An underwater magnetic anomaly target high-low air cooperative aviation magnetic detection method and system

Abstract

The application discloses a kind of high-low air cooperative aviation magnetic detection method and system of underwater magnetic anomaly target, it is related to weak magnetic target detection technical field.The technical points of the present application include: to the target to be measured of known detection distance, the magnetic signal detection is carried out using the cooperative flight of the dual unmanned aerial vehicle with magnetic anomaly detector, wherein the longitude and latitude of dual unmanned aerial vehicle is consistent at any time of flight, and the height is inconsistent;The magnetic signal detected by the unmanned aerial vehicle with lower flight height is upwardly extrapolated to the height corresponding to another unmanned aerial vehicle to update;The updated magnetic signal is data fused with the magnetic signal detected by the unmanned aerial vehicle with higher flight height;The magnetic anomaly detection signal after fusion, which does not contain the geomagnetic field, is judged using a magnetic target detection algorithm to determine whether the target to be measured is a weak magnetic target.The present application can quickly remove the cover of geomagnetic field on weak magnetic target signal, without post-processing the measured magnetic field, simple and fast, with real-time.

Description

Technical Field

[0001] This invention relates to the field of weak magnetic target detection technology, specifically to a high- and low-altitude coordinated airborne magnetic detection method and system for underwater magnetic anomaly targets. Background Technology

[0002] The Earth's magnetic field is a natural physical field with various origins, composed of magnetic field components with different variation patterns. The magnetic field generated by a magnetic target can cause changes in the distribution of the Earth's magnetic field in space, thus producing magnetic anomalies. When the distance between the observation point and the target is 2-3 times or more the size of the target, the magnetic field generated by the magnetic target is generally considered to be the far field of a magnetic dipole.

[0003] Using UAVs equipped with airborne magnetometers to detect underwater or underground magnetic targets is a common and effective method. When detecting weakly magnetic targets that generate weak magnetic anomalies underground or underwater, the geomagnetic field is usually considered a constant and stable magnetic field. However, the stable geomagnetic field also has certain magnetic properties. When detecting targets with inherently weak magnetic anomalies, the magnetic anomaly signal is often submerged in the geomagnetic field, making it difficult to detect. Especially before detecting weakly magnetic targets underwater or underground, filtering is often performed to remove the geomagnetic field. Since the distribution characteristics of the geomagnetic field are unknown, its frequency band in the airborne magnetic signal may overlap with the target signal's frequency band, thus affecting the weakly magnetic target signal in airborne magnetic anomaly detection.

[0004] In summary, existing technologies that utilize drones equipped with magnetic anomaly detection devices for underground or underwater magnetic anomaly detection are susceptible to the influence of the geomagnetic field. Therefore, how to remove the influence of the geomagnetic field during magnetic anomaly detection is a challenging problem that urgently needs to be solved. Summary of the Invention

[0005] In view of the above problems, this invention proposes a high-low altitude coordinated airborne magnetic detection method and system for underwater magnetic anomaly targets, so as to accurately, quickly and easily detect weakly magnetic targets underwater or underground.

[0006] According to one aspect of the present invention, a high- and low-altitude coordinated airborne magnetic detection method for underwater magnetic anomaly targets is proposed, the method comprising the following steps:

[0007] For a target with a known detection range, two unmanned aerial vehicles (UAVs) equipped with magnetic anomaly detectors are used to conduct magnetic signal detection through coordinated flight; the latitude and longitude of the two UAVs remain consistent at any time during flight, but their altitudes are inconsistent;

[0008] The magnetic signal detected by the drone with a lower flight altitude is upward continued to the altitude corresponding to another drone to obtain an updated magnetic signal;

[0009] The updated magnetic signal is fused with the magnetic signal detected by the drone with a higher flight altitude to obtain a magnetic anomaly detection signal that does not contain the geomagnetic field;

[0010] The magnetic target detection algorithm is used to judge the magnetic anomaly detection signal that does not contain the geomagnetic field to determine whether the待测目标 is a weak magnetic target.

[0011] In one possible implementation, the flight altitude of the dual drones is less than the known detection distance.

