Magnetic Detection Method and Device for Unexploded ordnance

Abstract

This invention discloses a method and apparatus for magnetic detection of unexploded ordnance, comprising: acquiring three components of a magnetic field near the unexploded ordnance using an array sensor; sending the three components of the magnetic field to an information processing terminal; processing the three components of the magnetic field to obtain a magnetic gradient tensor; and determining the location of the unexploded ordnance based on the magnetic gradient tensor. This invention can achieve accurate detection of the location of unexploded ordnance.

Description

Technical Field

[0001] This invention relates to the field of magnetic detection, and more particularly to a method and apparatus for magnetic detection of unexploded ordnance. Background Technology

[0002] With the development and advancement of science and technology, magnetic detection technology is also undergoing innovation. From the initial total field detection technology to the later gradient field detection technology, and now to the magnetic gradient tensor field detection technology, magnetic detection technology has been continuously developing and progressing. As the passive detection technology most easily used by individual soldiers, magnetic detection technology has attracted much attention from scholars at home and abroad. Compared with traditional magnetic detection methods, the magnetic gradient tensor has higher spatial resolution, can detect more magnetic field information of magnetic anomaly sources, can adapt to more complex measurement environments, can provide richer target information, and is not easily affected by geomagnetic diurnal variations. It can be widely used in unexploded ordnance (UXO) detection, target motion tracking, radio frequency identification (RFID) tag positioning and navigation, endoscopic capsules, etc. Furthermore, with magnetic dipoles as magnetic sources, research on the corresponding magnetic gradient tensor has become mainstream in recent years. Summary of the Invention

[0003] The purpose of this invention is to provide a method and apparatus for magnetic detection of unexploded ordnance, aiming to solve the problem of magnetic detection of unexploded ordnance.

[0004] This invention provides a method for magnetic detection of unexploded ordnance, comprising:

[0005] S1. Collect the three components of the magnetic field near the unexploded ordnance using an array sensor;

[0006] S2. Send the three components of the magnetic field to the information processing terminal;

[0007] S3. The information processing terminal processes the three components of the magnetic field to obtain the magnetic gradient tensor.

[0008] S4. The information processing terminal determines the location of the unexploded ordnance based on the magnetic gradient tensor.

[0009] The present invention also provides a magnetic detection device for unexploded ordnance, comprising:

[0010] The sensor is used to collect the three components of the magnetic field near the unexploded ordnance and send the three components of the magnetic field to the information processing terminal;

[0011] The information processing terminal is used to receive the three components of the magnetic field sent by the sensor, process the three components of the magnetic field to obtain the magnetic gradient tensor, and determine the position of the unexploded ordnance based on the magnetic gradient tensor.

[0012] Using the embodiments of the present invention, it is possible to determine the location of an unexploded ordnance by means of a magnetic gradient tensor.

[0013] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a flowchart of the magnetic detection method for unexploded ordnance according to an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the detection site for the magnetic detection method for unexploded ordnance according to an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of the magnetic detection method for unexploded ordnance according to an embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram of the sensor space array structure of the magnetic gradient tensor system in the magnetic detection method for unexploded ordnance according to an embodiment of the present invention;

[0019] Figure 5 The existing technology calculates the magnetic field component B. xx Schematic diagram;

[0020] Figure 6 This is the calculation of the magnetic field component B in the unexploded ordnance magnetic detection method of this invention. xx Schematic diagram;

[0021] Figure 7 The third-order magnetic gradient tensor B of the unexploded ordnance magnetic detection method in this embodiment of the invention is shown in the single-pathway configuration. xx Schematic diagram comparing component values ​​with true values;

[0022] Figure 8 This is a schematic diagram of a five-sensor planar cross-shaped magnetic gradient tensor system in the prior art;

[0023] Figure 9 This is the first technology to use a five-sensor planar cross-shaped method to calculate the magnetic gradient tensor B. xxx Component diagram;

[0024] Figure 10 The present invention relates to an embodiment of the magnetic detection method for unexploded ordnance, which employs an eight-sensor planar cross-shaped method to calculate the magnetic gradient tensor B.xxx Component diagram;

[0025] Figure 11 The third-order magnetic gradient tensor B of the unexploded ordnance magnetic detection method in this embodiment of the invention is... xxx Schematic diagram comparing component values ​​with true values;

