A square array electromagnetic detection and routing positioning method for submarine cables

Abstract

The present invention discloses a square array electromagnetic detection and routing positioning method for submarine cables. The method comprises: detecting the position information of a mother ship through a surface positioning system; detecting the electromagnetic signal of the submarine cable through a submarine cable detection system, detecting the vertical distance of the submarine cable detection and positioning platform relative to the seabed plane, the vertical distance relative to the sea level, and the bow deflection angle; detecting the position information of the submarine cable detection and positioning platform relative to the mother ship through an ultra-short baseline positioning system; using a submarine cable relative detection and positioning method to obtain the relative position information of the submarine cable and the square magnetic detector array; using a submarine cable absolute detection and positioning method to obtain the position information of the submarine cable, and realizing routing positioning of the submarine cable. In submarine cable detection operations, the method of the present invention can effectively improve the problems of the difficulty in accurately determining the relationship between the induction coil parameters and the induced electromotive force, inaccurate routing positioning, and improve the detection accuracy on the basis of reducing the complexity of the device.

Description

Technical Field

[0001] The present invention relates to a square array electromagnetic detection and routing positioning method, and in particular to a square array electromagnetic detection and routing positioning method for submarine cables. Background Art

[0002] Submarine cables are specially designed and manufactured to transmit AC or DC current across the ocean. The type of current and voltage transmitted depends on the capacity and length of the ocean transmission line. They can deliver power to islands, offshore platforms, and submarine observatories. Information about submarine cable installation primarily includes spatial location and routing. Spatial location refers to the lateral and vertical position of the submarine cable, while routing refers to the path the cable takes on the seabed from its starting point to its destination, which is typically a strip.

[0003] The use of submarine cables has increased significantly in recent years and is expected to continue to grow in the future. Burying submarine cables beneath the seabed is the most effective way to protect them. However, after laying, submarine cables can experience varying degrees of displacement, exposure, and other forms of natural damage due to scouring, corrosion, and submarine geological disasters. Furthermore, with the increasing frequency of marine economic and development activities, incidents of human-caused damage are rapidly increasing. Submarine cable engineering is one of the most complex and challenging large-scale projects in the marine industry. Compared to terrestrial cables, submarine cable engineering is even more complex and challenging. Fault detection is often not immediately possible, and repair cycles are lengthy, resulting in unpredictable consequences. Therefore, routine inspection and maintenance of submarine cables are becoming increasingly important. Accurate and rapid access to submarine cable installation information is a prerequisite for other tasks. It provides valuable basic data for routine maintenance and overhaul, and can also be used in emergency rescue and repair operations to ensure the normal operation of submarine cables. However, current technical challenges include the difficulty in accurately determining the relationship between induction coil parameters and induced electromotive force during submarine cable detection operations, as well as inaccurate submarine cable routing. Summary of the Invention

[0004] To address the problems in the background art, the present invention provides a square array electromagnetic detection and routing location method for submarine cables. Addressing the needs of submarine cable detection and routing location, the present invention employs an active detection method, also known as an AC magnetic field detection method. The basic principle of the active detection method is to apply an AC current of a certain frequency to the metallic layer of a submarine cable, causing the submarine cable to generate an electromagnetic field that propagates into the surrounding space. Specific detectors receive the electromagnetic wave signals around the submarine cable within an appropriate distance, process and analyze them, and thereby determine the submarine cable's position in a geodetic coordinate system. Applying the principles of active AC magnetic field detection, a submarine cable detection and positioning algorithm based on a square magnetic detector array is designed. The final output information primarily includes the submarine cable trajectory in a geodetic coordinate system, routing angles, routing point latitude and longitude information, and burial depth relative to the seabed and sea level. The present invention comprehensively considers the various relative positions of the square magnetic detector array and the submarine cable during underwater detection operations by an underwater detection platform, resulting in more accurate detection and positioning results. This provides a highly accurate submarine cable detection and routing location solution for routine submarine cable operations and maintenance.

[0005] The technical solution adopted in the present invention is:

[0006] The square array electromagnetic detection and routing positioning method of the present invention comprises the following steps:

[0007] Step 1: Sail the mother ship equipped with a surface positioning system and an ultra-short baseline positioning system to the sea surface above the submarine cable. The ultra-short baseline positioning system includes a first signal transceiver and a second signal transceiver. The first signal transceiver is installed on the bottom of the mother ship. Arrange the submarine cable detection system in the sea water above the submarine cable. The submarine cable detection system includes a submarine cable detection and positioning platform, a square magnetic detector array, a bottom altimeter, a depth sensor, an attitude sensor and a second signal transceiver.

[0008] Step 2: Detect the position information of the mother ship through the surface positioning system; detect the electromagnetic signal generated by the submarine cable through the square magnetic detector array, detect the vertical distance of the submarine cable detection positioning platform relative to the seabed plane through the bottom altimeter, detect the vertical distance of the submarine cable detection positioning platform relative to the sea level through the depth sensor, detect the bow angle of the submarine cable detection positioning platform through the attitude sensor, and detect the position information of the submarine cable detection positioning platform relative to the mother ship through the first signal transceiver and the second signal transceiver.

[0009] Step 3: Based on the electromagnetic signal generated by the submarine cable, the relative position information of the submarine cable and the square magnetic detector array is obtained using the submarine cable relative detection and positioning method.

[0010] Step 4: Based on the relative position information of the submarine cable and the square magnetic detector array, the position information of the mother ship, the vertical distance of the submarine cable detection and positioning platform relative to the seabed plane, the vertical distance of the submarine cable detection and positioning platform relative to the sea level, the heading angle of the submarine cable detection and positioning platform, and the position information of the submarine cable detection and positioning platform relative to the mother ship, the submarine cable position information is obtained using the submarine cable absolute detection and positioning method, and the route positioning of the submarine cable is finally achieved. The position information is all in the geodetic coordinate system.

[0011] In step 1, the submarine cable detection and positioning platform is arranged horizontally, the square magnetic detector array and the bottom altimeter are installed on the bottom surface of the submarine cable detection and positioning platform, the depth sensor and the attitude sensor are installed inside the submarine cable detection and positioning platform, and the second signal transceiver is installed on the top surface of the submarine cable detection and positioning platform; the square magnetic detector array includes a rigid square frame and four coil-type magnetic detectors, the rigid square frame is installed on the bottom surface of the submarine cable detection and positioning platform, and the four coil-type magnetic detectors are vertically and symmetrically arranged on the four bottom vertices of the rigid square frame; the four coil-type magnetic detectors are detector No. 1, detector No. 2, detector No. 3 and detector No. 4 respectively. During installation, ensure that the line connecting detectors No. 1 and No. 3 is parallel to the bow centerline of the underwater detection platform, the line connecting detectors No. 2 and No. 4 is parallel to the lateral centerline of the underwater detection platform, and the center of the square magnetic detector array is as close as possible to the bottom center of the underwater detection platform. When performing detection operations, the underwater detection platform should try to remain parallel to the seabed plane.