[0012] In one possible implementation, the magnetic signal is a magnetic signal that does not contain magnetic interference.

[0013] In one possible implementation, the upward continuation of the magnetic signal detected by the drone with a lower flight altitude to the altitude corresponding to another drone to obtain an updated magnetic signal includes:

[0014] The magnetic signal detected by the drone with a lower flight altitude is denoted as S 1 , the magnetic signal detected by the drone with a higher flight altitude is denoted as S 2 , S 1 , S 2 is the point corresponding to the aircraft trajectory, denoted as:

[0015]

[0016]

[0017] where N represents N points on the trajectory; As the output of the function f(x,y,z) representing the magnetic field at the observation point:

[0018]

[0019]

[0020] x i , y i are the coordinates of the observation point, H1 and H2 are the flight altitudes of the dual drones, and H1 < H2;

[0021] According to the output of the observation point magnetic field function f 1 corresponding to S 1 (x i , y i , H1), calculate its continuation to the plane z = H2 to obtain the updated magnetic signal denoted as S1' =f 1 (x i ,y i H2).

[0022] In one possible implementation, S is calculated according to the following formula. 1 The corresponding observation point magnetic field function f 1 (x i ,y i Extension of H1 to the z = H2 plane:

[0023]

[0024] In the formula, x and y represent the coordinates of all points on the flight path of the UAV at a lower flight altitude; ξ and η represent the coordinates of all points on the flight path of the UAV at a higher flight altitude.

[0025] In one possible implementation, the data fusion is: combining the magnetic signal S detected by the UAV at a higher flight altitude 2 Subtract the updated magnetic signal S 1' Acquire magnetic anomaly detection signal S that does not contain the geomagnetic field. T .

[0026] In one possible implementation, the magnetic target detection algorithm includes an orthogonal basis decomposition detection algorithm or a minimum entropy detection algorithm.

[0027] According to another aspect of the present invention, a high- and low-altitude coordinated airborne magnetic detection system for underwater magnetic anomalies is proposed, the system comprising:

[0028] A magnetic signal acquisition module is configured to detect magnetic signals from a target at a known detection distance using two unmanned aerial vehicles (UAVs) equipped with magnetic anomaly detectors flying in coordination. The latitude and longitude of the two UAVs remain consistent at any time during flight, but their altitudes are inconsistent. The flight altitude of the two UAVs is less than the known detection distance. The magnetic signal is a magnetic signal free from magnetic interference.

[0029] The magnetic signal update module is configured to extend the magnetic signal detected by a UAV at a low flight altitude upward to the altitude corresponding to another UAV, thereby obtaining an updated magnetic signal.

[0030] The data fusion module is configured to fuse the updated magnetic signal with the magnetic signal detected by the UAV at a higher flight altitude to obtain a magnetic anomaly detection signal that does not contain the geomagnetic field; the data fusion is as follows: fusing the updated magnetic signal with the magnetic signal detected by the UAV at a higher flight altitude... 2 Subtract the updated magnetic signal S 1' Acquire magnetic anomaly detection signal S that does not contain the geomagnetic field. T ;

[0031] A target detection module configured to use a magnetic target detection algorithm to judge the magnetic anomaly detection signal without the geomagnetic field, so as to determine whether the target to be measured is a weak magnetic target.

[0032] In one possible implementation, the magnetic signal updating module performs upward continuation processing on the magnetic signals detected by the UAV with a lower flight altitude to the altitude corresponding to another UAV, and the obtained updated magnetic signals include:

[0033] The magnetic signal detected by the UAV with a lower flight altitude is denoted as S 1 , and the magnetic signal detected by the UAV with a higher flight altitude is denoted as S 2 , S 1 , S 2 is a point corresponding to the aircraft trajectory, denoted as:

[0034]

[0035]

[0036] where N represents N points on the trajectory; As the output of the function f(x, y, z) representing the magnetic field at the observation point:

[0037]

[0038]

[0039] x i , y i are the coordinates of the observation point, H1 and H2 are the flight altitudes of the dual UAVs, and H1 < H2;

[0040] According to the output of the function f 1 of the magnetic field at the observation point corresponding to S 1 (x i , y i , H1), calculate its extension to the plane z = H2, and the obtained updated magnetic signal is denoted as S 1' = f 1 (x i , y i , H2).

