Dual-node magnetic field compensation method and system based on semi-airborne electromagnetic detection

Abstract

This invention provides a dual-node magnetic field compensation method and system based on semi-airborne electromagnetic detection. During flight, front-end and rear-end magnetic field sensing units are deployed at intervals along the flight direction. For the same spatial location, the front-end unit collects magnetic field data first, followed by the rear-end unit, and records time, position, and attitude information. The magnetic field data collected before and after are spatiotemporally matched to establish a correspondence between the two sets of data at the same spatial location. After coordinate unification and attitude correction, the corresponding magnetic field data are compensated to reduce common interference components and retain the differential response caused by changes in the underground medium. This invention utilizes the revisit relationship formed by the front-end and rear-end deployment, which helps to reduce common interference from the platform and improve the quality of magnetic field data and anomaly detection capabilities.

Description

Technical Field

[0001] This invention belongs to the field of semi-airborne electromagnetic detection and electromagnetic data processing technology, and in particular relates to a two-node magnetic field compensation method and system based on semi-airborne electromagnetic detection. Background Technology

[0002] Semi-airborne electromagnetic detection (SEM) is an important technology that utilizes electromagnetic sensors mounted on airborne platforms to acquire the electrical response of underground media. It features a large detection range, high operational efficiency, and strong adaptability to complex terrain, making it valuable for applications in resource exploration, engineering geological surveys, and disaster identification. For passive-source airborne electromagnetic detection and semi-airborne electromagnetic detection with the excitation source fixed to the ground, existing receiving methods typically employ a single triaxial magnetic field sensor or a single set of orthogonal magnetic field sensors. While this method can achieve magnetic field vector measurement, during the dynamic flight of the airborne platform, the received data is easily affected by factors such as primary field residue, slow changes in the geomagnetic background, platform attitude changes, electromagnetic interference from the aircraft, and vibration noise. These interferences superimpose with the underground target response, and some interferences have obvious common component characteristics, easily masking effective anomaly information and affecting data consistency, repeatability, and detection accuracy. Existing technologies mostly use post-processing methods such as filtering, smoothing, baseline correction, and attitude correction, but there is still a lack of effective direct suppression methods for common interference components, and the noise reduction process can easily weaken the true anomaly response.

[0003] Therefore, it is necessary to propose a new semi-airborne electromagnetic receiving and data compensation technology to improve the signal-to-noise ratio, stability, and anomaly resolution of semi-airborne electromagnetic detection data. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a two-node magnetic field compensation method and system based on semi-airborne electromagnetic detection.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] On the one hand, a two-node magnetic field compensation method based on semi-airborne electromagnetic detection is provided, including the following steps: During the flight of the aviation platform, the front-end magnetic field sensing unit and the rear-end magnetic field sensing unit are arranged at intervals along the flight direction. For the same spatial position, the front-end magnetic field sensing unit collects the front magnetic field data of the same spatial position at a earlier time, and the rear-end magnetic field sensing unit collects the rear magnetic field data of the same spatial position at a later time. The time, spatial position and attitude information of each sampling point are recorded respectively. Based on the preset spacing, flight speed, sampling time difference, track position and spatial coordinate information between the front magnetic field sensing unit and the back magnetic field sensing unit, the front magnetic field data and the back magnetic field data are spatiotemporally matched to establish the correspondence between the data collected by the back magnetic field sensing unit at a later time and the data of the same spatial position collected by the front magnetic field sensing unit at an earlier time, thus forming a pair of corresponding front and back magnetic field data. Based on the attitude information, coordinate unification and attitude correction are performed on the corresponding magnetic field data pairs before and after; Compensation processing is performed on the corresponding magnetic field data pairs before and after coordinate unification and attitude correction to weaken common interference components and retain the differential response caused by changes in the underground medium space, thereby obtaining compensated magnetic field data or anomalous enhancement data.

[0007] Furthermore, the spatiotemporal matching method employs one or more of the following: The theoretical time delay is calculated based on the preset distance between the front-end magnetic field sensing unit and the back-end magnetic field sensing unit and the flight speed, and the corresponding sampling point is determined accordingly to complete the spatiotemporal matching. Spatiotemporal matching is performed based on the principle of closest spatial coordinate information between sampling points; Spatiotemporal matching is performed based on the cumulative length of the flight path or the location of the trajectory. Spatiotemporal matching is performed by combining sampling time, spatial coordinate information, and track position information.

