A method for topographic correction of magnetic anomalies using topographic surface magnetic charge distribution.

Abstract

This invention provides a method for topographic correction of magnetic anomalies using topographic surface magnetic charge distribution, comprising: Step 1. Data acquisition and preprocessing; Step 2. Construction of a topographic surface magnetic charge distribution model; Step 3. Calculation of magnetic anomalies generated by topographic surface magnetic charge; Step 4. Topographic correction of magnetic anomalies; Step 5. Magnetic anomaly correlation analysis and residual topographic magnetic anomaly removal; Step 6. Verification and optimization of correction effect. This invention strives to eliminate topographic magnetic anomalies, improves the accuracy and efficiency of topographic correction of magnetic anomalies, eliminates magnetic anomaly distortion caused by topographic undulations and topographic magnetism, restores the true magnetic anomaly signal of underground targets, and provides reliable data support for subsequent geological interpretation and mineral resource exploration.

Description

Technical Field

[0001] This invention relates to the fields of geophysical exploration technology and magnetic anomaly data processing technology, and in particular to a method for topographic correction of magnetic anomalies using the distribution of magnetic charge on the topographic surface. Background Technology

[0002] Magnetic exploration is a core technology in the field of magnetic field measurement in geophysical exploration, and it is also an important application of geomagnetic measurement in mineral resource exploration and geological structure research. In recent years, diamond nitrogen-vacancy center (NV center) magnetic measurement technology, with its advantages of ultra-high sensitivity, high spatial resolution, and strong anti-interference ability, has been gradually applied to high-precision magnetic exploration scenarios, achieving more refined magnetic anomaly signal acquisition and further expanding the application boundaries and detection accuracy of magnetic exploration.

[0003] The core principle of magnetic exploration is based on the magnetic differences in underground strata and rocks. Surface magnetic and geomagnetic measurements are conducted using magnetometers (including traditional proton magnetometers, optically pumped magnetometers, and the emerging NV color center magnetometers). These measurements record changes in the surface magnetic field and geomagnetic anomalies. After data processing, the underground geological structure is inverted, and the distribution of mineral resources is predicted. However, in actual magnetic field measurements and exploration, topographic relief can significantly interfere with magnetic anomaly observations, especially in complex terrains such as mountains and hills. Topographical distortion can mask the true magnetic anomaly signals of underground targets. Furthermore, for high-precision magnetic surveying techniques like NV color centers, even weak magnetic anomaly distortions caused by topographic relief are accurately collected, further amplifying the impact of topographic interference on data interpretation. This leads to deviations in subsequent geological interpretations, affecting the accuracy of magnetic field measurements and geomagnetic exploration.

[0004] Currently, existing technologies for topographic correction of magnetic anomalies mainly fall into two categories: one is the approximate correction method based on "curvature-to-level" conversion, which treats undulating surfaces as horizontal surfaces without considering the magnetic characteristics of the terrain itself. This method can only eliminate part of the influence of geometric undulations and cannot correct the magnetic anomaly distortion caused by the magnetic bodies of the terrain. The correction accuracy is low and it is difficult to meet the exploration needs of high-precision magnetic field and geomagnetic measurements. The other category is the volume integral correction method based on three-dimensional terrain models. This method constructs a three-dimensional terrain cylinder model, calculates and corrects the magnetic anomaly effect caused by the terrain volume, but it suffers from high computational complexity, high hardware computing power requirements, and low computational efficiency. Furthermore, it does not fully utilize the characteristics of magnetic charge distribution on the terrain surface, resulting in redundant calculations during the correction process, which further reduces the processing efficiency and correction accuracy of magnetic field measurement data.

[0005] In existing technologies, such as the invention patent with authorization announcement number CN102236108A, a three-dimensional terrain correction method for magnetic surfaces is disclosed. This method constructs a three-dimensional terrain composite column model, calculates the magnetic anomaly effect value of the columns, and sums them to obtain the correction value. However, this method is still based on volume integral calculations and does not incorporate the core concept of terrain surface magnetic charge distribution. It suffers from high computational load and low efficiency, and it does not adequately utilize the distribution law of magnetic charge on the terrain surface, making it difficult to achieve rapid and accurate correction of magnetic field measurement data under complex terrain. Furthermore, existing methods generally suffer from insufficient detail in characterizing the magnetic susceptibility distribution of the surface strata and inaccurate calculation of magnetic anomaly effects, resulting in certain anomalous distortions after terrain correction, failing to fully restore the true distribution characteristics of underground magnetic targets. In addition, existing calculation methods based on surface magnetic charge mostly use integral forms, which are cumbersome and further reduce the efficiency of geomagnetic measurement data processing. There is an urgent need for a simplified and accurate method for calculating magnetic charge and magnetic anomalies. Moreover, existing methods do not clearly define the calculation logic for the three components of magnetic anomalies and the conversion to the total magnetic anomaly in the direction of the normal geomagnetic field, failing to meet the needs of high-precision magnetic anomaly inversion and magnetic field measurement.

[0006] Furthermore, in high-precision magnetic exploration, especially in mineral resource exploration, the requirements for the accuracy and processing efficiency of magnetic anomaly data correction in magnetic field and geomagnetic measurements are constantly increasing. Existing methods struggle to balance accuracy and efficiency, lack precise calculations of the three components of magnetic anomalies and the total magnetic anomaly converted to the direction of the normal geomagnetic field, and fail to further remove residual topographic magnetic anomalies through relevant analysis, thus failing to completely eliminate topographic interference and failing to meet the needs of actual magnetic field measurement and exploration work. Therefore, there is an urgent need for a magnetic anomaly topographic correction processing method that can fully utilize the characteristics of topographic surface magnetic charge distribution, balance correction accuracy and processing efficiency, clarify the calculation logic of the three components of magnetic anomalies and the total magnetic anomaly converted to the direction of the normal geomagnetic field, and completely eliminate topographic magnetic anomalies through relevant analysis, applicable to complex terrains. Summary of the Invention