[0026] Figure 12 The third-order magnetic gradient tensor B, representing the increase in magnetic moment of the unexploded ordnance magnetic detection method according to this invention, is... xxx Schematic diagram comparing component values ​​with true values;

[0027] Figure 13 This is a schematic diagram of an unexploded ordnance magnetic detection device according to an embodiment of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Method Implementation Examples

[0030] According to an embodiment of the present invention, a method for magnetic detection of unexploded ordnance is provided. Figure 1 This is a flowchart of the magnetic detection method for unexploded ordnance according to an embodiment of the present invention, as follows: Figure 1 As shown, it specifically includes:

[0031] S1. Collect the three components of the magnetic field near the unexploded ordnance using an array sensor;

[0032] S1 specifically includes: acquiring the three components of the magnetic field through an eight-array triaxial fluxgate sensor.

[0033] S2. Send the three components of the magnetic field to the information processing terminal;

[0034] S2 specifically includes: transmitting the three components of the magnetic field to the information processing terminal via a transmission line.

[0035] S3. The information processing terminal processes the three components of the magnetic field to obtain the magnetic gradient tensor.

[0036] S3 specifically includes: the information processing terminal calculates the magnetic gradient tensor of the center point of the array sensor based on Taylor's formula, the central difference method, and the three components of the magnetic field.

[0037] The formula for the second-order magnetic gradient tensor is as follows:

[0038]

[0039] in, (a = x, y, z; b = 1, 2, 3, 4, 5, 6, 7, 8) represents the magnetic field component B measured by sensor b. a .

[0040] The third-order magnetic gradient tensor formula is as follows:

[0041]

[0042] in, (m = x, y, z; n = 1, 2, 3, 4, 5, 6, 7, 8) represents the magnetic field component B measured by sensor n. m , where (i,j) represents the specific coordinates of the measurement point.

[0043] S4. The information processing terminal determines the location of the unexploded ordnance based on the magnetic gradient tensor.

[0044] This invention proposes a stability optimization algorithm for magnetic gradient tensors and a corresponding sensor spatial array structure, which enhances the anti-interference capability of magnetic gradient tensor data and enables more accurate acquisition of target information under complex magnetic interference conditions.

[0045] The specific implementation method is as follows:

[0046] Figure 2 This is a schematic diagram of the detection site for the magnetic detection method for unexploded ordnance according to an embodiment of the present invention, as shown below. Figure 2 As shown:

[0047] When a magnetic anomaly is detected, the sensor transmits the data to the data acquisition card via a data transmission line. The data is then processed by the information processing terminal, and the results are obtained according to the corresponding algorithm.

[0048] Figure 3 This is a detailed schematic diagram of the magnetic detection method for unexploded ordnance according to an embodiment of the present invention, as shown below. Figure 3 As shown:

[0049] This includes: data acquisition, data transmission, data processing, inversion, and drawing conclusions;

[0050] 1 Data Collection

[0051] During data acquisition, it is essential to ensure that the spatial attitude of the detection device remains unchanged.

[0052] 2 Data Transmission

[0053] Ensure that the transmission distance is not too far and that the data transmission line used has anti-interference protection.

[0054] 3 Data Processing

[0055] The obtained data needs to undergo preliminary noise reduction.

[0056] 4. Conclusion

[0057] The results were initially screened, and those with large fluctuations were discarded.

[0058] 5. Data Analysis

[0059] The root mean square error and absolute error are usually used to evaluate the results.

[0060] Figure 4 This is a schematic diagram of the sensor spatial array structure of the magnetic gradient tensor system in the magnetic detection method for unexploded ordnance according to an embodiment of the present invention, as shown below. Figure 4 As shown, h = 0.1m, and all sensors are triaxial fluxgate sensors.

[0061] Second-order magnetic gradient tensor stability optimization method:

[0062] To improve the stability of the magnetic gradient tensor, an improved central difference method is proposed by combining (3-1) and Taylor expansion, as shown in Equation (3-1), and its error is shown in Equation (3-2).

[0063]

[0064]

[0065] Where L is the set of omitted terms. Combining formula (3-1) and Figure 4 The approximate calculation formulas for each component of the magnetic gradient tensor are as follows:

[0066]

[0067] in, (a = x, y, z; b = 1, 2, 3, 45, 6, 7, 8) represents the magnetic field component B measured by sensor b. a .