[0008] Furthermore, if both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use triaxial magnetic field sensors, the coordinate transformation of the front magnetic field data and the back magnetic field data in the corresponding sampling time of the front and back magnetic field data pairs is performed based on the attitude parameters of the corresponding sampling time of the front and back magnetic field data pairs, and unified to the same reference coordinate system.

[0009] Furthermore, the three-axis magnetic field vectors collected by the front-end magnetic field sensing unit and the three-axis magnetic field vectors collected by the rear-end magnetic field sensing unit in the corresponding magnetic field data pairs after coordinate unification and attitude correction are respectively processed by differential, weighted differential or vector compensation.

[0010] Furthermore, if both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use two-dimensional or one-dimensional magnetic field sensors, the magnetic field components in the corresponding directions can be corrected or converted for consistency based on the measurement direction and attitude change relationship of the front magnetic field data and the back magnetic field data in the corresponding magnetic field data pairs.

[0011] Furthermore, the magnetic field components in the corresponding directions of the front two-dimensional or one-dimensional magnetic field components and the back two-dimensional or one-dimensional magnetic field components in the corresponding magnetic field data pairs after coordinate unification and attitude correction are subjected to differential, weighted compensation, or common component weakening processing to obtain the compensated magnetic field components in the corresponding directions.

[0012] On the other hand, a two-node magnetic field compensation system based on semi-airborne electromagnetic detection is provided to implement the above-mentioned two-node magnetic field compensation method based on semi-airborne electromagnetic detection, including: The front-end magnetic field sensing unit is used to continuously acquire magnetic field response data of the front-end position during flight; The rear magnetic field sensing unit is used to continuously acquire magnetic field response data of the rear position during flight; The mounting connection structure is used to maintain the relative positional relationship between the front-end magnetic field sensing unit and the rear-end magnetic field sensing unit; Auxiliary unit, used to acquire flight position and attitude information of the aviation platform; The data unit is used to complete data acquisition, coordinate unification and attitude correction, and compensation processing. Both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit are mounted on an aviation platform and are arranged at intervals along the flight direction of the aviation platform, maintaining a preset distance between them. This allows the back-end magnetic field sensing unit to pass through or near the position previously measured by the front-end magnetic field sensing unit during flight, forming a revisit relationship between the back-end magnetic field sensing unit and the front-end magnetic field sensing unit. The data unit is configured to record magnetic field data collected by the front-end sensing unit at an earlier time and magnetic field data collected by the back-end sensing unit at a later time at the same spatial location, and to establish a correspondence between the two.

[0013] The front-end magnetic field sensing unit and the back-end magnetic field sensing unit described in this invention are both triaxial magnetic field sensors, two-dimensional magnetic field sensors, or one-dimensional magnetic field sensors.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a dual-node magnetic field compensation method and system based on semi-airborne electromagnetic detection, applicable to passive source airborne electromagnetic detection and semi-airborne electromagnetic detection scenarios where the excitation source is fixed on the ground. During the flight of the airborne platform, front-end and rear-end magnetic field sensing units are deployed at intervals along the flight direction. For the same spatial location, the front-end collects magnetic field data first, followed by the rear-end, and records time, position, and attitude information. The magnetic field data collected before and after are spatiotemporally matched to establish a correspondence between the magnetic field data collected before and after at the same spatial location. After coordinate unification and attitude correction, the corresponding magnetic field data before and after are compensated to weaken common interference components and retain the differential response caused by changes in the underground medium. This invention utilizes the revisit relationship formed by the front-and-back deployment to effectively suppress platform interference and improve the accuracy of magnetic field detection.