[0007] To address the problems of low accuracy, low computational efficiency, insufficient utilization of topographic surface magnetic charge distribution characteristics, difficulty in adapting to complex terrain, cumbersome calculation of surface magnetic charge integrals, lack of calculation logic for the three components of magnetic anomalies and the conversion to the total magnetic anomaly in the direction of the normal geomagnetic field, and failure to remove residual components of topographic magnetic anomalies through relevant analysis and to completely eliminate terrain interference in existing technologies, this invention provides a method for topographic magnetic anomaly correction using topographic surface magnetic charge distribution. By accurately characterizing the distribution features of topographic surface magnetic charge, the magnetic charge of the triangular surface is concentrated at its midpoint. The Coulomb's law for point magnetic charge simplifies the magnetic anomaly calculation process. The calculation logic for the three components of the magnetic anomaly at the measuring point and the conversion to the total magnetic anomaly in the direction of the normal geomagnetic field by the triangular surface magnetic charge is clarified. Relevant analysis steps are added to further remove residual topographic magnetic anomalies, eliminating topographic magnetic anomalies to the greatest extent possible, improving the accuracy and efficiency of topographic magnetic anomaly correction, eliminating magnetic anomaly distortion caused by topographic undulations and topographic magnetism, restoring the true magnetic anomaly signal of underground targets, and providing reliable data support for subsequent geological interpretation and mineral resource exploration.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface includes: Step 1: Collect and preprocess magnetic exploration data, topographic elevation data, geological maps and stratigraphic magnetic statistics of the target work area to obtain the original scalar magnetic anomaly data, the original three-component magnetic anomaly data, the topographic elevation grid data including the outer extension area and the surface stratigraphic magnetic susceptibility distribution grid data for each observation point. Step 2: Based on the terrain elevation grid data, construct a terrain surface model composed of multiple triangular facets. Calculate the magnetic charge density and total magnetic charge of each triangular facet according to the surface stratum magnetic susceptibility distribution grid data and geomagnetic field environment parameters. Concentrate the total magnetic charge of each triangular facet to the midpoint of the triangular facet to form a point magnetic charge. All point magnetic charges constitute the terrain surface magnetic charge distribution model. Step 3: For each observation point, select all point magnetic charges within the influence range of the topographic surface magnetic charge according to the preset influence range of the topographic surface magnetic charge. Use the Coulomb law of point magnetic charge to calculate the contribution value of the three components of the magnetic anomaly generated by each point magnetic charge at the observation point. Add all the contribution values ​​to obtain the total value of the three components of the topographic surface magnetic charge magnetic anomaly at the observation point. Then convert the total value of the three components to the direction of the normal geomagnetic field to obtain the total magnetic anomaly value of the normal geomagnetic field direction at the observation point. Step 4: Overlay the total magnetic anomaly value of the normal geomagnetic field direction at each observation point with the original scalar magnetic anomaly data of that point to obtain the topographically corrected scalar magnetic anomaly data; at the same time, overlay the total value of the three components of the topographic surface magnetic charge magnetic anomaly at each observation point with the original three components of the magnetic anomaly data of that point to obtain the topographically corrected three components of the magnetic anomaly data. Step 5: Calculate the scalar correlation coefficient between the topographically corrected scalar magnetic anomaly data and the original scalar magnetic anomaly data for each observation point, and the component correlation coefficient between each component of the topographically corrected three-component magnetic anomaly data and the corresponding component of the original three-component magnetic anomaly data; identify the data components with residual topographic magnetic anomalies based on the preset correlation coefficient threshold, remove the residues from the data components with residuals using the fitting residual method, and obtain the final magnetic anomaly data of the component; for data components without residuals, directly use the topographically corrected data as the final magnetic anomaly data of the component. Step 6: Select known geological anomaly points within the target work area, and verify the consistency between the final magnetic anomaly data of each component and the known geological anomalies. If the consistency reaches the preset threshold, output the final topographically corrected magnetic anomaly data; otherwise, adjust the relevant calculation parameters and repeat steps 2 to 6.

[0009] In this specification, in step 1: the magnetic exploration data includes the coordinates of each observation point, the scalar magnetic anomaly observation value, and the three-component magnetic anomaly observation values ​​in the x, y, and z directions; the topographic elevation data is obtained by UAV aerial survey or digital elevation model data, with the grid resolution set to 10 meters to 100 meters; the stratigraphic magnetic statistics are obtained by collecting rock samples from the surface strata in the target work area and conducting indoor magnetic susceptibility tests.

[0010] In this specification, when constructing the terrain surface model in step 2, a unit outward normal vector pointing towards the outside of the terrain is also calculated for each triangular facet. When calculating the magnetic charge density of each triangular facet, the geomagnetic field direction vector is first determined based on the geomagnetic tilt and magnetic declination. The dot product of the geomagnetic field direction vector and the unit outward normal vector is calculated to obtain the cosine value of the included angle. Then, the geological magnetic susceptibility value of the area where the triangular facet is located, the average geomagnetic field value in the survey area, and the remanent magnetic induction ratio are obtained. The remanent magnetic induction ratio is added by 1 and then multiplied by the geological magnetic susceptibility value, the average geomagnetic field value, and the cosine value of the included angle.

[0011] In this specification, the coordinates of the midpoint of the triangular facet in step 2 are determined by the average coordinates of the three vertices of the triangular facet; the total magnetic charge of the triangular facet is equal to the magnetic charge density of the triangular facet multiplied by the area of ​​the triangular facet.

[0012] In this specification, when calculating the contribution value of the three components of the magnetic anomaly generated by each point magnetic charge at the observation point using Coulomb's law in step 3, the required parameters include: vacuum permeability, the total magnetic charge of the point magnetic charge, the three components of the unit outward normal vector of the triangular facet containing the point magnetic charge, the spatial distance from the point magnetic charge to the observation point, the difference between the coordinates of the observation point and the coordinates of the midpoint of the point magnetic charge in each direction, and the dot product of the unit outward normal vector and the vector from the point magnetic charge to the observation point.

[0013] In this specification, when converting the total value of the three components of the topographic surface magnetic charge and magnetic anomaly to the total magnetic anomaly value in the direction of the normal geomagnetic field in step 3, the three direction cosines of the direction of the normal geomagnetic field are first determined according to the geomagnetic tilt and magnetic declination. Then, the three direction cosines are multiplied by the x, y, and z components in the total value of the three components of the topographic surface magnetic charge and magnetic anomaly, and then summed.

[0014] In this specification, the calculation formulas for the scalar correlation coefficient and component correlation coefficient in step 5 are as follows: the sum of the products of the difference between the original magnetic anomaly data and its average value of all measuring points and the difference between the topographically corrected magnetic anomaly data and its average value of the corresponding measuring points, divided by the square root of the product of the sum of squares of the deviations of the original magnetic anomaly data and the sum of squares of the deviations of the topographically corrected magnetic anomaly data; the value range of the correlation coefficient threshold is 0.1 to 0.3, which is dynamically adjusted according to the topographic complexity of the target work area and the exploration accuracy requirements.

[0015] In this specification, when removing residual topographic magnetic anomalies from data components in step 5 using the fitting residual method: if the correlation coefficient of the component is greater than or equal to 0.2, a quadratic polynomial nonlinear fitting model is preferred; if the correlation coefficient is less than 0.2, a linear fitting model is used; after the removal is completed, the correlation coefficient between the final magnetic anomaly data and the original magnetic anomaly data is recalculated. If the correlation coefficient of any component is still greater than or equal to the correlation coefficient threshold, the fitting model parameters are adjusted or a nonlinear fitting model is used to repeat the removal until the correlation coefficient of all components is less than the correlation coefficient threshold.

[0016] In this specification, the preset matching threshold mentioned in step 6 is above 90%; while verifying the matching degree, a visual comparison is also made by drawing magnetic anomaly contour maps or profile curves before and after correction, and the positioning error of the final magnetic anomaly data on the underground target body is calculated in combination with geological drilling data to help evaluate the correction effect.