[0068] The traditional formula for calculating the magnetic gradient tensor is shown below:

[0069]

[0070] in, (m = x, y, z; n = 1, 2, 3, 4) represents the magnetic field component B measured by sensor n. m h = 0.1m.

[0071] Formula (3-4) is named Method 1, and formula (3-3) is named Method 2.

[0072] To verify the strong stability of Method 2, the following simulation experiments were conducted:

[0073] We define the background as follows: a magnetic dipole is a source of magnetic anomalies. Its spatial coordinates are (-1m, -2m, 0m), h = 0.1m. The magnetic moment responds to an external magnetic field, resulting in induced magnetization. The assumed magnetic dipole moment is a combination of induced and residual magnetization. The magnetic moment of the magnetic dipole is (100, 10, 10), assuming the Earth's magnetism is used as the background field and is a uniform magnetic field. The true values ​​used are obtained from formula (2-3). To avoid various noise reduction methods missing some useful information and causing deviations in the results, no noise reduction was performed on any simulation experiments; the superiority of the two methods was judged only by their stability.

[0074] Multi-path measurements were employed, with an x-axis range of -10m to 9.4m and a y-axis range of -9.4m to 9.4m. The measured plane was 0.1m high, and the measurement point spacing was 0.2m. Gaussian white noise with a mean of 0nT and a variance of 1nT was added to the readings of each sensor.

[0075] Figure 5 The existing technology calculates the magnetic field component B. xx Schematic diagram;

[0076] Figure 6 This is the calculation of the magnetic field component B in the unexploded ordnance magnetic detection method of this invention. xx Schematic diagram;

[0077] Figure 5 and Figure 6 The magnetic gradient tensor B is given. xx Component contour plots. We can see that, under the same noise conditions, Method 2 has more blank areas and less noise compared to Method 1. That is, under the same interference conditions, Method 2 causes fewer local data anomalies when disturbed. This indicates that Method 2 has more usable data, less data variation due to noise, and stronger stability.

[0078] To conduct a more intuitive comparison and verification, we performed the following simulation experiment:

[0079] (2) Figure 7 The third-order magnetic gradient tensor B of the unexploded ordnance magnetic detection method in this embodiment of the invention is shown in the single-pathway configuration. xx A diagram showing the comparison between components and the true value, as shown below. Figure 7 As shown:

[0080] A single-line measurement was conducted with y = -6m and x ranging from -10 to 9.4m. The height of the measurement plane was 0.1m. The distance between measurement points was 0.2m. Gaussian white noise with a mean of 0nT and a variance of 1nT was added to the sensor readings. Method 2 was significantly superior to Method 1.

[0081] The root mean square error, also known as the standard error, is the square root of the ratio of the square of the deviation between the predicted and true values ​​to the number of observations, N. In actual measurements, the number of observations, n, is always finite, and the true value can only be represented by the most reliable (best) value. The root mean square error is highly sensitive to the maximum or minimum errors in a set of measurement data, therefore, it can well reflect the precision of the measurement. This is precisely why the root mean square error is widely used in engineering surveying. The standard deviation measures the dispersion of a set of numbers, while the root mean square error measures the deviation between the observed and true values. They have different research objects and purposes. This section uses the root mean square error to compare errors, and its calculation formula is shown in formula (3-5).

[0082]

[0083] Where, η r For the estimated value, η ei For true values, N represents the number of measurement points.

[0084] Table 1. Root mean square error of each component of the magnetic gradient tensor

[0085]

[0086] Third-order magnetic gradient tensor stability optimization method

[0087] Magnetic detection technology has seen rapid development in recent years due to its advantages such as low cost, low system attitude requirements, and high accuracy. Magnetic gradient tensors and related data interpretation methods are also attracting increasing attention from scholars in the field of magnetic detection. Notably, second-order and third-order magnetic gradient tensors are widely used in target localization and identification tasks. However, compared to second-order magnetic gradient tensors, third-order magnetic gradient tensors can provide more accurate information and stronger magnetic source resolution, making research on third-order magnetic gradient tensors particularly important.