[0015] The core of this invention lies not in simply adding a magnetic field sensor, but in constructing a dual-node magnetic field observation configuration with rigid intervals along the flight direction. This allows the rear-end magnetic field sensing unit to pass through positions previously observed or near by the front-end magnetic field sensing unit after a certain time delay during continuous flight, thus establishing a revisit relationship between the rear-end observation and the historical measurement points of the front-end. Based on this revisit relationship, a temporal, spatial, and trajectory correspondence can be established between the front and rear observation data. Combined with attitude information and coordinate processing, this enables compensation and reduction of common interference components. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart of a two-node magnetic field compensation method based on semi-airborne electromagnetic detection provided in one embodiment; Figure 2 This is a schematic diagram of one embodiment where both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use triaxial magnetic field sensors. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described through specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Reference Figure 1 One embodiment provides a two-node magnetic field compensation method based on semi-airborne electromagnetic detection, including the following steps: During the flight of the aviation platform, the front-end magnetic field sensing unit and the rear-end magnetic field sensing unit are arranged at intervals along the flight direction. For the same spatial position, the front-end magnetic field sensing unit collects the front magnetic field data of the same spatial position at a earlier time, and the rear-end magnetic field sensing unit collects the rear magnetic field data of the same spatial position at a later time. The time, spatial position and attitude information of each sampling point are recorded respectively. Based on the preset spacing, flight speed, sampling time difference, track position and spatial coordinate information between the front magnetic field sensing unit and the back magnetic field sensing unit, the front magnetic field data and the back magnetic field data are spatiotemporally matched to establish the correspondence between the data collected by the back magnetic field sensing unit at a later time and the data of the same spatial position collected by the front magnetic field sensing unit at an earlier time, thus forming a pair of corresponding front and back magnetic field data. Based on the attitude information, coordinate unification and attitude correction are performed on the corresponding magnetic field data pairs before and after; Compensation processing is performed on the corresponding magnetic field data pairs before and after coordinate unification and attitude correction to weaken common interference components and retain the differential response caused by changes in the underground medium space, thereby obtaining compensated magnetic field data or anomalous enhancement data.

[0020] In the above embodiments, when the front-end magnetic field sensing unit and the back-end magnetic field sensing unit collect magnetic field data, each sampling point records the sampling time, spatial position, and attitude information, and records them under a unified time reference to ensure the accuracy of subsequent data matching. The front-end and back-end magnetic field sensing units can both be triaxial magnetic field sensors, two-dimensional magnetic field sensors, or one-dimensional magnetic field sensors. Specifically, when both the front-end and back-end magnetic field sensing units use triaxial magnetic field sensors, the collected magnetic field data consists of magnetic field components in three orthogonal directions; when both the front-end and back-end magnetic field sensing units use two-dimensional or one-dimensional magnetic field sensors, the collected magnetic field data consists of magnetic field components in the corresponding directions.

[0021] Based on the preset spacing, flight speed, sampling time difference, track position, and spatial coordinate information between the front-end and back-end magnetic field sensing units, spatiotemporal matching is performed on the front and back magnetic field data. The goal is to establish a correspondence between the current observation data collected by the back-end magnetic field sensing unit at the same spatial location and the magnetic field data collected by the front-end magnetic field sensing unit at an earlier time at the same spatial location (understandably, "the same spatial location" refers to a similar spatial location within a preset deviation range, not a completely ideal situation in reality). This forms corresponding front-to-back magnetic field data pairs, providing a foundation for subsequent compensation processing. Regarding the spatiotemporal matching method, those skilled in the art can use existing spatiotemporal matching methods to achieve spatiotemporal matching of the front and back magnetic field data corresponding to the front and back magnetic field sensing units. This invention does not impose specific limitations on the choice of spatiotemporal matching method; the spatiotemporal matching method is not limited and can employ one or more of the following: The theoretical time delay is calculated based on the preset distance between the front-end magnetic field sensing unit and the back-end magnetic field sensing unit and the flight speed, and the corresponding sampling point is determined accordingly to complete the spatiotemporal matching. Spatiotemporal matching is performed based on the principle of closest spatial coordinate information between sampling points; Spatiotemporal matching is performed based on the cumulative length of the flight path or the location of the trajectory. Spatiotemporal matching is performed by combining sampling time, spatial coordinate information, and track position information.

[0022] The spatiotemporal matching method, which calculates the theoretical time delay based on the preset distance and flight speed between the front-end magnetic field sensing unit and the back-end magnetic field sensing unit, first calculates the theoretical delay time based on the installation distance and local flight speed between the front-end magnetic field sensing unit and the back-end magnetic field sensing unit. Then, with this theoretical time as the center, it searches for candidate sampling points of another sensing unit within a preset time window and confirms the final matching point by combining the spatial position deviation.

[0023] The spatiotemporal matching method based on the principle of closest spatial coordinate information of front and rear sampling points can first take the current sampling point of the front-end magnetic field sensing unit as the benchmark, calculate the spatial distance of each sampling point within the reasonable historical search range of the back-end magnetic field sensing unit, and select the sampling point with the smallest spatial distance and that meets the preset spatial threshold as the final matching point.