[0017] In this specification, the range of influence of the topographic surface magnetic charge in step 3 is 30 km to 50 km, which is adjusted according to the topographic complexity and exploration accuracy requirements of the target work area; the geomagnetic environment parameters in step 2 are obtained by on-site collection of geomagnetic observation instruments or by calculation using the international geomagnetic reference field model; the process of calculating, superimposing and converting the contribution value of the three components of the magnetic anomaly of the point magnetic charge to the direction of normal geomagnetic field is performed in parallel.

[0018] In summary, the present invention has at least the following beneficial effects: This invention focuses on the distribution of surface magnetic charge on the terrain, replacing the traditional volume integral calculation method. It fully utilizes the distribution patterns of magnetic charge on the terrain surface and innovatively concentrates the magnetic charge of a triangular surface at its midpoint. It then uses Coulomb's law for point magnetic charge to calculate the three components of the magnetic anomaly, and transforms them to the direction of the normal geomagnetic field through dot product operations, obtaining a total magnetic anomaly value that meets actual observation requirements. This invention replaces the traditional surface magnetic charge integral calculation, significantly simplifying the calculation process, reducing computational complexity, and minimizing redundant calculations. While maintaining correction accuracy, it significantly improves processing efficiency and is applicable to magnetic anomaly processing in large-scale complex terrains. It solves the problems of high computational requirements, low efficiency, and cumbersome surface magnetic charge integral calculations in existing volume integral methods. In particular, the efficiency of point magnetic charge magnetic anomaly calculation and transformation to the direction of the normal geomagnetic field is significantly improved compared to the traditional surface magnetic charge integral method. %above( ≥70); at the same time, the calculation logic of the three components of magnetic anomaly and the transformation to the total magnetic anomaly in the direction of the normal geomagnetic field was clarified, and , , Always use the direction cosine of the normal geomagnetic field , , It is stated that the standardization and professionalism of the calculation logic have been further optimized, filling the gap in the lack of relevant calculations in existing methods and meeting the needs of high-precision magnetic anomaly inversion.

[0019] In the calculation of magnetic charge surface density, this invention comprehensively considers the formation magnetic susceptibility. Geomagnetic field environment Remanence ratio Taking into account factors such as the slope angle of the terrain surface, the angle between the geomagnetic field direction and the terrain surface normal vector was determined using a precise method for calculating the out-of-plane normal of a triangular face. The computational logic accurately characterizes the distribution features of the topographic surface magnetic charge; simultaneously, it calculates the three components of the magnetic anomaly using the concentrated magnetic charge at the midpoint of a triangular facet and Coulomb's law for point magnetic charges, then transforms it to the direction of the normal geomagnetic field to obtain the total magnetic anomaly (using direction cosine). , , express , , This method not only ensures the accuracy of magnetic anomaly (three components + total anomaly in the direction of the normal geomagnetic field) calculation, but also simplifies the calculation process, making the calculation of magnetic anomalies generated by the magnetic charge of the terrain surface more accurate and efficient. It effectively eliminates the magnetic anomaly distortion caused by terrain undulation and terrain magnetism, and the correction accuracy is significantly higher than the traditional "curved flattening" method, which can more realistically restore the distribution characteristics of underground magnetic targets.

[0020] This invention adds a magnetic anomaly correlation analysis and residual topographic magnetic anomaly removal step. By calculating the correlation coefficient between the corrected magnetic anomaly and the original magnetic anomaly, residual topographic magnetic anomaly components are accurately identified. Combined with the fitting residual method, residual interference is further removed, eliminating topographic magnetic anomalies to the greatest extent possible. This solves the problem of residual topographic magnetic anomalies and poor land modification effects after correction in existing methods, significantly enhancing the magnetic land modification effect. Through correlation coefficient threshold control and multi-round fitting optimization, the removal of topographic magnetic anomalies is ensured to be thorough, while avoiding over-removal that would lead to the loss of the true magnetic anomaly signal of the underground target body. This further improves the correction accuracy, making the final magnetic anomaly data more closely match the true distribution characteristics of the underground target body.

[0021] This invention includes a verification and optimization step for the correction effect. By combining the final magnetic anomaly data after relevant analysis with known geological anomaly points, geological drilling data, and visualization comparison, the correction parameters, relevant analysis parameters, and fitting model parameters can be dynamically adjusted to ensure that the correction effect meets the actual exploration needs. This improves the applicability and reliability of the method and is suitable for terrain conditions of varying complexity, such as mountains and hills. It can be widely applied in fields such as mineral resource exploration and geological structure research.

[0022] The technical solution of this invention is simple and easy to implement, the data preprocessing process is mature, and the steps for constructing the magnetic charge surface distribution model, calculating magnetic anomalies (three components + total anomaly in the direction of the normal geomagnetic field), correction and related analysis are clear. The derivation of the out-of-plane normal, the calculation of the midpoint coordinates, the calculation of the three components of the point magnetic charge anomaly, the conversion to the direction of the normal geomagnetic field (using the direction cosine to represent the related components) and related analysis, and the residual stripping can all be automatically realized by the program without the need for complex hardware equipment, which is convenient for engineering application and promotion. At the same time, it can be seamlessly connected with the existing magnetic exploration data processing system, reducing the cost of actual application.

[0023] Compared to existing methods for correcting 3D terrain column models, this invention avoids the cumbersome process of column model construction and reduces computational load. Compared to traditional surface magnetic charge integral calculation methods, it simplifies the magnetic anomaly calculation process. Furthermore, through precise calculation of magnetic charge surface density, it overcomes the shortcomings of existing methods in terms of imprecise terrain magnetic characterization, further improving the accuracy and stability of magnetic anomaly terrain correction. In addition, it provides a clear logic for the calculation of the three components of magnetic anomaly and the transformation to the normal geomagnetic field direction (using direction cosine). , , Standard representation , , The addition of related analyses and residual stripping steps can provide richer and more accurate magnetic anomaly information, providing more reliable data support for the precise inversion of underground targets. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0025] Figure 1 This is a schematic diagram of the method for correcting magnetic anomalies in terrain by utilizing the distribution of magnetic charge on the terrain surface involved in this invention.

[0026] Figure 2 This is a plan view of the original aeromagnetic anomaly of the target work area in an embodiment of the present invention.

[0027] Figure 3 This is a topographic elevation map of the target work area in an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the triangular division of the ground elevation in an embodiment of the present invention.

[0029] Figure 5 This is a map showing the distribution of magnetic charge density on the terrain surface in an embodiment of the present invention.

[0030] Figure 6 This is a planar diagram of the area of ​​the triangular facets after triangulation in an embodiment of the present invention.

[0031] Figure 7 This is a diagram showing the magnetic charge distribution of the triangular facets after triangulation in an embodiment of the present invention.

[0032] Figure 8 This is a topographic magnetic anomaly map (total magnetic anomaly) of the normal surface magnetic susceptibility calculated according to the method of the present invention in an embodiment of the present invention.

[0033] Figure 9 This is a residual magnetic anomaly diagram after the first magnetic-geological modification in an embodiment of the present invention.

[0034] Figure 10 This is the second fitted magnetic anomaly map after magnetogeographic modification in an embodiment of the present invention.

[0035] Figure 11 This is a residual magnetic anomaly diagram after the second magnetic-geochemical modification in an embodiment of the present invention.