[0041] In one possible implementation, the magnetic signal updating module calculates the extension of the function f 1 of the magnetic field at the observation point corresponding to S 1 (x i , y i to the plane z = H2 according to the following formula:

[0042]

[0043] In the formula, x and y represent the coordinates of all points on the flight path of the UAV at a lower flight altitude; ξ and η represent the coordinates of all points on the flight path of the UAV at a higher flight altitude.

[0044] The beneficial technical effects of this invention are:

[0045] This invention proposes a high-low altitude coordinated airborne magnetic detection method and system for underwater magnetic anomaly targets. For a target at a known detection range, two unmanned aerial vehicles (UAVs) equipped with magnetic anomaly detectors cooperate to detect magnetic signals. The latitude and longitude of the two UAVs remain consistent at all times during flight, while their altitudes differ. The magnetic signal detected by the UAV at the lower altitude is extended upwards to the altitude corresponding to the other UAV, obtaining an updated magnetic signal. This updated magnetic signal is then fused with the magnetic signal detected by the UAV at the higher altitude to obtain a magnetic anomaly detection signal that does not contain the Earth's magnetic field. A magnetic target detection algorithm is used to evaluate this magnetic anomaly detection signal to determine whether the target is a weak magnetic target. This invention, through its specialized flight method and data fusion algorithm design, can quickly remove the obscuring effect of the Earth's magnetic field on the weak magnetic target signal, eliminating the need for post-processing of the measured magnetic field. It is simple, fast, and real-time. Attached Figure Description

[0046] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0047] Figure 1 This is a flowchart of a high- and low-altitude coordinated airborne magnetic detection method for underwater magnetic anomaly targets, as described in an embodiment of the present invention.

[0048] Figure 2 This is an example diagram illustrating an application scenario in an embodiment of the present invention.

[0049] Figure 3 This is another flowchart of a high- and low-altitude coordinated airborne magnetic detection method for underwater magnetic anomaly targets according to an embodiment of the present invention.

[0050] Figure 4 This is an example diagram illustrating the process of constructing a magnetic background field in an embodiment of the present invention.

[0051] Figure 5 This is an example diagram illustrating the process of simulating the magnetic field of a weak magnetic target in an embodiment of the present invention.

[0052] Figure 6 This is an example diagram showing the results of detecting weak magnetic targets using the method of the present invention in an embodiment of the present invention.

[0053] Figure 7 This is a schematic diagram of the structure of a high- and low-altitude coordinated airborne magnetic detection system for underwater magnetic anomalies, as described in an embodiment of the present invention. Detailed Implementation

[0054] The principles and spirit of the invention will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are given merely to enable those skilled in the art to better understand and implement the invention, and are not intended to limit the scope of the invention in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of this disclosure to those skilled in the art.

[0055] Those skilled in the art will recognize that embodiments of the present invention can be implemented as a system, apparatus, device, method, or computer program product. Therefore, this disclosure can be specifically implemented in the following forms: entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software. It should be understood herein that any number of elements in the accompanying drawings is for illustrative purposes only and not as a limitation, and any naming is for distinction only and has no limiting meaning.

[0056] The purpose of this invention is to accurately, rapidly, and conveniently detect weakly magnetic targets underwater or underground. Therefore, this invention proposes a high- and low-altitude coordinated airborne magnetic detection method and system for underwater magnetic anomaly targets. First, a dynamic detection array is constructed, consisting of two unmanned aerial vehicles (UAVs) equipped with magnetic anomaly detectors (optically pumped magnetometers). The two UAVs maintain a dynamic detection process along a planned route. Then, based on geomagnetic field extension technology, a geomagnetic field estimation equation is established, providing the process of removing the geomagnetic field from the magnetic field signals of the two UAVs. The signal after removing the geomagnetic field from the output of the optically pumped magnetometer is used for target detection.

