Method and device for detecting and positioning underground pipeline containing ferromagnetic material

Abstract

The invention discloses a method and a device for detecting and positioning an underground pipeline containing a ferromagnetic material. According to the invention, the fluxgate sensors and the position and attitude sensors are installed on the support frame, and the support frame is driven to rotate, so that rapid magnetic scanning measurement of the underground pipeline is realized, and the trend, the horizontal position and the depth of the pipeline are estimated. According to the invention, the efficiency is greatly improved by adopting a rotary scanning strategy, the problem of uneven or muddy ground is avoided, and the method is suitable for detecting a ferromagnetic target with a slender structure; the direction and depth of the pipeline are estimated by using the coordinates of the extreme points of the magnetic field, and the positions of ferromagnetic targets which are non-uniformly distributed along any straight line can be estimated; the method does not need an accurate magnetic field value, is suitable for a complex environment with strong interference, is short in estimation time, and supports real-time positioning of the pipeline; and the corresponding pipeline depth below each measurement node is estimated by using the measurement data of the plurality of measurement nodes at different heights, so that the method can be applied even if the pipeline is not horizontally buried.

Description

TECHNICAL FIELD

[0001] The present application relates to the underground pipeline magnetic detection technology of ferrous magnetic material, and particularly relates to a pipeline detection and positioning method of underground ferrous magnetic material and a device thereof. BACKGROUND

[0002] The damage of underground utilities (such as telecommunication, gas, television, water and sewer) can bring high economic losses, service interruption, gas leakage, sewage leakage and serious personnel injury or life danger and many other problems. With the acceleration of urbanization, the underground space is increasingly intensive, and the layout of communication cables, gas pipelines and water pipes and other facilities is complex, with different depths, materials and functions, which increases the difficulty of positioning and protection. Especially in old urban areas, the lack of accurate archives makes the risk of excavation damage higher.

[0003] The earth is distributed with stable magnetic field, and the ferromagnetic target can cause the change of the surrounding magnetic field. Since most pipelines contain ferromagnetic materials, the use of passive magnetic detection technology is a worthwhile exploration scheme because it is only sensitive to ferromagnetic materials and has nothing to do with water and other materials without ferromagnetic materials.

[0004] In 2015, Liu et al. used the magnetic dipole reconstruction (MDR) method to forward model the magnetic anomaly caused by underground ferromagnetic pipelines in the article "Forward modeling of total magnetic anomaly over a pseudo-2D underground ferromagnetic pipeline". To speed up and improve the accuracy of these calculations, they proposed a new segmentation strategy in the article "A new segmentation strategy for processing magnetic anomaly detection data of shallow depth ferromagnetic pipeline". Another forward modeling method is to calculate the magnetic anomaly of ferromagnetic pipelines based on the Poisson equation that describes the relationship between gravity and magnetic fields. Li et al. analyzed the characteristics of gravity and magnetic anomaly curves of parallel pipelines in "The effect of parallel pipeline parameters on the characteristics of gravity and magnetic surveys", while Sun et al. used deep learning neural networks to extract the magnetic anomaly of individual pipelines in "Magnetic anomaly detection of adjacent parallel pipelines using deep learning neural networks". Based on these forward modeling models, Wu Pan applied the AM-PSO algorithm to invert the parameters and buried depth of underground pipelines in "High-Precision Inversion of Buried Depth in Urban Underground Iron Pipelines Based on AM-PSO Algorithm for Magnetic Anomaly". In addition, Li et al. developed a buried pipeline positioning method based on magnetic data in "The positioning of buried pipelines from magnetic data", which combines inclination angle analysis and downward continuation.

[0005] It is worth noting that these methods rely on a key assumption that the ferromagnetic pipeline is uniformly magnetized by the Earth's magnetic field. However, due to factors such as pipeline manufacturing processes and complex magnetic field environments, the magnetic moment of the pipeline is not uniformly distributed. This makes it challenging to accurately and efficiently calculate the magnetic anomaly distribution of the pipeline. In addition, these inversion methods are computationally complex and time-consuming, making it difficult to provide real-time pipeline location information at the excavation site. SUMMARY

[0006] In view of the above problems of the prior art, the present application provides a pipeline detection and positioning method for underground pipelines containing ferromagnetic materials.