[0012] In step three, based on the electromagnetic signal generated by the submarine cable, a submarine cable relative detection and positioning method is used to obtain the relative position information of the submarine cable and the square magnetic detector array. That is, a lateral distance detection algorithm is used to obtain the lateral distance γ0 of the submarine cable relative to the square magnetic detector array, a vertical distance detection algorithm is used to obtain the vertical distance H of the submarine cable relative to the square magnetic detector array, and a heading angle detection algorithm is used to obtain the heading angle ψ of the submarine cable relative to the square magnetic detector array, as follows:

[0013]

[0014] Where A, B, and C are the first, second, and third coefficient matrices, respectively, of the submarine cable relative detection and positioning method; γ0 is the lateral distance matrix, γ0 = [γ γ] T , γ is the lateral distance from the center point of the square magnetic detector array to the vertical plane where the submarine cable is located; ψ is the heading angle matrix, ψ=[sin|ψ|cos|ψ|] T , |ψ|∈[0°,90°); η is the coordinate matrix, η=[xy] T; A relative coordinate system is established with the center point of the square magnetic detector array as the origin O, the line connecting the center point of the square magnetic detector array and detector No. 1 as the positive half axis of the x-axis, the line connecting the center point of the square magnetic detector array and detector No. 2 as the positive half axis of the y-axis, and the perpendicular line between the center point of the square magnetic detector array and the seabed plane as the positive half axis of the z-axis, wherein x and y are respectively the x-axis coordinate and y-axis coordinate of the intersection point obtained by drawing a perpendicular line from the center point of the square magnetic detector array to the seabed cable in the relative coordinate system; z is the z-axis coordinate of the intersection point obtained by drawing a perpendicular line from the center point of the square magnetic detector array to the seabed cable in the relative coordinate system; since in practice the seabed cable detection and positioning platform generally carries out detection operations in the positive direction from one end to the other end of the seabed cable, |ψ|∈[0°, 90°), combined with the relative position relationship between the square magnetic detector array and the seabed cable, when the movement direction of the square magnetic detector array is tilted to the right relative to the direction of the seabed cable, ψ=|ψ| is defined, and when the movement direction of the square magnetic detector array is tilted to the left relative to the direction of the seabed cable, ψ=-|ψ| is defined; the positive direction of the x-axis is the forward direction of the detection platform.

[0015] The lateral distance γ of the submarine cable relative to the square magnetic detector array is as follows:

[0016] γ=[γ1 γ2 γ3 γ4] T

[0017] Among them, γ1, γ2, γ3 and γ4 are the lateral distances from detectors 1, 2, 3 and 4 to the vertical plane where the submarine cable is located.

[0018] The first coefficient matrix A, the second coefficient matrix B, and the third coefficient matrix C of the submarine cable relative detection and positioning method are determined according to the induced electromotive force output by detectors 1, 2, 3, and 4 and the maximum value of their absolute values, as follows:

[0019] In actual submarine cable detection operations, there may be situations where all four detectors are located on one side of the submarine cable, one detector is located on one side of the submarine cable and the other three detectors are located on the other side of the submarine cable, or two detectors are located on one side of the submarine cable and the other two detectors are located on one of the other sides of the submarine cable. For a more specific analysis, by discussing V1, V2, V3, V4 and |V1| max 、|V2| max 、|V3| max 、|V4| max The relative position relationship between the submarine cable and the square magnetic detector array can be summarized and divided into 16 situations.

[0020] a) If V1·V3>0, V2·V4>0, |V1| max >|V3| max ,|V2| max >|V4| max, then the submarine cable and the square magnetic detector array are in the first relative position relationship, at this time:

[0021]

[0022] Among them, V1, V2, V3, and V4 are the induced electromotive forces output by detectors 1, 2, 3, and 4 respectively; |V1| max 、|V2| max 、|V3| max 、|V4| max are the maximum absolute values ​​of the induced electromotive force output by detectors 1, 2, 3, and 4 respectively;

[0023] b) If V1·V3>0, V2·V4>0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the second relative position relationship, at this time:

[0024]

[0025] c) If V1·V3>0, V2·V4>0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the third relative position relationship, at this time:

[0026]

[0027] d) If V1·V3>0, V2·V4>0, |V1| max >|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the fourth relative position relationship, at this time:

[0028]

[0029] e) If V1·V3<0, V2·V4>0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the fifth relative position relationship, at this time:

[0030]

[0031] f) If V1·V3<0, V2·V4>0, |V1| max >|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the sixth relative position relationship, at this time:

[0032]

[0033] g) If V1·V3>0, V2·V4<0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the seventh relative position relationship, at this time:

[0034]

[0035] h) If V1·V3>0, V2·V4<0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the eighth relative position relationship, at this time:

[0036]

[0037] i) If V1·V3<0, V2·V4>0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the ninth relative position relationship, at this time:

[0038]

[0039] j) If V1·V3<0, V2·V4>0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the tenth relative position relationship, at this time:

[0040]

[0041] k) If V1·V3>0, V2·V4<0, |V1| max >|V3| max ,|V2| max <|V4|max , then the submarine cable and the square magnetic detector array are in the eleventh relative position relationship, at this time:

[0042]

[0043] l) If V1·V3>0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the twelfth relative position relationship, at this time:

[0044]

[0045] m) If V1·V3<0, V2·V4<0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the thirteenth relative position relationship, at this time:

[0046]

[0047] n) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the fourteenth relative position relationship, at this time:

[0048]

[0049] o) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the fifteenth relative position relationship, at this time:

[0050]

[0051] p) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the sixteenth relative position relationship, at this time:

[0052]

[0053] When a single vertically positioned detector is located on different sides of a submarine cable, the magnetic flux lines pass through the induction coil in opposite directions. According to Faraday's law of electromagnetic induction, the signs of the induced electromotive force (EMF) of the detectors on either side of the submarine cable will also be opposite. When the vertical distance of the square magnetic detector array from the seabed plane is constant, the greater the absolute value of the lateral distance between the detector and the vertical plane of the submarine cable, the weaker the induced electromotive force (EMF) and the smaller its absolute value. In practice, underwater detection platforms generally conduct detection operations in a forward direction from one end of the submarine cable to the other. Therefore, it can be assumed that the absolute value of the angle between the movement direction of the square magnetic detector array and the submarine cable routing direction will not exceed 90°. Taking these factors into account, the relative position relationship between the square magnetic detector array and the submarine cable is divided into 16 cases.