[0057] This invention provides a high- and low-altitude coordinated airborne magnetic detection method for underwater magnetic anomaly targets, such as... Figure 1 As shown, the method includes the following steps:

[0058] Step 1: For the target with a known detection range, use two UAVs equipped with magnetic anomaly detectors to conduct magnetic signal detection through coordinated flight; the latitude and longitude of the two UAVs remain consistent at any time during flight, but their altitudes are inconsistent;

[0059] Step 2: Extend the magnetic signal detected by the UAV at a lower flight altitude upward to the altitude corresponding to another UAV to obtain an updated magnetic signal;

[0060] Step 3: Perform data fusion on the updated magnetic signal and the magnetic signal detected by the drone with a higher flight altitude to obtain a magnetic anomaly detection signal that does not contain the geomagnetic field;

[0061] Step 4: Use a magnetic target detection algorithm to judge the magnetic anomaly detection signal that does not contain the geomagnetic field to determine whether the待测 target is a weak magnetic target.

[0062] The method starts from Step 1. In Step 1, for a待测 target with a known detection distance, use two drones equipped with magnetic anomaly detectors to fly in coordination for magnetic signal detection.

[0063] According to an embodiment of the present invention, a magnetic anomaly detector (optical pumping magnetometer) is installed on the two drones. The magnetic anomaly detector has a compensation function for the magnetic interference of its own drone, and the output magnetic signal is a magnetic signal that does not contain platform magnetic interference. Let the two drones fly in coordination for detection, keep the flight tracks consistent, the heights inconsistent, and fly along a certain direction for line measurement, that is, drone 1 flies along a line at a height of H1, and drone 2 flies along a line at a height of H2; the latitudes and longitudes of the two aircraft are kept consistent at any time, and the magnetic anomaly detection device synchronously outputs the magnetic signals S 1 , S 2 to the data processing terminal.

[0064] It should be noted that the detection distance D of the weak magnetic target to be measured and the magnetic anomaly detection system for this weak magnetic target should be known; ensure that the height of drone 1 in the two drones is less than the height of drone 2, that is, H1 < H2; ensure that the trajectories of drone 1 and drone 2 are the same at the same time; the distance between drone 2 at a higher flight altitude and the weak magnetic target to be measured is less than its detection distance D, that is, S 2 must contain the target signal, but it cannot be detected due to the influence of the geomagnetic field.

[0065] Specifically, as Figure 2 shown, assume that the flight trajectory set of drone 1 is The flight trajectory set of drone 2 is Since the two drones maintain the same speed and direction, the sets P 1 , P 2 both have a length of N. Each element in the trajectory set is described by three-dimensional positions in space. Since the two drones only have different flight heights, the trajectories can be described as follows:

[0066]

[0067]

[0068] To ensure that both unmanned aerial vehicles (UAVs) can detect the target signal, H2 < D, where D represents the detection distance of the magnetic anomaly detector for the detection target.

[0069] The magnetic field signal without platform magnetic interference output by the magnetic anomaly detector carried by UAV 1 is denoted as S 1 , and the magnetic field signal without platform magnetic interference output by the magnetic anomaly detector carried by UAV 2 is denoted as S 2 . S 1 , S 2 is the point corresponding to the aircraft trajectory, so the length of S 1 , S 2 is also N. It can be described as:

[0070]

[0071]

[0072] Then perform step two. In step two, the magnetic signal detected by the UAV with a lower flight altitude is upward continued to the altitude corresponding to the other UAV to obtain the updated magnetic signal.

[0073] According to the embodiment of the present invention, it can be used as the output of the function f(x, y, z) representing the magnetic field at the observation point:

[0074]

[0075]

[0076] According to the output of S 1 , calculate f 1 (x i , y i , H1) extended to the plane z = H2:

[0077]

[0078] In the formula, x and y represent the coordinates of all points on the flight trajectory of the UAV with a lower flight altitude; ξ and η represent the coordinates of all points on the flight trajectory of the UAV with a higher flight altitude. Here, x i , y i are not used to represent because the acquisition points are sparser. In the formula, x, y, ξ, and η represent infinitely many points on the trajectory, and x i , y i are just partial samplings of x, y, ξ, and η.