[0036] Figure 12 This is a fitting diagram of removing residual topographic magnetic anomalies using sliding trend analysis in an embodiment of the present invention.

[0037] Figure 13 This is a correlation coefficient diagram for removing residual topographic magnetic anomalies using sliding trend analysis in an embodiment of the present invention. Detailed Implementation

[0038] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0039] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0040] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] like Figure 1 As shown, this embodiment provides a method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface, including: Step 1: Collect and preprocess magnetic exploration data, topographic elevation data, geological maps and stratigraphic magnetic statistics of the target work area to obtain the original scalar magnetic anomaly data, the original three-component magnetic anomaly data, the topographic elevation grid data including the outer extension area and the surface stratigraphic magnetic susceptibility distribution grid data for each observation point. Step 2: Based on the terrain elevation grid data, construct a terrain surface model composed of multiple triangular facets. Calculate the magnetic charge density and total magnetic charge of each triangular facet according to the surface stratum magnetic susceptibility distribution grid data and geomagnetic field environment parameters. Concentrate the total magnetic charge of each triangular facet to the midpoint of the triangular facet to form a point magnetic charge. All point magnetic charges constitute the terrain surface magnetic charge distribution model. Step 3: For each observation point, select all point magnetic charges within the influence range of the topographic surface magnetic charge according to the preset influence range of the topographic surface magnetic charge. Use the Coulomb law of point magnetic charge to calculate the contribution value of the three components of the magnetic anomaly generated by each point magnetic charge at the observation point. Add all the contribution values ​​to obtain the total value of the three components of the topographic surface magnetic charge magnetic anomaly at the observation point. Then convert the total value of the three components to the direction of the normal geomagnetic field to obtain the total magnetic anomaly value of the normal geomagnetic field direction at the observation point. Step 4: Overlay the total magnetic anomaly value of the normal geomagnetic field direction at each observation point with the original scalar magnetic anomaly data of that point to obtain the topographically corrected scalar magnetic anomaly data; at the same time, overlay the total value of the three components of the topographic surface magnetic charge magnetic anomaly at each observation point with the original three components of the magnetic anomaly data of that point to obtain the topographically corrected three components of the magnetic anomaly data. Step 5: Calculate the scalar correlation coefficient between the topographically corrected scalar magnetic anomaly data and the original scalar magnetic anomaly data for each observation point, and the component correlation coefficient between each component of the topographically corrected three-component magnetic anomaly data and the corresponding component of the original three-component magnetic anomaly data; identify the data components with residual topographic magnetic anomalies based on the preset correlation coefficient threshold, remove the residues from the data components with residuals using the fitting residual method, and obtain the final magnetic anomaly data of the component; for data components without residuals, directly use the topographically corrected data as the final magnetic anomaly data of the component. Step 6: Select known geological anomaly points within the target work area, and verify the consistency between the final magnetic anomaly data of each component and the known geological anomalies. If the consistency reaches the preset threshold, output the final topographically corrected magnetic anomaly data; otherwise, adjust the relevant calculation parameters and repeat steps 2 to 6.

[0042] In some embodiments, in step 1: the magnetic exploration data includes the coordinates of each observation point, scalar magnetic anomaly observation values, and three-component magnetic anomaly observation values ​​in the x, y, and z directions; the topographic elevation data is acquired using UAV aerial surveying or digital elevation model data, with a grid resolution set to 10 to 100 meters; the stratigraphic magnetic statistics are obtained by collecting rock samples from various surface strata in the target work area and conducting indoor magnetic susceptibility tests.

[0043] In some embodiments, when constructing the terrain surface model in step 2, a unit outward normal vector pointing outward from the terrain is also calculated for each triangular facet. When calculating the magnetic charge density of each triangular facet, the geomagnetic field direction vector is first determined based on the geomagnetic tilt and magnetic declination. The dot product of the geomagnetic field direction vector and the unit outward normal vector is calculated to obtain the cosine value of the included angle. Then, the stratigraphic magnetic susceptibility value, the average geomagnetic field value in the survey area, and the remanent magnetic induction ratio of the area where the triangular facet is located are obtained. The remanent magnetic induction ratio is added by 1 and then multiplied by the stratigraphic magnetic susceptibility value, the average geomagnetic field value, and the cosine value of the included angle.

[0044] In some embodiments, the coordinates of the midpoint of the triangular facet in step 2 are determined by the average coordinates of the three vertices of the triangular facet; the total magnetic charge of the triangular facet is equal to the magnetic charge density of the triangular facet multiplied by the area of ​​the triangular facet.

[0045] In some embodiments, when calculating the contribution value of the three components of the magnetic anomaly generated by each point magnetic charge at the observation point using Coulomb's law in step 3, the required parameters include: vacuum permeability, the total magnetic charge of the point magnetic charge, the three components of the unit outward normal vector of the triangular facet containing the point magnetic charge, the spatial distance from the point magnetic charge to the observation point, the difference between the coordinates of the observation point and the coordinates of the midpoint of the point magnetic charge in each direction, and the dot product of the unit outward normal vector and the vector from the point magnetic charge to the observation point.

[0046] In some embodiments, when converting the total value of the three components of the topographic surface magnetic charge and magnetic anomaly to the total magnetic anomaly value in the direction of the normal geomagnetic field in step 3, the three direction cosines of the direction of the normal geomagnetic field are first determined according to the geomagnetic tilt and magnetic declination, and then the three direction cosines are multiplied by the x, y, and z components in the total value of the three components of the topographic surface magnetic charge and magnetic anomaly and then summed.

[0047] In some embodiments, the calculation formulas for the scalar correlation coefficient and the component correlation coefficient in step 5 are both: the sum of the products of the difference between the original magnetic anomaly data and its average value of all measuring points and the difference between the topographically corrected magnetic anomaly data and its average value of the corresponding measuring points, divided by the square root of the product of the sum of squares of the deviations of the original magnetic anomaly data and the sum of squares of the deviations of the topographically corrected magnetic anomaly data; the value range of the correlation coefficient threshold is 0.1 to 0.3, and it is dynamically adjusted according to the topographic complexity of the target work area and the exploration accuracy requirements.

[0048] In some embodiments, when using the fitting residual method to remove residual data components with residual topographic magnetic anomalies in step 5: when the correlation coefficient of the component is greater than or equal to 0.2, a quadratic polynomial nonlinear fitting model is preferred; when the correlation coefficient is less than 0.2, a linear fitting model is used; after the removal is completed, the correlation coefficient between the final magnetic anomaly data after removal and the original magnetic anomaly data is recalculated. If the correlation coefficient of any component is still greater than or equal to the correlation coefficient threshold, the fitting model parameters are adjusted or a nonlinear fitting model is used to repeat the removal until the correlation coefficient of all components is less than the correlation coefficient threshold.

[0049] In some embodiments, the preset matching threshold in step 6 is above 90%; while verifying the matching degree, a visual comparison is also made by drawing magnetic anomaly contour maps or profile curves before and after correction, and the positioning error of the final magnetic anomaly data on the underground target body is calculated in combination with geological drilling data to help evaluate the correction effect.