[0088] However, in researching more accurate, faster, and more stable target localization, many scholars have failed to consider the problem of poor stability when calculating the various components of the tensor. This is especially true for third-order and higher magnetic gradient tensor data, which are highly sensitive and easily affected by noise interference, leading to distorted results. To address the poor stability of the third-order magnetic gradient component algorithm, this invention optimizes the original third-order magnetic gradient tensor measurement formula based on the second-order improved central difference method, enhancing its stability and making it adaptable to the complex battlefield environment under modern interference conditions. Building upon the localization method proposed by Yin et al., a new tensor measurement formula is substituted for optimization, and the optimized method is analyzed through simulation and field experiments.

[0089] There are two main types of contemporary magnetic gradient tensor systems: those based on superconducting magnetometers and those based on fluxgate magnetometers. Although the accuracy of superconducting magnetic gradient tensors is several orders of magnitude higher than that of fluxgate tensors, the latter is usually preferred due to its more complex equipment and higher cost requirements. This is because fluxgate magnetic gradient tensors are simpler to install and have lower operating costs.

[0090] Traditional planar cross-shaped magnetic gradient tensor measurement systems consist of five sensors. Figure 8 This is a schematic diagram of a five-sensor planar cross-shaped magnetic gradient tensor system in existing technology, such as... Figure 8 As shown:

[0091] The second-order central difference method is similar to the first-order central difference method; both use the differential operator of the function to sample and perform a difference approximation of the derivative.

[0092] Traditional five-sensor planar cross-shaped magnetic gradient tensor detection devices perform measurements based on the second-order central difference method, as shown in formula (4-1):

[0093]

[0094] From formula (4-1) and the Taylor expansion, we can see that the error is as shown in formula (4-2):

[0095]

[0096] Where L is the set of omitted terms. As can be seen from formula (4-2), the measurement formula for the traditional third-order magnetic gradient tensor has a second-order error.

[0097] To improve the measurement accuracy and stability of the third-order magnetic gradient tensor, the second-order central difference method is improved and combined with the magnetic gradient tensor detection device designed above. Figure 4 A new measurement principle formula for the third-order magnetic gradient tensor can be derived, as shown in formula (4-3):

[0098]

[0099] From formula (4-3) and the Taylor expansion, we can see that its error is as shown in formula (4-4):

[0100]

[0101] As can be seen from formulas (4-2) and (4-4), the error of the new measurement method is a fourth-order error, which is significantly smaller than the second-order error of the traditional measurement.

[0102] The third-order magnetic gradient tensor T consists of the spatial derivatives of nine second-order gradient tensor components along the x, y, and z directions. T has 27 components, of which 7 are independent. The components of T are as follows:

[0103]

[0104]

[0105]

[0106] According to the positioning method proposed by Yin et al., only six components, namely B, need to be measured. xxx B xyx B xzx B yxy B yyy B yzy This allows for the location of the target. Furthermore, according to formula (4-7), B... zzz B xzx B yzy Therefore, in actual measurement and calculation, B xxx B xyx B xzx B yxy B yyy B yzy Simply take the measurement.

[0107] according to Figure 8 As shown in formula (4-1), Δx takes the value 2h, and formula (4-1) can be rewritten as:

[0108]

[0109] Combination Figure 8 From formula (4-8), we can obtain the calculation formulas for the six components of the third-order magnetic gradient tensor when measuring a third-order magnetic gradient tensor system, as shown in formula (4-9):

[0110]

[0111] in, (m = x, y, z; n = 1, 2, 3, 4, 5) represents the magnetic field component B measured by sensor n. m , where (i,j) represents the specific coordinates of the measurement point.

[0112] Similar to formula (4-8), we can rewrite formula (4-1) as follows:

[0113]

[0114] Combining formula (4-10) and Figure 4Thus, the approximate calculation formula for the optimized third-order magnetic gradient tensor can be obtained, as shown in formula (4-11):

[0115]

[0116] in, (m = x, y, z; n = 1, 2, 3, 4, 5, 6, 7, 8) represents the magnetic field component B measured by sensor n. m , where (i,j) represents the specific coordinates of the measurement point.