[0054] The maximum absolute value of the induced electromotive force output by detectors 1, 2, 3, and 4 |V1| max 、|V2| max 、|V3| max 、|V4| max The details are as follows:

[0055]

[0056] Among them, |V i | max is the maximum absolute value of the induced electromotive force output by detector i, i = 1, 2, 3, 4; λ is the preset initial coefficient of the induced electromotive force; γ i is the lateral distance from detector i to the vertical plane where the submarine cable is located; is the electromagnetic attenuation coefficient at detector i; f is the frequency of the alternating current; μ is the magnetic permeability of seawater; σ is the electrical conductivity of seawater.

[0057] Active AC submarine cables will stimulate the generation of alternating electromagnetic fields. Combined with the relative position relationship between the square magnetic detector array and the magnetic flux lines in space and the attenuation law of the electromagnetic field in seawater, the maximum absolute value of the induced electromotive force output by the detector can be obtained. Its value is related to the number of turns of the detector coil, the effective area of ​​the coil (the area component perpendicular to the direction of the magnetic flux lines), the vacuum magnetic permeability, the maximum AC current and some other factors. Since the four detectors are produced with the same specifications, it is assumed that the initial coefficients of the induced electromotive force of the four detectors are the same in real time.

[0058] In the step three, based on the relative position information of the submarine cable and the square magnetic detector array, the position information of the mother ship, the vertical distance of the submarine cable detection and positioning platform relative to the seabed plane, the vertical distance of the submarine cable detection and positioning platform relative to the sea level, the bow deflection angle of the submarine cable detection and positioning platform, and the position information of the submarine cable detection and positioning platform relative to the mother ship, the position information of the submarine cable is obtained using the submarine cable absolute detection and positioning method, that is, the burial depth of the submarine cable relative to the seabed plane and the burial depth relative to the sea level are obtained respectively using the burial depth positioning algorithm, the routing direction positioning algorithm is used to obtain the various routing angles of the submarine cable, the routing point positioning algorithm is used to obtain the longitude and latitude information of each routing point of the submarine cable, and the routing point interpolation fitting method is used to obtain the submarine cable trajectory.

[0059] The method of using the buried depth positioning algorithm to obtain the buried depth of the submarine cable relative to the seabed plane and the buried depth relative to the sea level is as follows:

[0060] a) The buried depth h of the submarine cable relative to the seabed plane:

[0061] h=Hs

[0062] Where H is the vertical distance between the submarine cable and the square magnetic detector array; s is the vertical distance between the submarine cable detection and positioning platform and the seabed plane. Since the bottom altimeter and the square magnetic detector array are both installed at the bottom of the detection and positioning platform, and the detection and positioning platform is horizontal during operation, s can also be considered as the vertical distance between the square magnetic detector array and the seabed plane.

[0063] b) The burial depth D of the submarine cable relative to the sea level:

[0064] d=d d +Δd

[0065] D=d d +H

[0066] Where d is the vertical distance of the submarine cable detection and positioning platform relative to the sea level. Since the depth sensor is generally installed in the cabin of the detection and positioning platform, the vertical distance from the square magnetic detector array to the sea level should be the sum of the vertical distance from the depth sensor to the sea level and the vertical distance from the depth meter to the square magnetic detector array; d d is the vertical distance from the depth sensor to the sea level; Δd is the vertical distance from the depth sensor to the square magnetic detector array.

[0067] The routing direction positioning algorithm is used to obtain the various routing angles of the submarine cable. For each routing point of the submarine cable, the details are as follows:

[0068] ψ c =ψ+ψd

[0069] Among them, ψ c is the routing angle of the submarine cable routing point in the geodetic coordinate system; ψ is the heading angle of the submarine cable relative to the square magnetic detector array; ψ d is the heading angle of the submarine cable detection and positioning platform, ψ d ∈(-180°,180°], counterclockwise deflection is positive, clockwise deflection is negative. Since the square magnetic detector array has been installed to ensure that the connection line of detectors 1 and 3 is parallel to the bow centerline of the detection and positioning platform, ψ d It is also the heading deflection angle of the square array in the geodetic coordinate system.

[0070] The routing point positioning algorithm is used to obtain the longitude and latitude information of each routing point of the submarine cable. For each routing point of the submarine cable, the specific method is as follows:

[0071] E=E d +γcosψ c

[0072] N=N d -γsinψ c

[0073] Wherein, E is the latitude of the routing point of the submarine cable in the geodetic coordinate system, N is the longitude of the routing point of the submarine cable in the geodetic coordinate system, and the longitude and latitude information of the routing point is the routing point coordinates (E, N); E d The latitude of the submarine cable detection and positioning platform in the geodetic coordinate system outputted jointly by the first signal transceiver and the second signal transceiver of the ultra-short baseline positioning system and the surface positioning system; N d is the longitude of the submarine cable detection and positioning platform in the geodetic coordinate system jointly output by the ultra-short baseline positioning system and the surface positioning system. Since the absolute position difference between the square magnetic detector array and the submarine cable detection and positioning platform in the geodetic coordinate system is mainly concentrated in the vertical direction, (E d ,N d ) can also be considered as the latitude and longitude information of the square magnetic detector array in the geodetic coordinate system; γ is the lateral distance from the center point of the square magnetic detector array to the vertical plane where the submarine cable is located; ψ c It is the routing angle of the routing point of the submarine cable in the geodetic coordinate system.

[0074] The method of using routing point interpolation fitting to obtain the submarine cable trajectory is specifically to use the latitude and longitude information of each routing point of the submarine cable to perform interpolation fitting processing using the routing point interpolation fitting method to obtain the submarine cable trajectory in the geodetic coordinate system. The beneficial effects of the present invention are:

[0075] 1. The square magnetic detector array of the present invention reduces the complexity of the manufacturing process, is applicable to mass production applications, and improves engineering practicability.

[0076] 2 The algorithm adopted by the present invention introduces an initial coefficient of induced electromotive force, which can effectively avoid the influence of the common errors of the four detectors (such as the slight roll and tilt of the underwater detection platform causing the effective magnetic flux area of ​​the four detectors to change synchronously, the production and manufacturing errors of the detectors, the errors caused by the seabed mud and rocks on the propagation of electromagnetic waves, etc.) on the detection results, thereby improving the robustness of this scheme.

[0077] 3. The present invention analyzes 16 relative position relationships between the square magnetic detector array and the submarine cable, and provides corresponding solution algorithms for each case, thereby improving the adaptability of the solution.

[0078] 4. The underwater detection platform used in the present invention can be underwater equipment such as ROV, AUV or UUV. It only needs to ensure that the underwater detection platform maintains a relatively stable movement posture during operation and the current parameters of the submarine cable are known. There are no special requirements for parameters such as the cable width and model of the submarine cable, which improves the versatility of this solution.

[0079] 5. The present invention introduces a bottom altimeter, a depth gauge, an ultra-short baseline positioning system and a surface positioning system, which can accurately realize submarine cable detection and routing positioning operations in the geodetic coordinate system.