[0050] In some embodiments, the range of influence of the topographic surface magnetic charge in step 3 is 30 km to 50 km, which is adjusted according to the topographic complexity and exploration accuracy requirements of the target work area; the geomagnetic environment parameters in step 2 are obtained by on-site collection of geomagnetic observation instruments or by calculation using the international geomagnetic reference field model; the process of calculating, superimposing and converting the contribution value of the three components of the magnetic anomaly of the point magnetic charge to the direction of normal geomagnetic field is performed in parallel.

[0051] The technical concept of this invention is as follows: Data Acquisition and Preprocessing: Magnetic exploration data, topographic elevation data, geological maps, and stratigraphic magnetic statistics were collected from the target work area. The collected data underwent preprocessing to obtain raw magnetic anomaly data for the measuring points, topographic elevation grid data for the work area and its extension area, and surface stratigraphic magnetic susceptibility distribution grid data. The preprocessing included data denoising, coordinate unification, grid interpolation, and anomaly separation. The surface stratigraphic magnetic susceptibility distribution grid data was obtained by assigning different stratigraphic layers to their corresponding magnetic susceptibility values ​​on the geological map and then correcting this data using stratigraphic magnetic statistics to ensure consistency between the magnetic susceptibility distribution and the actual stratigraphic layers. The magnetic exploration data included... There are 1 observation points, and the distance between the observation points is 1 / 2. The terrain elevation data grid resolution is set to... In the stratigraphic magnetic statistics, the average magnetic susceptibility of different stratigraphic layers is as follows: , … .

[0052] Construction of the Magnetic Charge Distribution Model of the Terrain Surface: Based on the preprocessed terrain elevation grid data, a three-dimensional terrain surface model of the target work area is constructed; the three-dimensional terrain surface is constructed using a triangular mesh (TIN), and the outward normal vector of each triangular facet is obtained through the vertex spatial coordinates. The specific steps are as follows: ① Take the three vertices of the triangular facet. , , Construct edge vectors , ② Calculate the cross product of two vectors. The initial normal vector is obtained, and its components are as follows: , , ③ By determining the initial normal vector and the vertically upward unit vector For the dot product of (0,0,1), the normal vector direction is uniformly adjusted to point outwards from the terrain, with upwards being positive. If the dot product... If the value is less than 0, then invert the initial normal vector, which means inverting each component of the original vector; ④ Normalize the adjusted normal vector to obtain the unit outward normal vector of the triangular facet. (in (This refers to the vector magnitude). Based on the magnetic susceptibility distribution grid data of the surface strata and combined with geomagnetic field environmental parameters, the magnetic charge density of each triangular facet on the terrain surface is calculated; geomagnetic field direction vector. Due to geomagnetic tilt , deflection angle Confirmed, the expression is =(cosIcosD,cosIsinD,sinI), the angle between the direction of the geomagnetic field and the outward normal of the terrain. satisfy The calculation of magnetic charge surface density takes into account the geomagnetic field strength, the magnetic susceptibility of the formation, and the remanence ratio. The specific calculation formula is as follows: ,in, , is the magnetic surface charge density The remanence ratio (range 0.1-2.0) This represents the magnetic susceptibility value of the strata in the region where the triangular facet is located. This represents the average geomagnetic field value within the survey area. Let be the angle between the direction of the geomagnetic field and the normal vector of the terrain surface. Calculate the area of ​​each triangular facet. According to the magnetic surface charge density With area Calculate the total magnetic charge of the triangular facet. Find the coordinates of the midpoint of each triangular facet. Midpoint (x-midpoint, y-midpoint, z-midpoint), the formula for calculating the midpoint coordinates is x-midpoint = y midpoint = midpoint of z = The total magnetic charge of each triangular facet Concentrate at its midpoint The midpoint forms a point magnetic charge distribution. Based on the point magnetic charge distribution of all triangular facets, a terrain surface magnetic charge distribution model is constructed.

[0053] Calculation of magnetic anomaly generated by topographic surface magnetic charge: For each magnetic anomaly observation point, determine the influence range of the corresponding topographic surface magnetic charge (range 30-50km); based on the topographic surface magnetic charge distribution model, select the midpoints of all triangular patches within the influence range (i.e., the locations of the point magnetic charge), and use the Coulomb's law of point magnetic charge to calculate the magnetic anomaly contribution value (including three components) generated by each point magnetic charge at the observation point; superimpose the magnetic anomaly contribution values ​​(including three components) of all point magnetic charge separately to obtain the three component values ​​of the topographic surface magnetic charge magnetic anomaly at the observation point, and then convert the three components of the magnetic anomaly to the direction of the normal geomagnetic field to obtain the total magnetic anomaly value in the direction of the normal geomagnetic field; The calculation formulas for point magnetic charge using Coulomb's law and the conversion formulas for the three components of magnetic anomaly to the direction of the normal geomagnetic field are both derived based on magnetic charge theory, taking into account the spatial relationship between the point magnetic charge and the observation point, as well as the directional characteristics of the normal geomagnetic field, as detailed below: (1) Formula for calculating the three components (x, y, z directions) of magnetic anomaly generated by a single point magnetic charge at the observation point: ; ; ; in, , , These represent the contribution components of magnetic anomalies in the x, y, and z directions generated by a single point magnetic charge at the observation point. The permeability of free space, Let be the total magnetic charge concentrated at the midpoint of the triangular facet. , , These are the unit outward normal vectors of the triangular facets. The x, y, and z components, The distance from the point magnetic charge (midpoint of the triangular facet) to the observation point is given. The vector is the vector from the point magnetic charge to the observation point (i.e., (x measurement point - x midpoint, y measurement point - y midpoint, z measurement point - z midpoint)). Outer normal vector and The dot product of vectors Spatial distance 5th power; (2) Spatial distance The calculation formula is as follows: Where x, y, and z are the three-dimensional coordinates of the observed points, and x, y, and z are the three-dimensional coordinates of the midpoint of the triangular patch. (3) Formula for calculating the three components of magnetic anomaly generated by all point magnetic charges at the observation points: Let the direction cosines of the normal geomagnetic field be respectively , , (in The unit vector corresponding to the normal geomagnetic field direction of Quantity ; ,correspond y component ; ,correspond of Quantity Then, the three components of the magnetic anomaly generated by all point magnetic charges at the observation points can be expressed as: ; ; ; in, To determine the number of point magnetic charges within the affected area, , , The first The contribution components of magnetic anomalies in the x, y, and z directions of a point magnetic charge. , , These represent the total magnetic anomaly components in the x, y, and z directions generated by all point magnetic charges at the observation points. Let be the total magnetic charge at the i-th point. , , These are the unit outward normal vectors of the i-th triangular facet. The x, y, and z components, Let be the spatial distance from the magnetic charge at point i to the observation point. vector Let be the vector of the magnetic charge at point i from the observation point. vector Let i be the outward normal vector of the i-th triangle. and The dot product of vectors ᵢ; (4) Formula for calculating the total magnetic anomaly value after the three components of the magnetic anomaly are converted to the direction of the normal geomagnetic field: ; in, This represents the total magnetic anomaly value generated by the triangular magnetic charge at the measuring point and transformed into the direction of the normal geomagnetic field. The unit vector representing the direction of the normal geomagnetic field (derived from the geomagnetic dip angle). , deflection angle It is determined that their direction cosines are respectively , , ), ( , , )ᵀ is the transpose of the three-component vector of magnetic anomalies generated by all point magnetic charges at the observation points. , , These are the three direction cosines of the normal geomagnetic field direction. Essentially, this formula is the dot product of the three components of the magnetic anomaly vector and the unit vector of the normal geomagnetic field direction. It projects the three components of the three-dimensional magnetic anomaly onto the normal geomagnetic field direction to obtain the total magnetic anomaly value that meets the actual observation requirements.