[0024] Based on the spatiotemporal matching method of cumulative track length or trajectory position, the flight track can be reconstructed first based on the positioning data, and the cumulative track length or trajectory position parameters corresponding to each sampling point can be calculated. Then, the sampling point with the closest track position in another sensing unit can be searched, and the consistency can be checked by combining spatial coordinates and time relationship to confirm the final matching point.

[0025] Based on the joint spatiotemporal matching method of sampling time, spatial coordinate information and track position information, a coarse screening can be performed first based on the theoretical time delay range. Then, the time deviation, spatial distance difference and track position difference of the candidate points can be calculated, and a comprehensive error index can be constructed according to the preset weights. The sampling point with the smallest comprehensive error and that meets the threshold can be selected as the final matching point.

[0026] Since the attitude of the aircraft platform may change when the front-end magnetic field sensing unit and the back-end magnetic field sensing unit sample the same spatial position at different times, the magnetic field data measured before and after need to be corrected for attitude.

[0027] If both the front-end and back-end magnetic field sensing units use triaxial magnetic field sensors, based on the attitude parameters of the corresponding sampling times for the front and back magnetic field data pairs, coordinate transformation is performed on the front and back magnetic field data in the corresponding magnetic field data pairs to unify them to the same reference coordinate system. Specific steps include: The attitude parameters corresponding to the front-end sampling time and the back-end sampling time are obtained respectively. The attitude parameters include roll angle, pitch angle and yaw angle. The attitude parameters can be provided by inertial measurement unit, attitude and heading reference system or navigation system. A reference coordinate system is preset for unified comparison of the front and back magnetic field data, such as the geographic coordinate system.

[0028] Based on the attitude parameters corresponding to the front-end sampling time, a coordinate transformation relationship is established from the instantaneous carrier coordinate system where the front-end magnetic field sensing unit is located to the reference coordinate system. Based on the attitude parameters corresponding to the back-end sampling time, a coordinate transformation relationship is established from the instantaneous carrier coordinate system where the back-end magnetic field sensing unit is located to the reference coordinate system.

[0029] By utilizing coordinate transformation relationships, the front and rear magnetic field data are converted to the reference coordinate system to obtain the attitude-corrected three-axis magnetic field data.

[0030] If both the front-end and back-end magnetic field sensing units use two-dimensional or one-dimensional magnetic field sensors, the direction correction or consistency conversion of the magnetic field components in the corresponding directions can be performed based on the measurement direction and attitude change relationship of the front and back magnetic field data in the corresponding magnetic field data pairs. The principle is similar to that of a three-axis magnetic field sensor. The difference is that a three-axis magnetic field sensor processes the entire set of three-axis vectors, while a two-dimensional or one-dimensional magnetic field sensor mainly processes one or two magnetic field components in the corresponding direction.

[0031] After completing the above steps, the two sets of data are comparable. Next, compensation processing is performed on the corresponding magnetic field data to identify and reduce common interference components in the observations, while preserving the differences caused by variations in the underground medium. These common interference components may include primary field residue, slow background drift, platform attitude coupling effects, electromagnetic interference from the machine body, and other common disturbances.

[0032] When both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use triaxial magnetic field sensors, the front triaxial magnetic field vector and the back triaxial magnetic field vector in the corresponding front and rear magnetic field data pairs after coordinate unification and attitude correction are respectively processed by differential, weighted differential or vector compensation.

[0033] Differential method: When the common interference components of the data obtained by the two magnetic sensors at the front and back ends are approximately the same, this method can be used. Directly subtract the corresponding three components of the three-axis magnetic field vector of the back end from the three components of the front-end three-axis magnetic field vector to obtain the compensation results in three directions, and combine the compensation results in these three directions to form the compensated three-axis magnetic field vector.

[0034] Weighted Differential: When the amplitudes of common interference components in the back-end and front-end observation data are not completely equal but have a strong correlation, a weighted differential method can be used. The compensation weight coefficient is determined based on the background segment data, calibration data, or preset rules. This weight coefficient is then used to scale the latter three-axis magnetic field vector, and finally, a differential calculation is performed between the latter and former three-axis magnetic field vectors in the corresponding directions to obtain the compensation result.