[0080] 6. In submarine cable detection operations, the method of the present invention can effectively improve problems such as the difficulty in accurately determining the relationship between the induction coil parameters and the induced electromotive force, inaccurate routing positioning, and improve detection accuracy while reducing the complexity of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 Longitudinal profile for submarine cable detection and routing operations;

[0082] Figure 2 It is the submarine cable track, routing point coordinates and routing angle map;

[0083] Figure 3 This is a simplified diagram of the square magnetic detector array structure;

[0084] Figure 4 It is a top view of the square magnetic detector array;

[0085] Figure 5 The diagram shows the position relationship between the vertically arranged detector and the electromagnetic field of the submarine cable;

[0086] Figure 6 This is a block diagram of the relative detection and positioning method for submarine cables;

[0087] Figure 7 This is a block diagram of the absolute detection and positioning method for submarine cables;

[0088] Figure 8 A top view of a first relative position relationship between the square magnetic detector array and the submarine cable;

[0089] Figure 9 A top view of the second relative position relationship between the square magnetic detector array and the submarine cable;

[0090] Figure 10 A top view of the third relative position relationship between the square magnetic detector array and the submarine cable;

[0091] Figure 11 A top view of the fourth relative position relationship between the square magnetic detector array and the submarine cable;

[0092] Figure 12 is a top view of the fifth relative position relationship between the square magnetic detector array and the submarine cable;

[0093] Figure 13 is a top view of the sixth relative position relationship between the square magnetic detector array and the submarine cable;

[0094] Figure 14 is a top view of the seventh relative position relationship between the square magnetic detector array and the submarine cable;

[0095] Figure 15 is a top view of the eighth relative position relationship between the square magnetic detector array and the submarine cable;

[0096] Figure 16 is a top view of the ninth relative position relationship between the square magnetic detector array and the submarine cable;

[0097] Figure 17 is a top view of the tenth relative position relationship between the square magnetic detector array and the submarine cable;

[0098] Figure 18 is a top view of the eleventh relative position relationship between the square magnetic detector array and the submarine cable;

[0099] Figure 19 A top view of the twelfth relative position relationship between the square magnetic detector array and the submarine cable;

[0100] Figure 20 A top view of the thirteenth relative position relationship between the square magnetic detector array and the submarine cable;

[0101] Figure 21 is a top view of the fourteenth relative position relationship between the square magnetic detector array and the submarine cable;

[0102] Figure 22 A top view of the fifteenth relative position relationship between the square magnetic detector array and the submarine cable;

[0103] Figure 23 This is a top view of the sixteenth relative position relationship between the square magnetic detector array and the submarine cable. DETAILED DESCRIPTION

[0104] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0105] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail with reference to the accompanying drawings. This description introduces specific embodiments consistent with the principles of the present invention by way of example and not limitation. The descriptions of these embodiments are detailed enough to enable those skilled in the art to practice the present invention. Other embodiments may be used and the structures of the various elements may be changed or replaced without departing from the scope and spirit of the present invention. Therefore, the following detailed description should not be understood in a restrictive sense.

[0106] The square array electromagnetic detection and routing positioning method of the present invention comprises the following steps:

[0107] Step 1: Sail the mother ship equipped with a surface positioning system and an ultra-short baseline positioning system to the sea surface above the submarine cable. The ultra-short baseline positioning system includes a first signal transceiver and a second signal transceiver. The first signal transceiver is installed on the bottom of the mother ship. Arrange the submarine cable detection system in the sea water above the submarine cable. The submarine cable detection system includes a submarine cable detection and positioning platform, a square magnetic detector array, a bottom altimeter, a depth sensor, an attitude sensor and a second signal transceiver.

[0108] In step one, the submarine cable detection and positioning platform is arranged horizontally, the square magnetic detector array and the bottom altimeter are installed on the bottom surface of the submarine cable detection and positioning platform, the depth sensor and the attitude sensor are installed inside the submarine cable detection and positioning platform, and the second signal transceiver is installed on the top surface of the submarine cable detection and positioning platform; the square magnetic detector array includes a rigid square frame and four coil-type magnetic detectors. The rigid square frame is installed on the bottom surface of the submarine cable detection and positioning platform, and the four coil-type magnetic detectors are vertically and symmetrically arranged on the four bottom vertices of the rigid square frame; the four coil-type magnetic detectors are detector No. 1, detector No. 2, detector No. 3 and detector No. 4 respectively. During installation, ensure that the line connecting detectors No. 1 and No. 3 is parallel to the bow centerline of the underwater detection platform, the line connecting detectors No. 2 and No. 4 is parallel to the lateral centerline of the underwater detection platform, and the center of the square magnetic detector array is as close as possible to the bottom center of the underwater detection platform. When performing detection operations, the underwater detection platform should try to remain parallel to the seabed plane.

[0109] Step 2: Detect the position information of the mother ship through the surface positioning system; detect the electromagnetic signal generated by the submarine cable through the square magnetic detector array, detect the vertical distance of the submarine cable detection positioning platform relative to the seabed plane through the bottom altimeter, detect the vertical distance of the submarine cable detection positioning platform relative to the sea level through the depth sensor, detect the bow angle of the submarine cable detection positioning platform through the attitude sensor, and detect the position information of the submarine cable detection positioning platform relative to the mother ship through the first signal transceiver and the second signal transceiver.

[0110] Step 3: Based on the electromagnetic signal generated by the submarine cable, the relative position information of the submarine cable and the square magnetic detector array is obtained using the submarine cable relative detection and positioning method.

[0111] In step three, based on the electromagnetic signal generated by the submarine cable, the relative position information of the submarine cable and the square magnetic detector array is obtained using the submarine cable relative detection and positioning method. That is, the lateral distance γ0 of the submarine cable relative to the square magnetic detector array is obtained using the lateral distance detection algorithm, the vertical distance H of the submarine cable relative to the square magnetic detector array is obtained using the vertical distance detection algorithm, and the heading angle ψ of the submarine cable relative to the square magnetic detector array is obtained using the heading angle detection algorithm. The details are as follows:

[0112]

[0113] Where A, B, and C are the first, second, and third coefficient matrices, respectively, of the submarine cable relative detection and positioning method; γ0 is the lateral distance matrix, γ0 = [γ γ] T , γ is the lateral distance from the center point of the square magnetic detector array to the vertical plane where the submarine cable is located; ψ is the heading angle matrix, ψ=[sin|ψ|cos|ψ|] T , |ψ|∈[0°,90°); η is the coordinate matrix, η=[xy] T; A relative coordinate system is established with the center point of the square magnetic detector array as the origin O, the line connecting the center point of the square magnetic detector array and detector No. 1 as the positive half axis of the x-axis, the line connecting the center point of the square magnetic detector array and detector No. 2 as the positive half axis of the y-axis, and the perpendicular line between the center point of the square magnetic detector array and the seabed plane as the positive half axis of the z-axis, wherein x and y are respectively the x-axis coordinate and y-axis coordinate of the intersection point obtained by drawing a perpendicular line from the center point of the square magnetic detector array to the seabed cable in the relative coordinate system; z is the z-axis coordinate of the intersection point obtained by drawing a perpendicular line from the center point of the square magnetic detector array to the seabed cable in the relative coordinate system; since in practice the seabed cable detection and positioning platform generally carries out detection operations in the positive direction from one end to the other end of the seabed cable, |ψ|∈[0°, 90°), combined with the relative position relationship between the square magnetic detector array and the seabed cable, when the movement direction of the square magnetic detector array is tilted to the right relative to the direction of the seabed cable, ψ=|ψ| is defined, and when the movement direction of the square magnetic detector array is tilted to the left relative to the direction of the seabed cable, ψ=-|ψ| is defined; the positive direction of the x-axis is the forward direction of the detection platform.