[0054] Magnetic anomaly topographic correction: The total magnetic anomaly value of the topographic surface magnetic charge converted to the normal geomagnetic field direction for each observation point. Compared with the preprocessed original magnetic anomaly data of this measuring point Superposition correction is performed to obtain the topographically corrected magnetic anomaly data (scalar); at the same time, the topographic surface magnetic charge magnetic anomaly three-component values ​​are superimposed and corrected with the original magnetic anomaly three-component data (acquired synchronously during preprocessing) to obtain the topographically corrected magnetic anomaly three-component data. The correction formula is as follows: (1) Scalar magnetic anomaly correction formula: ; (2) Three-component magnetic anomaly correction formula: ; ; ; in, This is the topographically corrected scalar magnetic anomaly data. This is the preprocessed scalar raw magnetic anomaly data; ΔT x Correction, ΔTᵧ correction, Δ The corrections are applied to the topographically corrected magnetic anomaly components in the x, y, and z directions. , , These are the preprocessed raw magnetic anomaly data in the x, y, and z directions. , , These are the three direction cosines of the normal geomagnetic field direction.

[0055] Magnetic anomaly correlation analysis and residual topographic magnetic anomaly removal: To eliminate topographic magnetic anomalies to the greatest extent possible and enhance the magnetic correction effect, the topographically corrected magnetic anomaly data (scalar + three components) obtained in step 4 is compared with the original magnetic anomaly data (scalar) to be corrected. and three components ΔT x Original, ΔTᵧ original, Δ The original data is subjected to correlation analysis. By calculating the correlation, residual topographic magnetic anomaly components are identified, and topographic interference is further removed. The specific steps are as follows: (1) Correlation calculation: Calculate the correlation coefficients between the scalar and three-component corrected magnetic anomalies and the original magnetic anomalies, respectively. Correlation coefficient of x-direction components y-direction component correlation coefficient z-direction component correlation coefficient The formula for calculating the correlation coefficient is: ;in, Let X be the raw magnetic anomaly data (scalar or a component) of the i-th measuring point, and let ĒX be the average value of the raw magnetic anomaly data of all measuring points. The topographically corrected magnetic anomaly data for the i-th measuring point (corresponding scalar or the same component). The average value of the topographically corrected magnetic anomaly data for all measuring points; correlation coefficient. The value range of is [-1, 1]. The closer the absolute value is to 1, the stronger the correlation between the two and the more residual topographic magnetic anomaly components there are. The closer the absolute value is to 0, the more thoroughly the topographic magnetic anomaly has been eliminated.

[0056] (2) Identification of residual topographic and magnetic anomalies: setting a correlation coefficient threshold (Values ​​range from 0.1 to 0.3, determined based on the complexity of the terrain and the required exploration accuracy in the work area.) If the correlation coefficient of a certain component... This indicates that the component still has significant residual topographic magnetic anomalies and requires further stripping; if This indicates that the geomagnetic anomaly in this component has been largely eliminated and no further processing is required.

[0057] (3) Residual topographic and magnetic anomaly removal: For components with residual topographic and magnetic anomalies, a linear fitting model is constructed using the residual fitting method, with the original magnetic anomaly data as the independent variable and the corrected magnetic anomaly data as the dependent variable. ( These are the fitting coefficients. (where ε is the intercept), calculate the fitting residual ε. The residual is the final magnetic anomaly data after removing the residual topographic magnetic anomaly; for components without residual topographic magnetic anomalies, the corrected magnetic anomaly data is directly used as the final magnetic anomaly data. The final magnetic anomaly data (scalar + three components) is calculated using the following formula: when hour, , , , ; when hour, = , = , , ; in, , , , The fitting residuals for the scalar and ternary quantities are respectively obtained by calculating using the above fitting formula.

[0058] (4) Correlation verification: For the final magnetic anomaly data after removing residual topographic magnetic anomalies, the correlation coefficient is calculated again with the original magnetic anomaly data. If the correlation coefficient of all components is less than r0, it indicates that the topographic magnetic anomaly has been eliminated to the greatest extent; if there are still components with a correlation coefficient ≥ Repeat steps 2-3, adjusting the fitting model parameters (or using a nonlinear fitting model), until all component correlation coefficients meet the requirements. This ensures optimal results in eliminating topographic magnetic anomalies.

[0059] Verification and optimization of correction effect: Known geological anomaly points in the target work area are selected as verification points. The final magnetic anomaly data (scalar + three components) after stripping residual topographic magnetic anomalies and the magnetic anomaly data after initial correction are compared with the known geological anomalies. If the final magnetic anomaly data does not reach the preset threshold (≥90%), the influence range of topographic surface magnetic charge, the calculation parameters of magnetic charge surface density, the correlation coefficient in the calculation of point magnetic charge magnetic anomalies, and the correlation analysis threshold are adjusted. 1. Fit the model parameters, repeat steps 2-5 until the correction effect meets the preset requirements; if the fit reaches the preset threshold, output the final topographically corrected magnetic anomaly data (scalar + three components), completing the magnetic anomaly topographic correction processing. Known geological anomaly points are selected... , initial fit is After adjusting the parameters, the fit is ( ≥90%).

[0060] Furthermore, in step 1, the magnetic exploration data includes the coordinates of the measuring points and the observed magnetic anomalies (including scalars and x, y, and z components). The topographic elevation data is obtained using UAV aerial surveying or DEM data, with a grid resolution of [missing information]. The depth is set to 10-100m based on the required exploration accuracy. The stratigraphic magnetic statistics are obtained through field rock sample collection and indoor magnetic susceptibility testing. S sets of rock samples are collected to ensure the magnetic susceptibility value of each stratigraphic layer is accurate. , … This data is representative; during preprocessing, the original three-component magnetic anomaly data is simultaneously denoised, coordinate unified, and anomaly separated to obtain the original three-component magnetic anomaly data. , , .

[0061] Furthermore, in step 2, the geomagnetic field environment parameters include geomagnetic field strength and direction, which are collected on-site by geomagnetic observation instruments or using regional geomagnetic background data to ensure the accuracy of the magnetic charge surface density calculation; the determination of the outward normal of the triangular facet and the area of ​​the triangular facet. Calculate the coordinates of the midpoint. Midpoint determination and total magnetic charge The calculation process can be automated by the program, ensuring that the calculation of the normal vector of the three-dimensional terrain surface model and the construction of the point magnetic charge distribution are accurate and efficient, and are suitable for large-scale terrain data processing.