[0007] An object of the present application is to provide a pipeline detection and positioning method for underground pipelines containing ferromagnetic materials.

[0008] The pipeline detection and positioning method for underground pipelines containing ferromagnetic materials comprises the following steps:

[0009] 1) Pipeline detection and positioning device

[0010] The rotating support comprises a support frame, a rotating disc, a horizontal rod and a measurement node; the rotating disc is arranged at the top end of the support frame and is adjustable in height along the support frame; the center of the horizontal rod is arranged at the center of the rotating disc; one or more measurement nodes are arranged on the horizontal rod, and the distances from each measurement node to the center of the horizontal rod are different, thereby forming a measurement node array; each measurement node comprises a data acquisition module, a wireless communication module and a sensor module; the sensor module is connected to the data acquisition module, and the data acquisition module is connected to the wireless communication module; the sensor module comprises a fluxgate sensor and a position and attitude sensor.

[0011] The rotating disc is connected to a motor.

[0012] The measurement data of the measurement node is transmitted to a computer for processing through the wireless communication module.

[0013] 2) Rotating magnetic field measurement

[0014] A right-hand coordinate system is established; the motor drives the measurement node array on the horizontal rod to rotate around the vertical axis in the horizontal plane, and the measurement node array can perform 360° omnidirectional scanning in the horizontal direction to realize rapid magnetic anomaly scanning measurement of the underground pipeline.

[0015] 3) Estimation of the horizontal position and strike angle of the pipeline

[0016] The measurement node array is driven to rotate in the horizontal plane at a fixed height; the sensor module transmits the magnetic field at the measurement node and the position and attitude information to the data acquisition module, which is collected and transmitted to the computer through the wireless communication module; the computer extracts the position information of the measurement node when the magnetic field extreme point appears, and sets the position where the magnetic field extreme point appears as a candidate point of the suspected pipeline; then all the candidate points of the suspected pipeline are fitted into a straight line to obtain the horizontal position and strike angle of the pipeline.

[0017] 4) Depth estimation of the pipeline:

[0018] Adjust the height of the array of measurement nodes, and perform rotational measurement at different height positions from the ground in turn; select one or more measurement nodes at will, and obtain the total magnetic field response of the selected measurement nodes at each height, respectively; and then estimate the depth of the underground pipeline by analyzing the relationship between the total magnetic field response at each height and the corresponding height.

[0019] In step 1), the support frame, the rotating disc and the horizontal rod are made of non-magnetic materials. The length of the horizontal rod is as long as possible to facilitate operation, and the longer the horizontal rod, the larger the measurement range, about 4m; the speed at which the rotating disc drives the horizontal rod to rotate does not matter, and it is best to rotate at a constant speed for measurement.

[0020] The number of measurement nodes can be as few as one in principle, and multiple nodes are used to increase accuracy and reliability. Because the sensor used in the present application is low-cost, the data may not be very stable. Generally, 3-4 nodes can ensure stable data; if the horizontal rod is very long, more nodes can be used, and the more nodes, the larger the area to be detected, and the faster the detection task in the specified area can be completed.

[0021] Further, the measurement node further comprises a battery pack, which provides working voltage for the data acquisition module, the wireless communication module and the sensor module of the measurement node.

[0022] The real-time position and attitude information of each measurement node is obtained by the position and attitude sensor, the magnetic flux gate sensor acquires the magnetic field information, the data acquisition module acquires these information and transmits them to the computer, and the computer uses the position and attitude information to unify the measurement value of the magnetic flux gate sensor in the measurement node body coordinate system to the geographic coordinate system; further, it further comprises a real-time dynamic measurement reference station, which is stationary, and it works with the position and attitude sensor in all movable measurement nodes to improve the position measurement accuracy to centimeter level. If the reference station is not used, the accuracy can only reach meter level.