[0114] The lateral distance γ of the submarine cable relative to the square magnetic detector array is as follows:

[0115] γ=[γ1 γ2 γ3 γ4] T

[0116] Among them, γ1, γ2, γ3 and γ4 are the lateral distances from detectors 1, 2, 3 and 4 to the vertical plane where the submarine cable is located.

[0117] The first coefficient matrix A, the second coefficient matrix B, and the third coefficient matrix C of the relative detection and positioning method for submarine cables are determined according to the maximum value of the induced electromotive force output by detectors 1, 2, 3, and 4 and their absolute values, as follows:

[0118] In actual submarine cable detection operations, there may be situations where all four detectors are located on one side of the submarine cable, one detector is located on one side of the submarine cable and the other three detectors are located on the other side of the submarine cable, or two detectors are located on one side of the submarine cable and the other two detectors are located on one of the other sides of the submarine cable. For a more specific analysis, by discussing V1, V2, V3, V4 and |V1| max 、|V2| max 、|V3| max 、|V4| max The relative position relationship between the submarine cable and the square magnetic detector array can be summarized and divided into 16 situations.

[0119] a) If V1·V3>0, V2·V4>0, |V1| max >|V3| max ,|V2| max >|V4| max, then the submarine cable and the square magnetic detector array are in the first relative position relationship, at this time:

[0120]

[0121] Among them, V1, V2, V3, and V4 are the induced electromotive forces output by detectors 1, 2, 3, and 4 respectively; |V1| max 、|V2| max 、|V3| max 、|V4| max These are the maximum absolute values ​​of the induced electromotive force output by detectors 1, 2, 3, and 4 respectively.

[0122] b) If V1·V3>0, V2·V4>0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the second relative position relationship, at this time:

[0123]

[0124] c) If V1·V3>0, V2·V4>0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the third relative position relationship, at this time:

[0125]

[0126] d) If V1·V3>0, V2·V4>0, |V1| max >|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the fourth relative position relationship, at this time:

[0127]

[0128] e) If V1·V3<0, V2·V4>0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the fifth relative position relationship, at this time:

[0129]

[0130] f) If V1·V3<0, V2·V4>0, |V1| max >|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the sixth relative position relationship, at this time:

[0131]

[0132] g) If V1·V3>0, V2·V4<0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the seventh relative position relationship, at this time:

[0133]

[0134] h) If V1·V3>0, V2·V4<0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the eighth relative position relationship, at this time:

[0135]

[0136] i) If V1·V3<0, V2·V4>0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the ninth relative position relationship, at this time:

[0137]

[0138] j) If V1·V3<0, V2·V4>0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the tenth relative position relationship, at this time:

[0139]

[0140] k) If V1·V3>0, V2·V4<0, |V1| max >|V3| max ,|V2| max <|V4|max , then the submarine cable and the square magnetic detector array are in the eleventh relative position relationship, at this time:

[0141]

[0142] l) If V1·V3>0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the twelfth relative position relationship, at this time:

[0143]

[0144] m) If V1·V3<0, V2·V4<0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the thirteenth relative position relationship, at this time:

[0145]

[0146] n) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the fourteenth relative position relationship, at this time:

[0147]

[0148] o) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the fifteenth relative position relationship, at this time:

[0149]

[0150] p) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the sixteenth relative position relationship, at this time:

[0151]

[0152] When a single vertically positioned detector is located on different sides of a submarine cable, the magnetic flux lines pass through the induction coil in opposite directions. According to Faraday's law of electromagnetic induction, the signs of the induced electromotive force (EMF) of the detectors on either side of the submarine cable will also be opposite. When the vertical distance of the square magnetic detector array from the seabed plane is constant, the greater the absolute value of the lateral distance between the detector and the vertical plane of the submarine cable, the weaker the induced electromotive force (EMF) and the smaller its absolute value. In practice, underwater detection platforms generally conduct detection operations in a forward direction from one end of the submarine cable to the other. Therefore, it can be assumed that the absolute value of the angle between the movement direction of the square magnetic detector array and the submarine cable routing direction will not exceed 90°. Taking these factors into account, the relative position relationship between the square magnetic detector array and the submarine cable is divided into 16 cases.

[0153] The maximum absolute value of the induced electromotive force output by detectors 1, 2, 3, and 4 |V1| max 、|V2| max 、|V3| max 、|V4| max The details are as follows:

[0154]

[0155] Among them, |V i | max is the maximum absolute value of the induced electromotive force output by detector i, i = 1, 2, 3, 4; λ is the preset initial coefficient of the induced electromotive force; γ i is the lateral distance from detector i to the vertical plane where the submarine cable is located; is the electromagnetic attenuation coefficient at detector i; f is the frequency of the alternating current; μ is the magnetic permeability of seawater; σ is the electrical conductivity of seawater.

[0156] Active AC submarine cables will stimulate the generation of alternating electromagnetic fields. Combined with the relative position relationship between the square magnetic detector array and the magnetic flux lines in space and the attenuation law of the electromagnetic field in seawater, the maximum absolute value of the induced electromotive force output by the detector can be obtained. Its value is related to the number of turns of the detector coil, the effective area of ​​the coil (the area component perpendicular to the direction of the magnetic flux lines), the vacuum magnetic permeability, the maximum AC current and some other factors. Since the four detectors are produced with the same specifications, it is assumed that the initial coefficients of the induced electromotive force of the four detectors are the same in real time.

[0157] In step three, based on the relative position information of the submarine cable and the square magnetic detector array, the position information of the mother ship, the vertical distance of the submarine cable detection and positioning platform relative to the seabed plane, the vertical distance of the submarine cable detection and positioning platform relative to the sea level, the bow deflection angle of the submarine cable detection and positioning platform, and the position information of the submarine cable detection and positioning platform relative to the mother ship, the position information of the submarine cable is obtained using the submarine cable absolute detection and positioning method, that is, the burial depth of the submarine cable relative to the seabed plane and the burial depth relative to the sea level are obtained using the burial depth positioning algorithm, the routing direction positioning algorithm is used to obtain the various routing angles of the submarine cable, the routing point positioning algorithm is used to obtain the longitude and latitude information of each routing point of the submarine cable, and the routing point interpolation fitting method is used to obtain the submarine cable trajectory.