[0062] Furthermore, in step 3, the influence range of the topographic surface magnetic charge is determined based on the topographic complexity and exploration accuracy requirements of the target work area. The greater the topographic undulation and the higher the exploration accuracy requirements, the larger the influence range value. The calculation of the contribution component of the point magnetic charge magnetic anomaly, the superposition of the three components of the magnetic anomaly, and the transformation to the direction of the normal geomagnetic field are performed in parallel to improve computational efficiency and are suitable for large-scale three-dimensional topographic data processing. The calculation formula is: .

[0063] Further, in step 5, the correlation coefficient threshold... The adjustments can be made dynamically based on the actual conditions of the work area. The more dramatic the terrain undulations and the more uneven the magnetic properties of the strata, the better. The value can be appropriately reduced (0.1-0.2) to ensure that residual topographic magnetic anomalies are fully stripped away; the terrain is relatively flat and the strata have uniform magnetism. The value can be appropriately increased (0.2-0.3) to avoid excessive stripping leading to the loss of the true magnetic anomaly signal of the underground target; the fitting model can be selected as linear or nonlinear fitting according to the correlation coefficient. When the value is ≥0.2, nonlinear fitting models (such as quadratic polynomial fitting) should be used first to improve the accuracy of residual calculation and ensure the effect of residual topographic magnetic anomaly stripping.

[0064] Furthermore, in step 6, the verification of the correction effect can also be achieved by drawing magnetic anomaly contour maps (scalar + three components) and profile curves before and after correction, to visually compare the elimination effect of terrain distortion. Simultaneously, combined with geological drilling data, the accuracy of the corrected magnetic anomaly data (scalar + three components) in reflecting the underground target body can be verified, wherein the positioning error of the underground target body is ≤ In addition, the root mean square error between the final magnetic anomaly data and the known geological anomalies can be calculated to help verify the correction effect. The smaller the root mean square error, the higher the correction accuracy and the more thorough the elimination of topographic and magnetic anomalies.

[0065] In one specific embodiment: Step 1. Data Acquisition and Preprocessing: 1.1 Collect magnetic exploration data of the target work area, including the coordinates (x, y, h) of N observation points and magnetic anomaly observations (including scalar and x, y, z components), with an interval of L between observation points; collect data of the work area and its surrounding areas. DEM topographic elevation data for the range, with grid resolution set to [value missing]. , The exploration accuracy was set to 10-100m; geological maps and stratigraphic magnetic statistics of the work area were collected; rock samples from Group S were collected in the field; and the average magnetic susceptibility of surface strata in various locations was measured indoors. When magnetic data of surface geological bodies in the field is insufficient or lacking, the magnetic susceptibility of the entire area is often defined as a constant. In subsequent magnetic topographic correction, there is a further correlation analysis process for the absence of surface magnetic data, so as to achieve good magnetic topographic correction results under the constraint of no surface magnetic data.

[0066] 1.2 Data Preprocessing: Wavelet filtering was used to denoise the magnetic exploration data (scalar + three components) and remove random interference; all data were uniformly converted to a specified coordinate system; Kriging interpolation was used to perform grid interpolation on the topographic elevation data and magnetic susceptibility data to obtain uniform grid topographic elevation data and surface stratum magnetic susceptibility distribution grid data; Trend analysis was used to separate regional magnetic anomalies and local magnetic anomalies to obtain the original magnetic anomaly data (scalar + three components) of the measuring points. and three components , , ).

[0067] After completing the data acquisition and preprocessing in step 1, the raw aeromagnetic anomaly data for the target work area is obtained. For example... Figure 2 As shown, the measured aeromagnetic anomalies in the WTS area are strongly interfered with by the surface Archean strongly magnetic metamorphic rocks. The anomaly morphology is complex and the local fluctuations are violent. The effective magnetic anomaly signals of the deep geological bodies are significantly masked, and magnetic anomaly topographic correction processing is necessary.

[0068] Step 2. Construction of the topographic surface magnetic charge distribution model: 2.1 Based on the preprocessed terrain elevation grid data, a triangular mesh modeling method is used to construct a three-dimensional terrain surface model of the target work area, accurately depicting the undulating features of the mountains, including terrain details such as peaks and valleys; the outward normal vector of each triangular facet is obtained through the following steps: ① Select any triangular facet and determine the coordinates of its three vertices. , , ② Construct edge vectors , ③ Calculate the cross product ④ Calculation and dot product ,like If it is determined to be an external normal, no inversion is needed; if ⑤ Invert the initial normal vector; ⑥ Calculate Length of the module Normalization yields n ),in , , Outer normal vector The x, y, and z components.

[0069] Based on the preprocessed terrain elevation grid data, a three-dimensional terrain surface model of the target work area is constructed. For example... Figure 3 As shown, the terrain in this area is highly undulating with significant elevation differences and complex slope variations. It is essential to accurately characterize the terrain features to ensure the accuracy of subsequent magnetic charge distribution calculations.

[0070] The terrain elevation data was triangulated using an irregular triangular network (TIN), and the triangulation results are shown below. Figure 4 As shown, a triangular mesh is overlaid on the topographic base map. The geometry and spatial position of each triangular mesh are accurately recorded, providing a basic model for subsequent magnetic charge surface density calculation and point magnetic charge distribution construction.

[0071] 2.2 Collect geomagnetic field environmental parameters within the survey area and measure the average geomagnetic field value. Geomagnetic field dip angle , deflection angle Determine the direction cosine of the normal geomagnetic field =cosIcosD、 =cosIsinD、 =sinI (corresponding to the unit vector of the normal geomagnetic field direction) x, y, z components , , ); Calculate the angle between the direction of the geomagnetic field and the outward normal of the terrain. , Set the remanence ratio (This can be determined through magnetic measurements. If no magnetic data is available, a setting can be made manually and then modified based on the magnetic topography correction.) The magnetic charge surface density is calculated using the formula... Calculate the surface magnetic charge density of the strata in each surface region. It represents the magnetic susceptibility of the Earth's surface strata.

[0072] 2.3 Calculate the area of ​​the selected triangular facet The edge vector of the triangular facet , Vector magnitude , Angle between two vectors of , Therefore, the area of ​​the triangular facet .

[0073] 2.4 Calculate the total magnetic charge of each triangular facet. Find the coordinates of the midpoints of each triangular facet. Midpoint, x midpoint = y midpoint = midpoint of z = ,Right now Midpoint (x midpoint, y midpoint, z midpoint), the total magnetic charge Concentrated at the midpoint, forming a point magnetic charge.

[0074] According to the formula for calculating magnetic surface charge density By combining the magnetic susceptibility distribution of various surface strata, geomagnetic field environmental parameters, and the outward normal direction of the triangular facets, the magnetic charge density of each triangular facet is calculated. For example... Figure 5 As shown, due to the large magnetic inclination angle in the WTS region ( =68°), the magnetic charge surface density in most areas is negative, and the distribution of magnetic charge surface density is closely related to the topographic aspect, slope and stratum magnetization.