[0023] In step 2), the X-axis points to the north, the Y-axis points to the east, and the Z-axis points downward. Let (x, y, z) represent the spatial coordinates of the measurement node, and (x0, y0, z0) represent the center point of the pipeline. The pipeline is buried at a depth d underground, and the pipeline direction angle is χ (relative to the geographic north, clockwise is positive), and the minimum horizontal distance from the rotation center to the pipeline is p.

[0024] Compared with the traditional parallel movement measurement method, the rotation scanning strategy greatly improves the efficiency and avoids the problem of difficult movement due to uneven ground or mud, and is particularly suitable for detecting magnetic targets of elongated structures. In actual operation, the horizontal rod is installed on a rotating platform with controllable rotation function, and the platform is driven to rotate around the vertical axis by a motor. The measurement node array can perform 360° omnidirectional scanning on the detection area in the horizontal direction.

[0025] In step 3), when there is a ferromagnetic pipeline underground, the time series of magnetic fields collected by the rotating measurement node array usually presents periodic changes, and the positions of the significant extreme points correspond to the positions close to the top of the pipeline during the rotation of the measurement node. The periodic changes correspond to the number of rotation circles of the measurement node, and by recording the rotation angle corresponding to the extreme points, the general direction of the underground pipeline can be quickly inferred.

[0026] The coordinates of all suspected pipeline candidate points are V = {(x1, y1), (x2, y2), …, (x C ,y C )}, where (x j ,y j ) is the plane coordinate of the jth candidate point, j = 1, …, C, C is the number of candidate points; based on the least squares method, the best fitting straight line y = ax + b is found, where a is the slope and b is the intercept. The slope a and the intercept b are determined by the standard linear regression method under the condition of minimizing the sum of squared errors:

[0027]

[0028] The final straight line is the direction angle of the pipeline The center coordinates of the pipeline are and the minimum horizontal distance from the rotation center to the pipeline The quality of linear fitting can be evaluated by the determination coefficient R 2 , which is defined as follows:

[0029]

[0030] where, represents the y j value predicted by the fitted straight line, is the average value of the observed values. The value of R 2 ranges from 0 to 1, and the closer the value is to 1, the better the fitting effect.

[0031] In step 4), to estimate the depth of the pipe, rotational measurements are typically performed at 3 to 4 different heights. The detectable pipe depth depends on the strength of the pipe's magnetism. Generally, if the pipe depth is less than 4 meters, measurements at 3 different heights are sufficient, with a height interval of 20-50 centimeters. This interval is not strictly required and is approximately 1 / 10 of the estimated pipe burial depth.

[0032] Total magnetic field response ΔT of the pipeline i Defined as the absolute value of the difference between the total magnetic field extremum at the i-th altitude and the background geomagnetic field:

[0033]

[0034] in, This represents the total magnetic field extremum recorded at the i-th height by the measurement node. In practice, the magnetic field extremum of each rotation is usually extracted after multiple rotations and averaged to obtain the total magnetic field extremum for a stable estimate. The total magnetic field extremum appears in the same location at different heights, but the magnitude of the total magnetic field extremum is different; T geo The background total magnetic field value output by this measurement node is typically the average total field value measured by this node in the area without pipe influence. This is achieved by analyzing the absolute value |ΔT| of the total magnetic field response of the pipe at the i-th height. i |and the i-th height h i Based on the relationship between the two factors, estimate the depth d of the underground pipeline:

[0035] |ΔT i |=k(h i +d) α i = 1, 2, ..., M

[0036] Where k is a proportionality coefficient, representing the material properties and dimensional characteristics of the pipe; h i +d represents the vertical distance between the measurement node and the pipe, and α is the attenuation power, reflecting the rate of change of the total magnetic field of the pipe with respect to the vertical distance between the measurement point and the pipe. An empirical value of α = -2 is typically used to describe the attenuation characteristics of the magnetic field. Each node independently measures the total magnetic field response at its corresponding location, assuming that the measurements between different nodes do not interfere with each other. The scaling factor k and the pipe depth d are obtained through a nonlinear fitting method, i.e., minimizing the following objective function:

[0037]

[0038] The depth d of the underground pipeline is ultimately estimated by solving the problem using intelligent optimization algorithms (such as particle swarm optimization or PSO).