[0158] Use the burial depth positioning algorithm to obtain the buried depth of the submarine cable relative to the seabed plane and the buried depth relative to the sea level, as follows:

[0159] a) The buried depth h of the submarine cable relative to the seabed plane:

[0160] h=Hs

[0161] Where H is the vertical distance between the submarine cable and the square magnetic detector array; s is the vertical distance between the submarine cable detection and positioning platform and the seabed plane. Since the bottom altimeter and the square magnetic detector array are both installed at the bottom of the detection and positioning platform, and the detection and positioning platform is horizontal during operation, s can also be considered as the vertical distance between the square magnetic detector array and the seabed plane.

[0162] b) The burial depth D of the submarine cable relative to the sea level:

[0163] d=d d +Δd

[0164] D=d d +H

[0165] Where d is the vertical distance of the submarine cable detection and positioning platform relative to the sea level. Since the depth sensor is generally installed in the cabin of the detection and positioning platform, the vertical distance from the square magnetic detector array to the sea level should be the sum of the vertical distance from the depth sensor to the sea level and the vertical distance from the depth meter to the square magnetic detector array; d d is the vertical distance from the depth sensor to the sea level; Δd is the vertical distance from the depth sensor to the square magnetic detector array.

[0166] Use the routing direction positioning algorithm to obtain the various routing angles of the submarine cable. For each routing point of the submarine cable, the details are as follows:

[0167] ψ c =ψ+ψ d

[0168] Among them, ψ c is the routing angle of the submarine cable routing point in the geodetic coordinate system; ψ is the heading angle of the submarine cable relative to the square magnetic detector array; ψ d is the heading angle of the submarine cable detection and positioning platform, ψ d ∈(-180°,180°], counterclockwise deflection is positive, clockwise deflection is negative. Since the square magnetic detector array has been installed to ensure that the connection line of detectors 1 and 3 is parallel to the bow centerline of the detection and positioning platform, ψ d It is also the heading deflection angle of the square array in the geodetic coordinate system.

[0169] Use the routing point positioning algorithm to obtain the latitude and longitude information of each routing point of the submarine cable. For each routing point of the submarine cable, the details are as follows:

[0170] E=E d +γcosψ c

[0171] N=N d -γsinψ c

[0172] Wherein, E is the latitude of the routing point of the submarine cable in the geodetic coordinate system, N is the longitude of the routing point of the submarine cable in the geodetic coordinate system, and the longitude and latitude information of the routing point is the routing point coordinates (E, N); E d The latitude of the submarine cable detection and positioning platform in the geodetic coordinate system outputted jointly by the first signal transceiver and the second signal transceiver of the ultra-short baseline positioning system and the surface positioning system; N d is the longitude of the submarine cable detection and positioning platform in the geodetic coordinate system jointly output by the ultra-short baseline positioning system and the surface positioning system. Since the absolute position difference between the square magnetic detector array and the submarine cable detection and positioning platform in the geodetic coordinate system is mainly concentrated in the vertical direction, (E d ,N d ) can also be considered as the latitude and longitude information of the square magnetic detector array in the geodetic coordinate system; γ is the lateral distance from the center point of the square magnetic detector array to the vertical plane where the submarine cable is located; ψ c It is the routing angle of the routing point of the submarine cable in the geodetic coordinate system.

[0173] The routing point interpolation fitting method is used to obtain the submarine cable trajectory. Specifically, the longitude and latitude information of each routing point of the submarine cable is obtained by interpolation fitting using the routing point interpolation fitting method to obtain the submarine cable trajectory in the geodetic coordinate system.

[0174] Step 4: Based on the relative position information of the submarine cable and the square magnetic detector array, the position information of the mother ship, the vertical distance of the submarine cable detection and positioning platform relative to the seabed plane, the vertical distance of the submarine cable detection and positioning platform relative to the sea level, the heading angle of the submarine cable detection and positioning platform, and the position information of the submarine cable detection and positioning platform relative to the mother ship, the submarine cable position information is obtained using the submarine cable absolute detection and positioning method, and the route positioning of the submarine cable is finally achieved. The position information is all in the geodetic coordinate system.

[0175] The present invention discloses a square array electromagnetic detection and routing positioning method for submarine cables, in order to obtain submarine cable tracks, routing angles, routing point longitude and latitude information, burial depth relative to the seabed plane, and burial depth relative to the sea level in a geodetic coordinate system, such as Figure 1 and Figure 2 shown.

[0176] The present invention mainly includes a square magnetic detector array, a bottom altimeter, a depth sensor, a posture sensor, an ultra-short baseline positioning system and a water surface positioning system. The square magnetic detector array is as follows: Figure 3 and Figure 4 As shown in the figure, a square magnetic detector array, used to collect magnetic signals, consists of four coil-type magnetic detectors and a rigid square frame. The four coil-type magnetic detectors are arranged vertically and symmetrically at the four vertices of the rigid square frame. The square magnetic detector array is installed horizontally on the bottom of the underwater detection platform. During installation, ensure that the line connecting detectors 1 and 3 is parallel to the platform's bow centerline, and the line connecting detectors 2 and 4 is parallel to the platform's transverse centerline. A bottom altimeter measures the vertical distance of the underwater detection platform relative to the seabed in real time. Since both the square magnetic detector array and the bottom altimeter are installed horizontally on the bottom of the underwater detection platform, this vertical distance can be considered the vertical distance of the square magnetic detector array relative to the seabed and is used to calculate the buried depth of the submarine cable relative to the seabed. A depth sensor measures the vertical distance of the underwater detection platform relative to the seabed in real time and is used to calculate the buried depth of the submarine cable relative to the seabed. The attitude sensor outputs the underwater detection platform's bow deflection in real time. Combined with the deflection of the submarine cable routing direction relative to the movement direction of the square magnetic detector array, the submarine cable routing direction in the geodetic coordinate system can be calculated. The ultra-short baseline positioning system measures the relative position of the underwater detection platform and the surface mother ship in real time. The surface positioning system measures the position of the surface mother ship in real time in the geodetic coordinate system. Combined with the ultra-short baseline positioning system, the position of the underwater detection platform in the geodetic coordinate system can be calculated, and then the position of the submarine cable in the geodetic coordinate system can be calculated.