[0079] Use a suitable method (such as the piecewise integration method, algebraic surface integral method, frequency domain integral method, etc.) to calculate the integral in the above formula, and the result obtained is denoted as S1' That is, the updated magnetic signal, and S 1' With S 1 and S 2 Equal length, S 1' Represented as:

[0080] S 1' =f 1 (x i ,y i H2)

[0081] Then proceed to step three. In step three, the updated magnetic signal is fused with the magnetic signal detected by the UAV at a higher flight altitude to obtain a magnetic anomaly detection signal that does not contain the Earth's magnetic field.

[0082] According to an embodiment of the present invention, the magnetic field extrapolation process can obtain anomalies with different spectral components, i.e., extract anomalies at different depths. The result S after extrapolation 1' Since information about nearby weak magnetic targets is lost, it can be represented as the influence of the geomagnetic field at height H2. Deep magnetic sources have stronger magnetism and are located at greater distances, while shallow magnetic sources have weaker magnetism and are located at closer distances. And deep magnetic sources at S... 1 As shown in the figure, through the continuation method, it can be approximately regarded as the deep magnetic source originating from S. 2 This is reflected in the text. However, shallow magnetic sources in S... 1 As shown in the diagram, after the continuation method, it approximates 0. Therefore, S 2 -S 1' It can be used to represent the magnetic field characteristics of shallow magnetic sources.

[0083] Therefore, let S 2 -S 1' This indicates that the signal S contains magnetic anomaly characteristics 2 The process of removing the influence of the geomagnetic field. The process from continuation to data subtraction can be called S... 1 ,S 2 The process of data fusion, and the result of data fusion are represented as S. T :

[0084] S T =S 2 -S 1'

[0085] Finally, step four is executed. In step four, a magnetic target detection algorithm is used to judge the magnetic anomaly detection signal that does not contain the geomagnetic field, in order to determine whether the target to be tested is a weak magnetic target.

[0086] According to an embodiment of the present invention, it is assumed that S is obtained throughout the entire measurement process. 1 ,S 2 If the process does not include diurnal magnetic interference and other external magnetic interference, then ST This is represented as a magnetic field containing only the characteristics of the weakly magnetic target to be measured. Let S... T For target signal detection algorithms, information about the measured line segment S can be obtained. 1 ,S 2 The conclusion is whether the target contains a magnetic target. The magnetic target detection algorithm can be an orthogonal basis decomposition detection algorithm or a minimum entropy detection algorithm.

[0087] As an example, such as Figure 3 As shown, the process flow of the method described in this embodiment is as follows:

[0088] A magnetic anomaly detector (optically pumped magnetometer) is mounted on the two drones. The magnetic anomaly detector has a compensation function for the magnetic interference of its own drones, and the output magnetic signal is a magnetic signal that does not contain the platform's magnetic interference.

[0089] Two unmanned aerial vehicles (UAVs) are instructed to conduct collaborative flight surveys, maintaining consistent flight paths but different altitudes, flying along a survey line in a specific direction. Specifically, UAV 1 maintains a survey line at altitude H1, while UAV 2 maintains a survey line at altitude H2. The latitude and longitude of both aircraft remain consistent at all times, and a platform-free magnetic signal S is synchronously output via a magnetic anomaly detection device. 1 ,S 2 To the data processing terminal;

[0090] The magnetic signal S returned by the UAV at an altitude of H1 (i.e., the lower altitude layer) 1 The data is then extended upwards to height H2 to obtain the extended high-height layer data, which is the updated magnetic signal S. 1' ;

[0091] The signal S is obtained by subtracting the data extended from the low-altitude layer from the high-altitude layer data. 1' The magnetic signal S returned by the UAV at an altitude of H1 2 Data fusion was performed to obtain the magnetic anomaly detection signal S, which does not include the geomagnetic field. T ;

[0092] For S T Use object detection algorithms to determine S T Whether the target contains the magnetic anomaly to be tested, thus enabling the detection of weak magnetic targets.

