (3a, 3b) mounted at the first end and the second end of the AUV hull.

7. System according to claim 4, characterized in that it further comprises an Unmanned Surface Vehicle (8), USV, having a hull, and the sea vehicle is a cable (10) fixed behind the USV (8) via a tow line (11), the cable being fixed to the USV via a tow line (11).

8. System, according to any one of claims 4 to 7, characterized in that the system further comprises a processor that is configured to use measurements from at least one pair of receiving electrodes and / or a 3-axis magnetometer assembly to create a conductivity structure of the buried object.

9. System, according to any one of claims 4 to 8, characterized in that a position of the object at least partially buried in relation to the sea vehicle (1, 10) is estimated from data measured with at least one pair of receiving electrodes and / or the 3-axis magnetometer mount.

10. System, according to claim 9, characterized by the fact that the processor is configured to increase the sensitivity of the measured data when using the Synthetic Aperture method.

11. A method for detecting and delineating an object that is at least partially buried in the seabed, the method comprising the steps of: providing a system for detecting and delineating an object defined in any of claims 1 to 10, transmitting electromagnetic energy from a controlled electric dipole source (3) mounted on the hull of an Autonomous Underwater Vehicle (1) or on a cable (10) towed behind an Unmanned Surface Vehicle (8), the method characterized in that it further comprises the steps of: measuring a magnetic field with at least one 3-axis magnetometer mount (7) mounted on the hull of the AUV (1) or within a cable (10) towed behind the USV (8), and processing measured data with a processor located onboard the AUV (1) or USV (8).

12. Method according to claim 11, characterized in that it further comprises the steps: arranging a first pair of receiving electrodes (4) comprising vertical receiving electrodes (4a, 4b) mounted on the AUV hull (1) or within a cable (10) towed behind the USV (8), the vertical receiving electrodes (4a, 4b) are separated from each other in the vertical direction of the AUV (1), and measuring electric field with the receiving electrodes (4).

13. Method according to claim 11 or 12, characterized in that it further comprises the steps of: Petition 870260001039, dated 06 / 01 / 2026, p. 13 / 22 4 / 5 arranging a second receiver pair (5) comprising in-line receiver electrodes (5a, 5b) mounted on the AUV hull (1), the receiver electrodes (5a, 5b) being separated from each other in the longitudinal direction of the AUV (1) or USV (8), arranging a third receiver pair (6) comprising cross-line receiver electrodes (6a, 6b) mounted on the AUV hull (1), the receiver electrodes (6a, 6b) being separated from each other in the cross-line direction of the AUV (1), and measuring the electric field with the receiver pair electrodes (4a, 4b, 5a, 5b, 6a, 6b) mounted on the AUV hull (1).

14. A method, according to any one of claims 11 to 13, characterized in that the electromagnetic energy transmitted by the controlled electric dipole source contains discrete frequencies between 1 and 1000 Hz.

15. A method, according to any one of claims 11 to 14, characterized in that the processor, when using the Synthetic Aperture method, normalizes the measured data with a background field and combines them with optimized weights.

16. Method, according to any one of claims 11 to 15, characterized in that the Synthetic Opening method is given as: A(w) = < dAL)Γ 4''42'.....d®. where En = r,W(L) E1 [Wi,W2, ^,W;]T AA = I7N(1)\ . '.) ... EjN(L) Enw, dB = ENbw , ENb = / £Wâ(1) ... £Wi) ^U(í.) ... EJVâ(L) the matrices EN and ENb containing magnetic or electric field values ​​for controlled electric dipole source positions 1,... J and all positions of Petition 870260001039, dated 06 / 01 / 2026, p. 14 / 22 5 / 5 receiver 1, ... , L, and w1... Wj denotes the weights.

17. Method, according to claim 16, characterized in that it optimizes the weights by minimizing the following function: P(w) = \\D — A(w)||2 + a||dw||2 where the vector D is a projected Synthetic Opening, a is a regularization parameter, and dw are consecutive changes of the weights Wj.

18. Method, according to claim 16 or 17, characterized in that it further comprises: obtaining the conductivity structure of the buried object by feeding the processed data into a trained Convolutional Neural Network. Petition 870260001039, dated 06 / 01 / 2026, pp. 15 / 22

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