[0177] like Figure 5As shown, the present invention takes into account that when a single vertically positioned detector is located on different sides of a submarine cable, the magnetic flux lines pass through the induction coil in opposite directions. According to Faraday's law of electromagnetic induction, the signs of the induced electromotive force of the detectors on either side of the submarine cable will also be opposite. When the vertical distance of the square magnetic detector array from the seabed plane is constant, the greater the absolute value of the lateral distance of the detector from the vertical plane of the submarine cable, the weaker the induced electromotive force and the smaller the absolute value of the induced electromotive force. In practice, underwater detection platforms generally conduct detection operations in a forward direction from one end of the submarine cable to the other. Therefore, it can be assumed that the absolute value of the angle between the movement direction of the square magnetic detector array and the submarine cable routing direction will not exceed 90°. Taking these factors into consideration, a more detailed analysis is conducted by discussing V1, V2, V3, V4, and |V1| max 、|V2| max 、|V3| max 、|V4| max The relative position relationship between the square magnetic detector array and the submarine cable is divided into 16 cases, such as Figure 8-Figure 23 shown.

[0178] like Figure 6 As shown in the figure, the execution process of the relative detection and positioning algorithm for submarine cables is as follows: a relative coordinate system is established with the center point of the square magnetic detector array as the origin O, the line connecting the center point of the square magnetic detector array and detector No. 1 as the positive semi-axis of the x-axis, the line connecting the center point of the square magnetic detector array and detector No. 2 as the positive semi-axis of the y-axis, and the perpendicular line between the center point of the square magnetic detector array and the seabed plane as the positive semi-axis of the z-axis. The four real-time magnetic signals V provided by the square magnetic detector array are analyzed. i (i=1, 2, 3, 4), determine the relative position relationship between the square magnetic detector array and the submarine cable, and obtain the corresponding coefficient matrices A, B, and C. Then, the lateral distance γ, vertical distance H, and heading angle ψ of the submarine cable relative to the square magnetic detector array can be obtained.

[0179] like Figure 7 As shown in the figure, the execution process of the absolute detection and positioning algorithm of the submarine cable is as follows: according to the output of the relative detection and positioning algorithm of the submarine cable, combined with the real-time bottom height information of the underwater detection platform relative to the seabed provided by the bottom altimeter, the real-time depth information of the underwater detection platform relative to the sea level provided by the depth sensor, the position information of the underwater detection platform relative to the surface mother ship provided by the ultra-short baseline positioning system, and the position information of the surface mother ship in the geodetic coordinate system provided by the surface positioning system, the submarine cable trajectory and routing angle ψ in the geodetic coordinate system can be solved. c , longitude and latitude information (E, N), burial depth h relative to the seabed plane, and vertical distance D relative to the sea level.

[0180] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various similar changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention, which is defined by the appended claims and their equivalents.

Claims

1. A square array electromagnetic detection and routing positioning method for submarine cables, characterized by: The method comprises the following steps: Step 1: Navigate a mother ship equipped with a surface positioning system and an ultra-short baseline positioning system to the sea surface above the submarine cable. The ultra-short baseline positioning system includes a first signal transceiver and a second signal transceiver, and the first signal transceiver is installed on the bottom of the mother ship. Arrange a submarine cable detection system in the seawater above the submarine cable. The submarine cable detection system includes a submarine cable detection and positioning platform, a square magnetic detector array, a bottom altimeter, a depth sensor, an attitude sensor, and a second signal transceiver. Step 2: Detect the position information of the mother ship through the surface positioning system; detect the electromagnetic signal generated by the submarine cable through the square magnetic detector array, detect the vertical distance of the submarine cable detection positioning platform relative to the seabed plane through the bottom altimeter, detect the vertical distance of the submarine cable detection positioning platform relative to the sea level through the depth sensor, detect the heading angle of the submarine cable detection positioning platform through the attitude sensor, and detect the submarine cable detection positioning platform relative to the mother ship through the first signal transceiver and the second signal transceiver. Step 3: Based on the electromagnetic signal generated by the submarine cable, the relative position information of the submarine cable and the square magnetic detector array is obtained using the submarine cable relative detection and positioning method; Step 4: Based on the relative position information of the submarine cable and the square magnetic detector array, the position information of the mother ship, the vertical distance of the submarine cable detection and positioning platform relative to the seabed plane, the vertical distance of the submarine cable detection and positioning platform relative to the sea level, the bow angle of the submarine cable detection and positioning platform, and the position information of the submarine cable detection and positioning platform relative to the mother ship, the position information of the submarine cable is obtained using the submarine cable absolute detection and positioning method, and finally the route positioning of the submarine cable is realized.

2. A square array electromagnetic detection and routing positioning method for submarine cables according to claim 1, characterized in that: In the step 1, the submarine cable detection and positioning platform is arranged horizontally, the square magnetic detector array and the bottom altimeter are installed on the bottom surface of the submarine cable detection and positioning platform, the depth sensor and the attitude sensor are installed inside the submarine cable detection and positioning platform, and the second signal transceiver is installed on the top surface of the submarine cable detection and positioning platform; the square magnetic detector array includes a rigid square frame and four coil-type magnetic detectors, the rigid square frame is installed on the bottom surface of the submarine cable detection and positioning platform, and the four coil-type magnetic detectors are vertically and symmetrically arranged on the four bottom surface vertices of the rigid square frame; the four coil-type magnetic detectors are detector No. 1, detector No. 2, detector No. 3 and detector No. 4 respectively.

3. The square array electromagnetic detection and routing positioning method for submarine cables according to claim 2, characterized in that: In step three, based on the electromagnetic signal generated by the submarine cable, a submarine cable relative detection and positioning method is used to obtain the relative position information of the submarine cable and the square magnetic detector array. That is, a lateral distance detection algorithm is used to obtain the lateral distance γ0 of the submarine cable relative to the square magnetic detector array, a vertical distance detection algorithm is used to obtain the vertical distance H of the submarine cable relative to the square magnetic detector array, and a heading angle detection algorithm is used to obtain the heading angle ψ of the submarine cable relative to the square magnetic detector array, as follows: Where A, B, and C are the first, second, and third coefficient matrices of the relative detection and positioning method for submarine cables, respectively; γ0 is the lateral distance matrix, γ0 = [γγ] T , γ is the lateral distance from the center point of the square magnetic detector array to the vertical plane where the submarine cable is located; ψ is the heading angle matrix, ψ=[sin|ψ|cos|ψ|] T , |ψ|∈[0°,90°); η is the coordinate matrix, η=[xy] T ; A relative coordinate system is established with the center point of the square magnetic detector array as the origin O, the line connecting the center point of the square magnetic detector array and detector No. 1 as the positive half axis of the x-axis, the line connecting the center point of the square magnetic detector array and detector No. 2 as the positive half axis of the y-axis, and the perpendicular line between the center point of the square magnetic detector array and the seabed plane as the positive half axis of the z-axis. x and y are respectively the x-axis coordinate and y-axis coordinate of the intersection point obtained by drawing a perpendicular line from the center point of the square magnetic detector array to the submarine cable in the relative coordinate system; z is the z-axis coordinate of the intersection point obtained by drawing a perpendicular line from the center point of the square magnetic detector array to the submarine cable in the relative coordinate system; The lateral distance γ of the submarine cable relative to the square magnetic detector array is as follows: γ[γ1γ2γ3γ4] T Among them, γ1, γ2, γ3 and γ4 are the lateral distances from detectors 1, 2, 3 and 4 to the vertical plane where the submarine cable is located.