[0093] This invention proposes a high- and low-altitude coordinated detection method for underwater weak magnetic anomalies, and introduces the high- and low-altitude data coordinated processing method in the system. After high- and low-altitude coordinated data processing according to this invention, the detection probability of underwater magnetic anomalies can be improved. Through a specialized flight method and data fusion algorithm design, this invention can quickly remove the obscuring effect of the geomagnetic field on the weak magnetic target signal, eliminating the need for post-processing of the measured magnetic field, making it simple, fast, and real-time.

[0094] The technical effects of the present invention were further verified through experiments.

[0095] The experiment was conducted using simulation methods. Data was constructed by simulating the geomagnetic field and the magnetic anomaly field of the simulated weak magnetic target. The distance of the implementation of the present invention was explained through the experimental process.

[0096] Assume a geomagnetic field is constructed using a geomagnetic model and a magnetic dipole model to simulate a real geomagnetic environment. The simulated geomagnetic field area is 50km × 50km in size, and two drones fly at altitudes of 300 meters and 400 meters, respectively. A geological anomaly layer 3000 meters underwater contains a large amount of iron ore and other components; in the simulation, 40 magnetic dipoles are used to simulate this, ensuring that the magnetic anomaly detection equipment is still affected by it at flight altitudes of 300 meters and 400 meters.

[0097] Figure 4 To illustrate the process of constructing the magnetic background field, subplots (a) and (b) represent the geomagnetic source magnetic field within the 300-meter and 400-meter height layers, obtained using the IGRF model. Subplots (c) and (d) show the results after superimposing the simulated geological anomaly magnetic field with 40 magnetic dipoles onto subplots (a) and (b). The positions of the 40 magnetic dipoles are marked in subplots (c) and (d).

[0098] Within this region, the target magnetic field is simulated. Figure 5 The process of simulating the magnetic field of a weak magnetic target is described. At position 1, 50 meters underwater, in subfigures (a) and (b), the magnetic field of the weak magnetic target is generated by simulating the magnetic field of a magnetic dipole. Subfigures (a) and (b) show that the weak magnetic target is difficult to detect against the geomagnetic background. The diagonals in subfigures (a) and (b) represent the flight trajectories of the two designed aircraft. In subfigure (a), the output of the magnetic anomaly detection device is the magnetic field value dynamically measured at all locations during flight at an altitude of 300 meters; in subfigure (b), the output is the magnetic field value measured at all locations during flight at an altitude of 400 meters; subfigure (c) shows the original magnetic field signals output by the two aircraft, which include the geomagnetic field and the weak magnetic target anomaly field. The dashed box in the figure indicates the position of the set magnetic dipole. It can be seen that in the original magnetic field output, the magnetic anomaly field of the weak magnetic target is difficult to identify against the background of the geomagnetic field. Subgraph (d) represents the magnetic field signal after processing with filtering techniques commonly used in target detection algorithms. The filtering frequency band is @0.025-0.12Hz. The area within the dashed box is the signal location of the magnetic anomaly field. In the filtered data, the magnetic anomaly target cannot be identified by the target detection algorithm.

[0099] Figure 6The results of weak magnetic target detection after the steps described in this invention are shown in sub-figure (a). The solid line in sub-figure (a) represents the original data output by the magnetic anomaly detector of the UAV at altitude H2, and the dashed line represents the result of magnetic field extension of the original data output by the magnetic anomaly detector of the UAV at altitude H1. The solid and dashed lines are almost identical; the difference between them is only noticeable after filtering. Sub-figure (b) shows the result of filtering the data in sub-figure (a), with a filtering frequency band of @0.025-0.12Hz. It can be seen that there is a difference between the solid and dashed lines in sub-figure (b) within the dashed box. This is because the extended data weakens the magnetic field of the magnetic target while preserving the Earth's magnetic field as much as possible. However, the signal in sub-figure (b) is still difficult to detect, and it is difficult to find magnetic targets in the data. Sub-figure (c) shows the data fusion result S in this invention. T It can be seen that the magnetic anomaly signal within the dashed box differs significantly from the signals in other parts, indicating it is no longer affected by the magnetic field. The data fusion result S T Common target detection methods have been used to detect and locate the magnetic anomaly target, thus verifying the feasibility of the high-low altitude coordinated airborne magnetic detection method for underwater magnetic anomaly targets described in this invention.