[0035] Vector compensation: When it is necessary to preserve the overall vector relationship of the magnetic field rather than just performing component-by-component differentiation, vector compensation can be used. The first three-axis magnetic field vector and the second three-axis magnetic field vector are treated as two three-dimensional vectors as a whole. The common vector components are weakened according to the preset compensation rules, while the differential vector components reflecting the spatial changes of the underground medium are retained. Finally, the compensated three-dimensional magnetic field vector is output.

[0036] The compensation weight coefficients involved can be fixed values ​​or determined based on the correlation, amplitude ratio, or minimum residual criterion of the preceding and following observation data within the background stable section.

[0037] When both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use two-dimensional or one-dimensional magnetic field sensors, the magnetic field components in the corresponding directions of the front two-dimensional or one-dimensional magnetic field components and the back two-dimensional or one-dimensional magnetic field components in the corresponding magnetic field data pairs after attitude correction are directly differentiated, weighted compensated, or have common component weakening processed to obtain the compensated magnetic field components in the corresponding directions.

[0038] Direct difference: Subtract the magnetic field components in the corresponding directions from the corresponding magnetic field data before and after to obtain the compensation result in that direction.

[0039] Weighted compensation: First, multiply the magnetic field component in the corresponding direction of the back end by a weighting coefficient, and then subtract it from the magnetic field component in the corresponding direction of the front end to obtain the compensation result.

[0040] Common component attenuation processing: Based on the correlation between the corresponding directional components of the corresponding magnetic field data before and after, the background interference or platform interference that exists in both is attenuated, while the variable part is retained.

[0041] In the above embodiments, specific compensation methods may include direct difference, weighted difference, sliding window compensation, common component attenuation based on correlation, and common component separation based on background estimation. Through the above compensation processing, compensated magnetic field data or anomalous enhancement data can be obtained.

[0042] Furthermore, when both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use triaxial magnetic field sensors, the compensation process can be further limited to the following preferred form: Assume that the coordinates corresponding to the current spatial position are aligned with the corresponding magnetic field data before and after attitude correction, including... The front-end magnetic field sensing unit collects the first three axes magnetic field vectors. , The three-axis magnetic field vector acquired by the back-end magnetic field sensing unit at any moment The compensated three-axis magnetic field vector at the current spatial position for:

[0043] in, To compensate for the weighting coefficients, the front-end magnetic field sensing unit measures the current spatial location at the same location. The first three axes magnetic field vectors collected at different times The back-end magnetic field sensing unit detects the current spatial location at the same location. The three-axis magnetic field vectors acquired at each moment Furthermore, Take a constant of 1 or obtain it according to the minimum variance criterion of the background segment, the least squares estimation criterion, or the correlation constraint criterion.

[0044] The above processing can weaken the common interference components with strong correlation between the previous and subsequent observations, while preserving or enhancing the differential response caused by the spatial changes in the underground medium in the compensation results.

[0045] In another embodiment, a two-node magnetic field compensation system based on semi-airborne electromagnetic detection is provided to implement the two-node magnetic field compensation method based on semi-airborne electromagnetic detection described in any of the above embodiments, comprising: The front-end magnetic field sensing unit is used to continuously acquire magnetic field response data of the front-end position during flight; The rear magnetic field sensing unit is used to continuously acquire magnetic field response data of the rear position during flight; The mounting connection structure is used to maintain the relative positional relationship between the front-end magnetic field sensing unit and the rear-end magnetic field sensing unit; Auxiliary unit, used to acquire flight position and attitude information of the aviation platform; The data unit is used to complete the data acquisition, coordinate unification and attitude correction, and compensation processing steps in the dual-node magnetic field compensation method based on semi-airborne electromagnetic detection. Both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit are mounted on an aviation platform and are arranged at intervals along the flight direction of the aviation platform, maintaining a preset distance between them. This allows the back-end magnetic field sensing unit to pass through or near the position previously measured by the front-end magnetic field sensing unit during flight, forming a revisit relationship between the back-end magnetic field sensing unit and the front-end magnetic field sensing unit. The data unit is configured to record magnetic field data collected by the front-end sensing unit at an earlier time and magnetic field data collected by the back-end sensing unit at a later time at the same spatial location, and to establish a correspondence between the two.