4. A square array electromagnetic detection and routing positioning method for submarine cables according to claim 3, characterized in that: The first coefficient matrix A, the second coefficient matrix B, and the third coefficient matrix C of the submarine cable relative detection and positioning method are determined according to the induced electromotive force output by detectors 1, 2, 3, and 4 and the maximum value of their absolute values, as follows: a) If V1·V3>0, V2·V4>0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the first relative position relationship, at this time: Among them, V1, V2, V3, and V4 are the induced electromotive forces output by detectors 1, 2, 3, and 4 respectively; |V1| max 、|V2| max 、|V3| max 、|V4| max are the maximum absolute values ​​of the induced electromotive force output by detectors 1, 2, 3, and 4 respectively; b) If V1·V3>0, V2·V4>0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the second relative position relationship, at this time: c) If V1·V3>0, V2·V4>0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the third relative position relationship, at this time: d) If V1·V3>0, V2·V4>0, |V1| max >|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the fourth relative position relationship, at this time: e) If V1·V3<0, V2·V4>0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the fifth relative position relationship, at this time: f) If V1·V3<0, V2·V4>0, |V1| max >|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the sixth relative position relationship, at this time: g) If V1·V3>0, V2·V4<0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the seventh relative position relationship, at this time: h) If V1·V3>0, V2·V4<0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the eighth relative position relationship, at this time: i) If V1·V3<0,V2·V4>0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the ninth relative position relationship, at this time: j) If V1·V3<0, V2·V4>0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the tenth relative position relationship, at this time: k) If V1·V3>0, V2·V4<0, |V1| max >|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the eleventh relative position relationship, at this time: l) If V1·V3>0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the twelfth relative position relationship, at this time: m) If V1·V3<0, V2·V4<0, |V1| max >|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the thirteenth relative position relationship, at this time: n) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max >|V4| max , then the submarine cable and the square magnetic detector array are in the fourteenth relative position relationship, at this time: o) If V1·V3<0, V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the fifteenth relative position relationship, at this time: p) If V1·V3<0,V2·V4<0, |V1| max <|V3| max ,|V2| max <|V4| max , then the submarine cable and the square magnetic detector array are in the sixteenth relative position relationship, at this time:

5. The square array electromagnetic detection and routing positioning method for submarine cables according to claim 4, characterized in that: The maximum absolute value of the induced electromotive force output by detectors 1, 2, 3, and 4 |V1| max 、|V2| max 、|V3| max 、|V4| max The details are as follows: Among them, |V i | max is the maximum absolute value of the induced electromotive force output by detector i, i = 1, 2, 3, 4; λ is the preset initial coefficient of the induced electromotive force; γ i is the lateral distance from detector i to the vertical plane where the submarine cable is located; is the electromagnetic attenuation coefficient at detector i; f is the frequency of the alternating current; μ is the magnetic permeability of seawater; σ is the electrical conductivity of seawater.

6. The square array electromagnetic detection and routing positioning method for submarine cables according to claim 2, characterized in that: In the step three, based on the relative position information of the submarine cable and the square magnetic detector array, the position information of the mother ship, the vertical distance of the submarine cable detection and positioning platform relative to the seabed plane, the vertical distance of the submarine cable detection and positioning platform relative to the sea level, the bow deflection angle of the submarine cable detection and positioning platform, and the position information of the submarine cable detection and positioning platform relative to the mother ship, the position information of the submarine cable is obtained using the submarine cable absolute detection and positioning method, that is, the burial depth of the submarine cable relative to the seabed plane and the burial depth relative to the sea level are obtained respectively using the burial depth positioning algorithm, the routing direction positioning algorithm is used to obtain the various routing angles of the submarine cable, the routing point positioning algorithm is used to obtain the longitude and latitude information of each routing point of the submarine cable, and the routing point interpolation fitting method is used to obtain the submarine cable trajectory.

7. A square array electromagnetic detection and routing positioning method for submarine cables according to claim 6, characterized in that: The method of using the buried depth positioning algorithm to obtain the buried depth of the submarine cable relative to the seabed plane and the buried depth relative to the sea level is as follows: a) The buried depth h of the submarine cable relative to the seabed plane: h=Hs Where H is the vertical distance between the submarine cable and the square magnetic detector array; s is the vertical distance between the submarine cable detection and positioning platform and the seabed plane; b) The burial depth D of the submarine cable relative to the sea level: d=d d +Δd D=d d +H Where d is the vertical distance of the submarine cable detection and positioning platform relative to the sea level; d is the vertical distance from the depth sensor to the sea level; Δd is the vertical distance from the depth sensor to the square magnetic detector array.

8. The square array electromagnetic detection and routing positioning method for submarine cables according to claim 6, characterized in that: The routing direction positioning algorithm is used to obtain the various routing angles of the submarine cable. For each routing point of the submarine cable, the details are as follows: ψ c =ψ+ψ d Among them, ψ c is the routing angle of the submarine cable routing point in the geodetic coordinate system; ψ is the heading angle of the submarine cable relative to the square magnetic detector array; ψ d is the heading angle of the submarine cable detection and positioning platform, ψ d ∈(-180°,180°], counterclockwise deflection is positive and clockwise deflection is negative.

9. The square array electromagnetic detection and routing positioning method for submarine cables according to claim 6, characterized in that: The routing point positioning algorithm is used to obtain the longitude and latitude information of each routing point of the submarine cable. For each routing point of the submarine cable, the specific method is as follows: E=E d +γcosψ c N=N d -γsinψ c Wherein, E is the latitude of the routing point of the submarine cable in the geodetic coordinate system, N is the longitude of the routing point of the submarine cable in the geodetic coordinate system, and the longitude and latitude information of the routing point is the routing point coordinates (E, N); E d The latitude of the submarine cable detection and positioning platform in the geodetic coordinate system outputted jointly by the first signal transceiver and the second signal transceiver of the ultra-short baseline positioning system and the surface positioning system; N d is the longitude of the submarine cable detection and positioning platform in the geodetic coordinate system jointly output by the ultra-short baseline positioning system and the surface positioning system; γ is the lateral distance from the center point of the square magnetic detector array to the vertical plane where the submarine cable is located; ψ c It is the routing angle of the routing point of the submarine cable in the geodetic coordinate system.

10. The square array electromagnetic detection and routing positioning method for submarine cables according to claim 6, characterized in that: The method of using the routing point interpolation fitting method to obtain the submarine cable trajectory is specifically to obtain the submarine cable trajectory in the geodetic coordinate system by performing interpolation fitting processing using the routing point interpolation fitting method through the longitude and latitude information of each routing point of the submarine cable.

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