[0100] Another embodiment of the present invention provides a high- and low-altitude coordinated airborne magnetic detection system for underwater magnetic anomaly targets, such as... Figure 7 As shown, the system includes:

[0101] The magnetic signal acquisition module 710 is configured to detect magnetic signals from a target at a known detection distance using two unmanned aerial vehicles (UAVs) equipped with magnetic anomaly detectors flying in coordination. The latitude and longitude of the two UAVs remain consistent at any time during flight, but their altitudes are inconsistent. The flight altitude of the two UAVs is less than the known detection distance. The magnetic signal is a magnetic signal that does not contain magnetic interference.

[0102] The magnetic signal update module 720 is configured to extend the magnetic signal detected by the UAV at a low flight altitude upward to the altitude corresponding to another UAV, and obtain the updated magnetic signal.

[0103] The data fusion module 730 is configured to fuse the updated magnetic signal with the magnetic signal detected by the UAV at a higher flight altitude to obtain a magnetic anomaly detection signal that does not contain the geomagnetic field; the data fusion is as follows: fusing the updated magnetic signal with the magnetic signal detected by the UAV at a higher flight altitude... 2 Subtract the updated magnetic signal S 1' Acquire magnetic anomaly detection signal S that does not contain the geomagnetic field. T ;

[0104] A target detection module 740, configured to use a magnetic target detection algorithm to judge the magnetic anomaly detection signal without the geomagnetic field, so as to determine whether the target to be detected is a weak magnetic target.

[0105] In this embodiment, preferably, in the magnetic signal update module 720, the magnetic signal detected by the UAV with a lower flight altitude is upward continued to the altitude corresponding to another UAV, and the updated magnetic signal obtained includes:

[0106] The magnetic signal detected by the UAV with a lower flight altitude is denoted as S 1 , and the magnetic signal detected by the UAV with a higher flight altitude is denoted as S 2 , S 1 , S 2 is a point corresponding to the aircraft trajectory, denoted as:

[0107]

[0108]

[0109] where N represents N points on the trajectory; As the output of the function f(x, y, z) representing the magnetic field at the observation point:

[0110]

[0111]

[0112] x i , y i are the coordinates of the observation point, H1 and H2 are the flight altitudes of the dual UAVs, and H1 < H2;

[0113] According to the output of the observation point magnetic field function f 1 corresponding to S 1 (x i , y i , H1), calculate its extension to the plane z = H2, and the updated magnetic signal is denoted as S 1' = f 1 (x i , y i , H2).

[0114] In this embodiment, preferably, in the magnetic signal update module 720, the extension of the observation point magnetic field function f 1 corresponding to S 1 (x i , y i , H1) to the plane z = H2 is calculated according to the following formula:

[0115]

[0116] In the formula, x and y represent the coordinates of all points on the flight path of the UAV at a lower flight altitude; ξ and η represent the coordinates of all points on the flight path of the UAV at a higher flight altitude.

[0117] For the undescribed parts of the high- and low-altitude coordinated airborne magnetic detection system for underwater magnetic anomalies according to an embodiment of the present invention, please refer to the detailed description of the method embodiment above.