[0046] Similarly, both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit are triaxial magnetic field sensors, two-dimensional magnetic field sensors, or one-dimensional magnetic field sensors. For example... Figure 2 The diagram illustrates an embodiment where both the front-end and rear-end magnetic field sensing units utilize triaxial magnetic field sensors. The front-end magnetic field sensing unit is triaxial magnetic sensor A, and the rear-end magnetic field sensing unit is triaxial magnetic sensor B, connected by a non-magnetic rigid link structure. The triaxial magnetic field sensor includes an X-axis coil, a Y-axis coil, and a Z-axis coil. It measures the magnetic field components in three orthogonal directions at its location and outputs three-dimensional magnetic field vector data. The magnetic field sensing unit can also be a two-dimensional or one-dimensional magnetic field sensor to acquire magnetic field component data in the corresponding directions. The front-end and rear-end magnetic field sensing units are arranged at intervals along the flight direction of the aircraft platform, with the front end located in front of the flight direction and the rear end in the rear. A preset distance is maintained between the two sensing units, which can be set according to flight speed, sampling frequency, platform size, and detection requirements. A relatively fixed or calibrable spatial relationship (1m~5m) is maintained between the two sensing units to ensure that subsequent front-end and rear-end data can be matched accordingly. By adopting a front-and-rear deployment method, during continuous flight, the rear-end magnetic field sensing unit will pass through the location previously measured by the front-end magnetic field sensing unit or a similar location after a certain time delay, thus forming a revisit relationship between the rear-end observation and the historical measurement points of the front-end. This revisit relationship is the key basis that distinguishes this scheme from the single-sensor airborne electromagnetic reception method. Its significance lies not in simply adding a sensor, but in using the flight motion process to establish a spatial correspondence between two measurements, providing conditions for subsequent data matching and compensation processing.

[0047] In summary, the present invention employs a receiving structure in which the front-end magnetic field sensing unit and the rear-end magnetic field sensing unit are arranged at intervals along the flight direction. This structure enables the formation of a continuous observation relationship between adjacent spatial positions during the continuous flight of the aircraft platform, providing a direct data basis for the matching analysis and compensation processing of magnetic field data at corresponding positions.

[0048] This invention utilizes the revisit capability of the back-end magnetic field sensing unit to the historical measurement positions of the front-end magnetic field sensing unit to perform spatiotemporal matching and compensation processing on the front and back magnetic field vector data. This helps to identify and reduce common interference components such as primary field residue, slow background drift, platform attitude coupling, and electromagnetic interference from the machine body, thereby improving the targeting and effectiveness of data processing.

[0049] This invention combines sensor spatial configuration with magnetic field data compensation process, which reduces common interference components while retaining spatial difference information corresponding to underground medium anomalies, thereby improving the consistency, stability and anomaly resolution of airborne electromagnetic data.

[0050] Preferably, both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit adopt triaxial magnetic field sensors. By performing unified matching and compensation processing on the triaxial magnetic field vector data, the coupling relationship between magnetic field components in different directions can be taken into account, providing relatively complete data support for subsequent anomaly identification, profile interpretation and imaging processing.

[0051] This invention eliminates the need for an additional independent reference observation unit and utilizes the trajectory overlap relationship between the front and rear sensors to achieve self-reference compensation, which helps simplify system configuration and operation process and improves the convenience of engineering implementation.

[0052] This invention is applicable to both three-axis magnetic field vector compensation and corresponding compensation processing of two-dimensional or one-dimensional magnetic field components, and can be adapted to different forms of magnetic field observation.