[0039] For the selected plurality of measurement nodes, the depth of the pipeline under each measurement node is obtained respectively, and then the depths obtained by the plurality of measurement nodes are averaged to obtain the final depth of the pipeline, so that the estimation accuracy can be improved through the plurality of measurement nodes; it is also applicable to the case of non-horizontal burying of the pipeline.

[0040] Another object of the present application is to provide a pipeline detection and positioning device for underground pipelines containing ferromagnetic materials.

[0041] The pipeline detection and positioning device for underground pipelines containing ferromagnetic materials comprises a rotating support, a motor and a computer, wherein the rotating support comprises a support frame, a rotating disc, a horizontal rod and measurement nodes; the rotating disc is arranged at the top end of the support frame, and the height of the support frame is adjustable; the center of the horizontal rod is arranged at the center of the rotating disc; a plurality of measurement nodes are arranged on the horizontal rod, and the distances from each measurement node to the center of the horizontal rod are different, forming an array of measurement nodes; each measurement node comprises a data acquisition module, a wireless communication module and a sensor module, the sensor module is connected to the data acquisition module, and the data acquisition module is connected to the wireless communication module; the sensor module comprises a fluxgate sensor and a position and attitude sensor; the rotating disc is connected to the motor; the measurement data of the measurement nodes is transmitted to the computer for processing through the wireless communication module.

[0042] The support frame adopts a support column or a tripod.

[0043] The measurement node of the present application adopts a low-cost integrated design: the fluxgate sensor, the position and attitude sensor and the wireless communication module of each measurement node are all low-cost, the fluxgate sensor is less than 10,000 yuan, and the other modules are several hundred yuan to several thousand yuan; compared with the use of a high-precision atomic magnetometer with a price of more than 200,000 yuan, the design cost of the present application is low, and the algorithm of the present application does not require high-precision data; the rotating measurement method is efficient: the traditional measurement method adopts line scanning / line scanning, which needs to linearly translate the measurement node array; for detecting the same area, the rotating scanning method is much more efficient, and can avoid the inconvenience of moving caused by uneven ground or mud; more importantly, rotating multiple times is equivalent to multiple measurements, if there is a pipeline, the data presents obvious periodicity, so it can be immediately judged whether there is a pipeline, without accurate data; if the data has no obvious periodicity, it indicates that it is environmental magnetic noise, i.e. no pipeline exists; the judgment and positioning method is simple: whether the pipeline exists can be immediately judged according to whether the data presents obvious periodicity, and the specific position and depth can be estimated by a simple optimization algorithm, the algorithm is stable and fast, can be processed in real time on site, and the precision can meet the needs of engineering application.

[0044] Advantages of the present application:

[0045] The application proposes a new type of rotating magnetic anomaly measurement method, which fixes multiple fluxgate sensors and position and attitude sensors on a non-magnetic aluminum support frame, rotates the measurement node array through driving, realizes rapid magnetic anomaly scanning measurement of the underground pipeline area, and quickly estimates the direction, horizontal position and depth of the pipeline. Its advantages include: (1) Compared with the traditional moving sensor point-by-point measurement method, this rotating scanning strategy greatly improves the efficiency and can avoid the problem of moving the sensor due to uneven ground or muddy inconvenience, especially suitable for detecting elongated ferromagnetic targets; (2) Using the coordinate information of the position of the magnetic field extreme point to estimate the direction and depth of the pipeline, without complex inversion algorithm and without relying on the assumption of uniform distribution of pipeline magnetic moment, it can estimate the position of the ferromagnetic target along any straight line with non-uniform distribution; Because the estimation method only uses the position of the magnetic field extreme point, it does not need accurate magnetic field values, so it is suitable for complex environments with strong interference, and the estimation time is short, supporting real-time positioning of the pipeline; (3) Using the extreme point position and size of the measurement data of each node at different heights, the depth of the pipeline under each node can be estimated, so even if the pipeline is not horizontally buried, it can also be applied. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 The target model diagram of an embodiment of the underground ferromagnetic material pipeline detection and positioning method of the application. DETAILED DESCRIPTION

[0047] The application will be further described below with reference to the accompanying drawings and specific embodiments.