[0117] Formula (4-9) is named Method 3, and formula (4-11) is named Method 4. To verify whether the optimized magnetic gradient tensor calculation method is more stable and less susceptible to noise interference, the following simulation experiments were conducted:

[0118] Experimental background:

[0119] The structure of the measurement system used is as follows: Figure 4 As shown, h = 0.1m. Assuming the magnetic dipole's spatial position is (0m, 0m, 0m), the preset magnetic dipole moment is a combination of the induced magnetization and the remanent magnetization, with a torque magnitude of 1000 A·m. 2 The geomagnetic background field is assumed to be a strong, uniform magnetic field. The magnetic dipole angle is 0°, and the magnetic tilt angle is 90°. A gridded measurement, i.e., multi-path measurement, is performed: the x-direction is from -9.6m to 9.6m, and the y-direction is from -9.6m to 9.6m. The measurement plane height is 1m, and the point spacing is 0.2m. In the simulation, the true values ​​of each component of the third-order magnetic gradient tensor are calculated using formula (2-5).

[0120] Experiment (1):

[0121] Gaussian white noise with a mean of 0 nT and a variance of 1 nT was added to the readings of each sensor. To obtain the true values ​​and reduce further errors caused by filtering and noise reduction, which could affect the observation results, no noise reduction was used. The components of the third-order magnetic gradient tensor obtained using methods 3 and 4 were obtained, and contour plots of each component were generated. (The last part, "B," appears to be a typo and can be omitted.) xxx For example,

[0122] Figure 9 This is the first technology to use a five-sensor planar cross-shaped method to calculate the magnetic gradient tensor B. xxx Component diagram;

[0123] Figure 10 The present invention relates to an embodiment of the magnetic detection method for unexploded ordnance, which employs an eight-sensor planar cross-shaped method to calculate the magnetic gradient tensor B. xxx Component diagram;

[0124] pass Figure 9 and Figure 10 It can be seen that, under noisy conditions, Method 4 has more blanks and less noise compared to Method 3. In other words, under the same interference conditions, Method 4 causes fewer local data anomalies when subjected to interference. This indicates that Method 4 has more usable data, less data variation due to noise, and stronger stability.

[0125] To more intuitively compare the stability of the two methods, the following two experiments were conducted:

[0126] Experiment (2):

[0127] Figure 11 The third-order magnetic gradient tensor B of the unexploded ordnance magnetic detection method in this embodiment of the invention is... xxx A schematic diagram comparing the components with the true value; Based on the data from experiment (1), the components of the third-order magnetic gradient tensor under a single path of x = -5.2m are plotted. By comparing the differences between the results obtained by the two methods and the true value, it is verified whether method 4 is better.

[0128] Experiment (3):

[0129] Figure 12 The third-order magnetic gradient tensor B, representing the increase in magnetic moment of the unexploded ordnance magnetic detection method according to this invention, is... xxx A diagram comparing the component values ​​with the true value; to enhance the impact of noise, the magnetic moment magnitude was changed to 100 A·m. 2 Gaussian white noise with a mean of 0 nT and a variance of 4 nT was added to the readings of each sensor. The curves of each component of the third-order magnetic gradient tensor were plotted along a path of x = -5.2 m. Through the above three simulation experiments, it was demonstrated that regardless of the magnitude or type of noise, the optimized third-order magnetic gradient tensor exhibits better stability and stronger anti-interference capability. This proves that the optimization method is superior under noise interference.

[0130] The beneficial effects of the invention are as follows:

[0131] (1) A new spatial array structure for magnetic detection equipment was designed and is small in size, making it easy to carry.

[0132] (2) The present invention uses an eight-sensor spatial array structure, which effectively matches the new second-order and third-order magnetic gradient tensor calculation formulas.

[0133] (3) The magnetic gradient tensor calculation method proposed in the invention has higher stability and stronger anti-interference ability under the same noise interference.

[0134] (4) Two new methods for calculating magnetic gradient tensors and corresponding spatial array structures for magnetic detection devices. The method is based on Taylor's formula and the central difference method, and uses the three components of the eight-point magnetic field to calculate the magnetic gradient tensor at the center point.

[0135] (5) When the present invention is used for detection, it can be applied to all methods that require the use of magnetic gradient tensor, and has universality and versatility.

[0136] (6) The present invention can effectively detect the values ​​of each component of the magnetic gradient tensor of the target at the detection point.