[0053] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-node magnetic field compensation method based on semi-airborne electromagnetic detection, characterized in that, Includes the following steps: During the flight of the aviation platform, the front-end magnetic field sensing unit and the rear-end magnetic field sensing unit are arranged at intervals along the flight direction. For the same spatial position, the front-end magnetic field sensing unit collects the front magnetic field data of the same spatial position at a earlier time, and the rear-end magnetic field sensing unit collects the rear magnetic field data of the same spatial position at a later time. The time, spatial position and attitude information of each sampling point are recorded respectively. Based on the preset spacing, flight speed, sampling time difference, track position and spatial coordinate information between the front magnetic field sensing unit and the back magnetic field sensing unit, the front magnetic field data and the back magnetic field data are spatiotemporally matched to establish the correspondence between the data collected by the back magnetic field sensing unit at a later time and the data of the same spatial position collected by the front magnetic field sensing unit at an earlier time, thus forming a pair of corresponding front and back magnetic field data. Based on the attitude information, coordinate unification and attitude correction are performed on the corresponding magnetic field data pairs before and after. Both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use triaxial magnetic field sensors. Based on the attitude parameters of the corresponding sampling time of the corresponding magnetic field data pairs before and after, coordinate transformation is performed on the front magnetic field data and the back magnetic field data in the corresponding magnetic field data pairs before and after, unifying them to the same reference coordinate system. Alternatively, both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use two-dimensional or one-dimensional magnetic field sensors. Based on the measurement direction and attitude change relationship of the front magnetic field data and the back magnetic field data in the corresponding magnetic field data pairs before and after, direction correction or consistency conversion is performed on the magnetic field components in the corresponding directions. Compensation processing is performed on the corresponding magnetic field data pairs before and after coordinate unification and attitude correction to weaken common interference components and retain the differential response caused by changes in the underground medium space, thereby obtaining compensated magnetic field data or anomalous enhancement data. When both the front-end and back-end magnetic field sensing units use triaxial magnetic field sensors, the compensation processing includes: performing differential, weighted differential, or vector compensation processing on the triaxial magnetic field vectors collected by the front-end and back-end magnetic field sensing units in the corresponding magnetic field data pairs after coordinate unification and attitude correction; or, the compensation processing includes: assuming that the corresponding magnetic field data pairs before and after coordinate unification and attitude correction corresponding to the current spatial position include... The front-end magnetic field sensing unit collects the first three axes magnetic field vectors. , The three-axis magnetic field vector acquired by the back-end magnetic field sensing unit at any moment The compensated three-axis magnetic field vector at the current spatial position for: in, To compensate for the weighting coefficient, Take a constant of 1 or obtain it based on the minimum variance criterion of the background segment, the least squares estimation criterion, or the correlation constraint criterion; Alternatively, when both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit use two-dimensional or one-dimensional magnetic field sensors, the compensation process includes: performing differential, weighted compensation, or common component weakening processing on the magnetic field components in the corresponding directions of the front two-dimensional or one-dimensional magnetic field components and the back two-dimensional or one-dimensional magnetic field components in the corresponding magnetic field data pairs after coordinate unification and attitude correction, to obtain the compensated magnetic field components in the corresponding directions.

2. The dual-node magnetic field compensation method based on semi-airborne electromagnetic detection according to claim 1, characterized in that, The spatiotemporal matching method employs one or more of the following: The theoretical time delay is calculated based on the preset distance between the front-end magnetic field sensing unit and the back-end magnetic field sensing unit and the flight speed, and the corresponding sampling point is determined accordingly to complete the spatiotemporal matching. Spatiotemporal matching is performed based on the principle of closest spatial coordinate information between sampling points; Spatiotemporal matching is performed based on the cumulative length of the flight path or the location of the trajectory. Spatiotemporal matching is performed by combining sampling time, spatial coordinate information, and track position information.

3. A two-node magnetic field compensation system based on semi-airborne electromagnetic detection, used to implement the two-node magnetic field compensation method based on semi-airborne electromagnetic detection as described in claim 1, characterized in that, include: The front-end magnetic field sensing unit is used to continuously acquire magnetic field response data of the front-end position during flight; The rear magnetic field sensing unit is used to continuously acquire magnetic field response data of the rear position during flight; The mounting connection structure is used to maintain the relative positional relationship between the front-end magnetic field sensing unit and the rear-end magnetic field sensing unit; Auxiliary unit, used to acquire flight position and attitude information of the aviation platform; The data unit is used to complete data acquisition, coordinate unification and attitude correction, and compensation processing. Both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit are mounted on an aviation platform and are arranged at intervals along the flight direction of the aviation platform, maintaining a preset distance between them. This allows the back-end magnetic field sensing unit to pass through or near the position previously measured by the front-end magnetic field sensing unit during flight, forming a revisit relationship between the back-end magnetic field sensing unit and the front-end magnetic field sensing unit. The data unit is configured to record magnetic field data collected by the front-end sensing unit at an earlier time and magnetic field data collected by the back-end sensing unit at a later time at the same spatial location, and to establish a correspondence between the two.

4. The dual-node magnetic field compensation system based on semi-airborne electromagnetic detection according to claim 3, characterized in that, Both the front-end magnetic field sensing unit and the back-end magnetic field sensing unit are triaxial magnetic field sensors, two-dimensional magnetic field sensors, or one-dimensional magnetic field sensors.

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