[0048] The underground ferromagnetic material pipeline detection and positioning method of the embodiment includes the following steps:

[0049] 1) Pipeline detection and positioning device:

[0050] As Figure 1As shown, the rotating support includes a support frame, a rotating disc, a horizontal rod and measuring nodes; the support frame is a tripod, the rotating disc is arranged at the top of the tripod, and the height of the tripod is adjustable; the center of the horizontal rod is arranged at the center of the rotating disc; the materials of the tripod, the rotating disc and the horizontal rod are non-magnetic aluminum; first to fourth measuring nodes 1-4 are arranged on the horizontal rod, the length of the horizontal rod is 4 m, and the distances from the first to fourth measuring nodes to the center increase by 0.5 m successively, thereby forming a measuring node array; each measuring node includes a data acquisition module, a wireless communication module, a battery pack and a sensor module, the data acquisition module, the battery pack and the sensor module are placed in a non-magnetic box, the antenna of the wireless communication module is located outside the box, the overall size of the box is 30 cm*15 cm*10 cm, and the total weight is not greater than 1.5 kg, the sensor module is connected to the data acquisition module, the data acquisition module is connected to the wireless communication module, and the battery pack provides working voltage for the data acquisition module, the wireless communication module and the sensor module of the measuring node; the sensor module includes a fluxgate sensor and a position and attitude sensor, the position and attitude sensor adopts a GNSS / INS combined navigation chip, and the position and attitude of the measuring node, i.e., the longitude and latitude of the measuring node, the yaw angle, the pitch angle and the roll angle of the box are measured in real time; the fluxgate sensor is used to measure three components of the magnetic field;

[0051] The rotating disc is connected to the motor;

[0052] The measurement data of the measuring node is transmitted to the computer through the wireless communication module for processing; the real-time dynamic reference station is immovable, and it cooperates with the position and attitude sensor in all movable measuring nodes to improve the position measurement accuracy to the centimeter level; the position and attitude information is also collected by the data acquisition card and transmitted to the computer, and the computer uses the position and attitude information of each node to unify the measurement values of the fluxgate sensor in the body coordinate system of each node into the geographic coordinate system;

[0053] 2) Rotating magnetic field measurement:

[0054] A right-hand coordinate system is established, the X axis points to the north, the Y axis points to the east, and the Z axis points downward; let (x, y, z) represent the spatial coordinates of the measuring node, and (x0, y0, z0) represent the center point of the pipeline; the pipeline is buried at a depth d underground, the pipeline has a strike angle χ (relative to the geographic north, clockwise is positive), and the minimum horizontal distance between the rotation center and the pipeline is ρ; the motor drives the measuring node array on the horizontal rod to rotate around the vertical axis in the horizontal plane through the driving rotating disc, the measuring node array can perform 360° omnidirectional scanning on the detection area in the horizontal direction, and fast magnetic anomaly scanning measurement of the underground pipeline is realized;

[0055] 3) Estimation of the horizontal position and strike angle of the pipeline:

[0056] The motor drives the rotating disk to rotate the measuring node array on the horizontal rod in a horizontal plane at a fixed height. The measuring node array collects magnetic field and position information and transmits the information to the data acquisition module, which is transmitted to the computer through the wireless communication module. The computer extracts the position information of the measuring node when the magnetic field extreme point appears, and sets the position of the magnetic field extreme point as the candidate point of the suspicious pipeline.

[0057] The coordinates of all candidate points of the suspicious pipeline are V = {(x1, y1), (x2, y2), …, (x C ,y C )}, where (x j ,y j ) is the plane coordinates of the jth candidate point, and C is the number of candidate points. Assuming that there is only one underground pipeline, linear fitting is performed based on the least square method to find the best fitting straight line y = ax + b, where a is the slope and b is the intercept. The slope a and the intercept b are determined by the standard linear regression method under the condition of minimizing the sum of squared errors:

[0058]

[0059]

[0060] The final straight line is the pipeline trend angle and the pipeline center coordinates are

[0061] and the minimum horizontal distance from the rotation center to the pipeline The quality of linear fitting is evaluated by the determination coefficient R 2 , which is defined as follows:

[0062]

[0063] where y j represents the predicted y value of the fitting straight line, and y 2 is the average value of the observed values. The value of R i ranges from 0 to 1, and the closer the value is to 1, the better the fitting effect.