[0137] (7) This invention can be applied to the detection of magnetic targets under complex magnetic interference conditions.

[0138] Device Examples

[0139] According to an embodiment of the present invention, a magnetic detection device for unexploded ordnance is provided. Figure 13 This is a schematic diagram of an unexploded ordnance magnetic detection device according to an embodiment of the present invention, as shown below. Figure 13 As shown, it specifically includes:

[0140] The sensor is used to collect the three components of the magnetic field near the unexploded ordnance and send the three components of the magnetic field to the information processing terminal;

[0141] The information processing terminal is used to receive the three components of the magnetic field sent by the sensor, process the three components of the magnetic field to obtain the magnetic gradient tensor, and determine the position of the unexploded ordnance based on the magnetic gradient tensor.

[0142] The array sensor includes eight triaxial fluxgate sensors arranged in a cross shape, with two sensors on each side (top, bottom, left, and right). The top part includes a first sensor and a second sensor, with a spacing of H. The distance between the second sensor and the center point of the cross is also H. The array sensor is centrally symmetrical.

[0143] The sensor transmits the three components of the magnetic field to the information processing terminal via a transmission line.

[0144] The information processing terminal is specifically used to calculate the magnetic gradient tensor at the center point of the array sensor based on Taylor's formula, the central difference method, and the three components of the magnetic field.

[0145] The embodiments of the present invention are system embodiments corresponding to the above method embodiments. The specific operation of each module can be understood by referring to the description of the method embodiments, and will not be repeated here.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method of magnetic detection of unexploded ordnance, characterized by, The application relates to a method for detecting an unexploded bomb, and belongs to the field of unexploded bomb detection. S1, collecting three components of a magnetic field near an unexploded bomb through a center-symmetrical cross-shaped array composed of eight triaxial fluxgate sensors; wherein the center-symmetrical cross-shaped array is composed of two sensors in each of the up, down, left and right directions, the distance between a first sensor and a second sensor in the upper part is H, and the distance between the second sensor and a center point of the cross-shaped array is H; S2, sending the three components of the magnetic field to an information processing terminal; S3, the information processing terminal calculates second-order and third-order magnetic gradient tensors of the center point of the array according to a Taylor formula and an improved central difference method and using new second-order and third-order magnetic gradient tensor calculation formulas matched with the center-symmetrical cross-shaped array; The second-order magnetic gradient tensor calculation formula is as follows: wherein representing a magnetic field component measured by sensor b , a = x, y, z; b = 1, 2, 3, 4, 5, 6, 7, 8; The third-order magnetic gradient tensor calculation formula is as follows: wherein Bn represents a magnetic field component measured by sensor n m = x, y, z; n = 1, 2, 3, 4, 5, 6, 7, 8; Bn represents a magnetic field component measured by sensor n S4, the information processing terminal judges the position of the unexploded bomb according to the magnetic gradient tensors.

2. The method of claim 1, wherein, The S2 specifically comprises the following steps: sending the three components of the magnetic field to the information processing terminal through a transmission line.

3. An unexploded ordnance magnetic detection apparatus for performing the method of any one of claims 1 to 2, characterized in that, The application relates to a method for detecting an unexploded bomb, and belongs to the field of unexploded bomb detection. S1, collecting three components of a magnetic field near an unexploded bomb through a center-symmetrical cross-shaped array composed of eight triaxial fluxgate sensors; wherein the center-symmetrical cross-shaped array is composed of two sensors in each of the up, down, left and right directions, the distance between a first sensor and a second sensor in the upper part is H, and the distance between the second sensor and a center point of the cross-shaped array is H; S2, sending the three components of the magnetic field to an information processing terminal; 4. The apparatus of claim 3, wherein, S3, the information processing terminal calculates second-order and third-order magnetic gradient tensors of the center point of the array according to a Taylor formula and an improved central difference method and using new second-order and third-order magnetic gradient tensor calculation formulas matched with the center-symmetrical cross-shaped array; The second-order magnetic gradient tensor calculation formula is as follows: The third-order magnetic gradient tensor calculation formula is as follows: S4, the information processing terminal judges the position of the unexploded bomb according to the magnetic gradient tensors. The sensor module sends the three components of the magnetic field to the information processing terminal through a transmission line.

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