[0118] It should be noted that although several units, modules, or sub-modules are mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0119] Furthermore, although the operations of the method of the present invention are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0120] While the spirit and principles of the invention have been described with reference to several specific embodiments, it should be understood that the invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that features in these aspects cannot be combined for benefit; such division is merely for ease of description. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for high- and low-altitude coordinated airborne magnetic detection of underwater magnetic anomaly targets, characterized in that, Includes the following steps: For a target with a known detection range, two unmanned aerial vehicles (UAVs) equipped with magnetic anomaly detectors are used to conduct magnetic signal detection through coordinated flight; the latitude and longitude of the two UAVs remain consistent at any time during flight, but their altitudes are inconsistent; The magnetic signal detected by a low-flying UAV is extended upwards to the altitude corresponding to another UAV to obtain an updated magnetic signal; including: The magnetic signals detected by low-flying drones are represented as The magnetic signals detected by high-flying drones are represented as , The point corresponding to the aircraft's trajectory is represented as: ； ； Where N represents the N points on the trajectory; As a function representing the magnetic field at the observation point Output: ； ； Here are the coordinates of the observation point. , For the flight altitude of the two drones, ; according to Corresponding observation point magnetic field function The output is used to calculate its direction. The planar extension yields the updated magnetic signal, represented as follows: ; calculate according to the following formula Corresponding observation point magnetic field function Towards Planar extension: ； In the formula, , Represents the coordinates of all points on the flight path of a low-flying drone; This represents the coordinates of all points on the flight path of a high-altitude drone. The updated magnetic signal is fused with the magnetic signal detected by a high-altitude UAV to obtain a magnetic anomaly detection signal that does not contain the Earth's magnetic field; the data fusion involves: combining the magnetic signal detected by the high-altitude UAV... Subtract the updated magnetic signal Obtain magnetic anomaly detection signals that do not contain the Earth's magnetic field. ; The magnetic anomaly detection signal that does not contain the geomagnetic field is detected using a magnetic target detection algorithm. A judgment is made to determine whether the target to be tested is a weak magnetic target.

2. The method for high- and low-altitude coordinated airborne magnetic detection of underwater magnetic anomaly targets according to claim 1, characterized in that, The flight altitude of the two unmanned aerial vehicles is less than the known detection distance.

3. The method for high- and low-altitude coordinated airborne magnetic detection of underwater magnetic anomaly targets according to claim 1, characterized in that, The magnetic signal is a magnetic signal that does not contain magnetic interference.

4. The method for high- and low-altitude coordinated airborne magnetic detection of underwater magnetic anomaly targets according to claim 1, characterized in that, The magnetic target detection algorithm includes an orthogonal basis decomposition detection algorithm or a minimum entropy detection algorithm.

5. A high- and low-altitude coordinated airborne magnetic detection system for underwater magnetic anomalies, characterized in that, include: A magnetic signal acquisition module is configured to detect magnetic signals from a target at a known detection distance using two unmanned aerial vehicles (UAVs) equipped with magnetic anomaly detectors flying in coordination. The latitude and longitude of the two UAVs remain consistent at any time during flight, but their altitudes are inconsistent. The flight altitude of the two UAVs is less than the known detection distance. The magnetic signal is a magnetic signal free from magnetic interference. A magnetic signal update module is configured to extend the magnetic signal detected by a low-flying UAV upwards to the altitude corresponding to another UAV, thereby obtaining an updated magnetic signal; including: The magnetic signals detected by low-flying drones are represented as The magnetic signals detected by high-flying drones are represented as , The point corresponding to the aircraft's trajectory is represented as: ； ； Where N represents the N points on the trajectory; As a function representing the magnetic field at the observation point Output: ； ； Here are the coordinates of the observation point. , For the flight altitude of the two drones, ; according to Corresponding observation point magnetic field function The output is used to calculate its direction. The planar extension yields the updated magnetic signal, represented as follows: ; calculate according to the following formula Corresponding observation point magnetic field function Towards Planar extension: ； In the formula, , Represents the coordinates of all points on the flight path of a low-flying drone; This represents the coordinates of all points on the flight path of a high-altitude drone. The data fusion module is configured to fuse the updated magnetic signal with the magnetic signal detected by the high-altitude UAV to obtain a magnetic anomaly detection signal that does not contain the geomagnetic field; the data fusion involves fusing the magnetic signal detected by the high-altitude UAV with the magnetic signal detected by the UAV. Subtract the updated magnetic signal Obtain magnetic anomaly detection signals that do not contain the Earth's magnetic field. ; The target detection module is configured to use a magnetic target detection algorithm to judge the magnetic anomaly detection signal that does not contain the geomagnetic field, so as to determine whether the target to be tested is a weak magnetic target.

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