[0064] 4) Estimation of pipeline depth:

[0065] Adjust the height of the rotating support and drive the measuring node array to rotate at different heights from the ground to measure. For underground pipelines with a depth of about 3m, the height interval is 30cm, and the deeper the pipeline, the larger the interval, such as

[0066] ​h1=50cm, h2=80cm, h3=1.1m, M=3, h1~h3 are the first to third heights; select one measurement node, at each height, obtain the total magnetic field response of the selected measurement node respectively; total magnetic field response ΔT i The difference between the total magnetic field extreme value at the ith height and the background geomagnetic field is defined as absolute value:

[0067]

[0068] Wherein, The total magnetic field extreme value recorded by the measurement node at the ith height, in actual operation, the magnetic field extreme value of each circle is usually extracted after rotating multiple circles and averaged to obtain the total magnetic field extreme value to obtain a stable estimate, the position of the total magnetic field extreme value at different heights is the same, but the total magnetic field extreme value is different; T geo The background total magnetic field value output by the measurement node, usually taking the average value of the total field measured by the node in the area without the influence of the pipeline. By analyzing the absolute value of the pipeline total magnetic field response |ΔT i | at the ith height h i , the depth d of the underground pipeline is estimated:

[0069] |ΔT i | = k (h i +d) α , i = 1, 2, …, M

[0070] Wherein, k is the proportional coefficient, which represents the material properties and size characteristics of the pipeline; h i +d represents the vertical distance between the measurement node and the pipeline, and α reflects the speed of the total magnetic field of the pipeline with the vertical distance between the measurement point and the pipeline, usually taking the experience value α =-2 to describe the attenuation characteristics of the magnetic field. Each node independently measures the total magnetic field response at the corresponding position, assuming that the measurement values of different measurement nodes do not interfere with each other; the proportional coefficient k and the depth d of the pipeline are obtained by a nonlinear fitting method, that is, the following objective function is minimized:

[0071]

[0072] Solve by intelligent optimization algorithm (such as particle swarm optimization or PSO), so as to finally estimate the depth d of the underground pipeline; for the selected multiple measurement nodes, the depth of the pipeline below each measurement node is obtained respectively, and then the average value of the depths obtained by the multiple measurement nodes is taken to obtain the final depth of the pipeline, so that the estimation accuracy can be improved by multiple measurement nodes; it is also applicable to the case of non-horizontal laying of the pipeline.

[0073] Finally, it is to be understood that the embodiments are for purposes of illustration only and that various changes and modifications can be made by those skilled in the art without departing from the scope of the application as disclosed in the specification and appended claims. Therefore, the scope of the application is not to be limited to the embodiments disclosed but is to be accorded the full scope permissible by the appended claims.

Claims

1. A method for detecting and locating underground pipelines containing ferromagnetic materials, characterized in that, The method includes the following steps: 1) Pipeline detection and positioning device: One or more measurement nodes constitute a measurement node array; 2) Rotating magnetic field measurement: A right-handed coordinate system is established, and the measurement node array is driven to rotate in the horizontal plane. The measurement node array can perform a 360° all-round scan of the detection area in the horizontal direction, realizing rapid magnetic anomaly scanning measurement of underground pipelines. 3) Estimation of the horizontal position and orientation angle of the pipeline: The driving measurement node array rotates on a horizontal plane at a fixed height, and the magnetic field, position and attitude information of the measurement nodes are transmitted to the computer; the computer extracts the position information of the measurement nodes when the magnetic field extreme point appears, and the position of the magnetic field extreme point is set as a candidate point for the existence of a suspicious pipe; then all the candidate points for the existence of a suspicious pipe are fitted into a straight line to obtain the horizontal position and direction angle of the pipe; 4) Pipe depth estimation: Adjust the height of the measurement node array and perform rotational measurements at multiple heights above the ground. Select one or more measurement nodes and obtain the total magnetic field response of the pipeline at each selected measurement node at each height. Then, estimate the depth of the underground pipeline by analyzing the relationship between the total magnetic field response of the pipeline at each height and the corresponding height.

2. The method as described in claim 1, characterized in that, The real-time position and attitude information of each measurement node is obtained by position and attitude sensors, and the magnetic field is obtained by fluxgate sensors. The data acquisition module collects this information and transmits it to the computer. The computer uses this position and attitude information to unify the measurement values ​​of the fluxgate sensors in each measurement node in the measurement node body coordinate system to the geographic coordinate system. The stationary real-time dynamic measurement reference station works in conjunction with the position and attitude sensors in all movable measurement nodes to improve the position measurement accuracy to the centimeter level.

3. The method as described in claim 1, characterized in that, The coordinates of all candidate points for the suspected pipelines are V = {(x1,y1),(x2,y2),…,(x...} C ,y C )}, where (x j ,y j Let be the planar coordinates of the j-th candidate point, j = 1, ..., C, where C is the number of candidate points; linear fitting is performed based on the least squares method to find the best-fitting line y = ax + b, where a is the slope and b is the intercept. The slope a and intercept b are determined by standard linear regression under the condition of minimizing the sum of squared errors. The resulting straight line represents the pipe's direction angle. The center coordinates of the pipeline are and the minimum horizontal distance from the center of rotation to the pipe Where x0 and y0 represent the planar coordinates of the center point of the pipe.

4. The method as described in claim 1, characterized in that, In step 4), the total magnetic field response of the pipeline is ΔT i Defined as the absolute value of the difference between the total magnetic field extremum at the i-th altitude and the background geomagnetic field: in, T represents the extreme value of the total magnetic field recorded at the i-th height by the measuring node. geo The background total magnetic field value output by this measurement node; by analyzing the absolute value of the total magnetic field response of the pipeline at the i-th height |ΔT i |and the i-th height h i Based on the relationship between the two factors, estimate the depth d of the underground pipeline: |ΔT i |=k(h i +d) α ,i=1,2,…,M Where k is the scaling factor and α is the attenuation power; the scaling factor k and the pipe depth d are obtained through a nonlinear fitting method, i.e., minimizing the following objective function: The depth d of the underground pipeline is estimated by solving the problem using an intelligent optimization algorithm.

5. The method as described in claim 1, characterized in that, For a selection of multiple measurement nodes, the depth of the pipe below each node is obtained. Then, the average of the depths obtained from the multiple measurement nodes is taken to obtain the final pipe depth.

6. A device for detecting and locating underground pipelines containing ferromagnetic materials, characterized in that, The underground ferromagnetic pipeline detection and positioning device includes: a rotating support, a motor, and a computer; wherein, the rotating support includes a support frame, a rotating disk, a horizontal bar, and measuring nodes; the rotating disk is set at the top of the support frame, and the height of the support frame is adjustable; the center of the horizontal bar is set at the center of the rotating disk; one or more measuring nodes are set on the horizontal bar, and the distance from each measuring node to the center of the horizontal bar is different, forming a measuring node array; each measuring node includes a data acquisition module, a wireless communication module, and a sensor module, the sensor module being connected to the data acquisition module, and the data acquisition module being connected to the wireless communication module; the sensor module includes a fluxgate sensor and a position and attitude sensor; the rotating disk is connected to the motor; the measurement data of the measuring nodes is transmitted to the computer for processing through the wireless communication module.

7. The pipeline detection and positioning device as described in claim 6, characterized in that, The support frame, rotating disk, and horizontal bar are made of non-magnetic materials.

8. The pipeline detection and positioning device as described in claim 6, characterized in that, The measurement node also includes a battery pack, which provides operating voltage for the measurement node's data acquisition module, wireless communication module, and sensor module.

9. The pipeline detection and positioning device as described in claim 6, characterized in that, It also includes a real-time dynamic measurement reference station, which is stationary. The real-time dynamic measurement reference station works in conjunction with the position and attitude sensors in all movable measurement nodes to improve the accuracy of position measurement.

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