[0075] Further calculate the area of ​​each triangular facet, such as Figure 6 As shown, the area of ​​the triangular facets varies in different terrain regions. The area of ​​the triangular facets is relatively small in steep terrain regions and relatively large in gentle terrain regions.

[0076] Multiplying the magnetic charge density of each triangular facet by its area yields the total magnetic charge of that facet. The total magnetic charge distribution is as follows: Figure 7 As shown, areas with larger magnetic charge mainly correspond to areas with higher magnetic susceptibility and steeper terrain slopes.

[0077] 2.5 Following the steps above, calculate the magnetic charge density and area of ​​all triangular facets in sequence. Total magnetic charge and midpoint coordinates The midpoint represents the total magnetic charge of each triangular facet. By focusing on the midpoint, a topographic surface magnetic charge distribution model is constructed, which clearly presents the spatial distribution characteristics of the magnetic charge at the topographic surface, providing a foundation for subsequent magnetic anomaly (three components + total anomaly in the direction of the normal geomagnetic field) calculations.

[0078] Step 3. Calculation of magnetic anomalies generated by topographic surface magnetic charge: 3.1 Determine the influence range of topographic surface magnetic charge at each observation point as follows: (Based on the complexity of the terrain and the required exploration accuracy in the work area), all midpoints of triangular facets within the influence range (i.e., the locations of point magnetic charges) are selected. The number of point magnetic charges within the influence range is set as follows: .

[0079] 3.2 Select any observation point with coordinates (x-point, y-point, z-point) and calculate the magnetic charge at that point relative to the point determined in step 2.4. Spatial distance between midpoints (x-midpoint, y-midpoint, z-midpoint) According to the formula Calculated Simultaneous calculation .

[0080] 3.3 The three components of the magnetic anomaly produced by a single point magnetic charge at the observation point are calculated using the Coulomb's law formula for point magnetic charges. The formula is as follows: ; ; ; Substitution , , , , (x measurement point - x midpoint), (y measurement point - y midpoint), (z measurement point - z midpoint) The calculated vector values ​​yield the magnetic anomaly contribution components in the x, y, and z directions of the magnetic charge at that point. , , .

[0081] 3.4 Parallel computing is used to calculate the impact range sequentially. The three components of the magnetic anomaly generated by the magnetic charge at each observation point are superimposed to obtain the three components of the topographic surface magnetic charge and magnetic anomaly at that observation point. This is then combined with the cosine of the normal geomagnetic field direction. , , The calculation formula is as follows: ; ; ; in, Δ , These are the magnetic anomaly contribution components in the x, y, and z directions of the magnetic charge at the i-th point, respectively. Let be the total magnetic charge at the i-th point. , , These are the unit outward normal vectors of the i-th triangular facet. The x, y, and z components, Let be the spatial distance from the magnetic charge at point i to the observation point. vector Let be the vector of the magnetic charge at point i from the observation point. vector Let i be the outward normal vector of the i-th triangle. and vector The dot product; 3.5 The three components of the magnetic anomaly are transformed to the direction of the normal geomagnetic field to obtain the total magnetic anomaly value in the direction of the normal geomagnetic field. This is then combined with the cosine of the normal geomagnetic field direction. , , The conversion formula is as follows: ; in, , , (From the geomagnetic tilt angle in step 2.2) (Determine the deflection angle D), substitute into , , and , , The total calculated value is the total magnetic anomaly value generated by the triangular magnetic charge at the measuring point and converted into the direction of the normal geomagnetic field; Similarly, calculating the three components of the topographic surface magnetic charge and magnetic anomaly at all observation points, as well as the total magnetic anomaly value converted to the normal geomagnetic field direction, improves computational efficiency compared to the traditional surface magnetic charge integration method. %above.

[0082] The contribution of all point magnetic charges to the magnetic anomaly at the observation points is calculated using Coulomb's law for point magnetic charges, and then superimposed to obtain the total magnetic anomaly generated by the topographic surface magnetic charge. For example... Figure 8 As shown, this is a topographic magnetic anomaly map (total field magnetic anomaly) of the normal surface magnetic susceptibility calculated according to the method of the present invention. The anomaly clearly reflects the topographic undulation and magnetic anomaly distortion characteristics generated by the surface magnetic body. The anomaly amplitude variation is strongly correlated with the topographic elevation variation.

[0083] Step 4. Magnetic anomaly terrain correction: Based on the correction formula, the target magnetic anomaly and the three-component magnetic anomaly are superimposed and corrected separately to obtain the topographically corrected magnetic anomaly data (scalar + three components), which is then combined with the cosine of the normal geomagnetic field direction. , , The specific formula is as follows: 1. Scalar magnetic anomaly correction: ; 2. Three-component magnetic anomaly correction: ; ; ; in, This is the preprocessed scalar raw magnetic anomaly data for this measuring point. , , These are the x, y, and z component data of the original magnetic anomaly at the measuring point after preprocessing. This is the topographically corrected scalar magnetic anomaly data. , , These are the topographically corrected magnetic anomaly components in the x, y, and z directions; To convert the total magnetic anomaly value of the topographic surface magnetic charge to the normal geomagnetic field direction, , , These are the three direction cosines of the normal geomagnetic field direction.

[0084] The calculated total magnetic anomaly value of the topographic surface magnetic charge is superimposed and corrected with the original magnetic anomaly data to obtain the residual magnetic anomaly after the first geomagnetic correction. For example... Figure 9 As shown, after the first geomagnetic alteration, most of the magnetic anomaly distortions caused by topography have been eliminated, and the magnetic anomaly characteristics of deep geological bodies have begun to appear. However, some residual topographic magnetic anomalies still exist in some areas, requiring further analysis and residual stripping.

[0085] Step 5. Correlation analysis of magnetic anomalies and removal of residual topographic magnetic anomalies: 5.1 Correlation Calculation: Calculate the correlation coefficients between the scalar and three-component corrected magnetic anomalies and the original magnetic anomalies, i.e., the scalar correlation coefficients. Correlation coefficient of x-direction components y-direction component correlation coefficient z-direction component correlation coefficient Substitute into the correlation coefficient calculation formula: , where Xᵢ represents the original magnetic anomaly data (scalar or corresponding component) of each measuring point. This represents the average value of the original magnetic anomaly data; The corrected magnetic anomaly data (corresponding scalar or component) for each measuring point. This represents the average value of the corrected magnetic anomaly data; calculated as follows: =0.28、 =0.32、 =0.15、 =0.21.

[0086] 5.2 Residual Topographic Magnetic Anomaly Identification: Considering the characteristics of the work area, such as dramatic topographic relief and heterogeneous stratigraphic magnetic properties, a correlation coefficient threshold was set. =0.2, compared with the calculated correlation coefficient, =0.32≥0.2, indicating that there is a significant residual topographic magnetic anomaly in the x-direction component, which needs to be further stripped; =0.28≥0.2, the scalar magnetic anomaly has residual topographic magnetic anomaly, which needs to be further stripped away; =0.15<0.2、 =0.21≈0.2, the topographic magnetic anomalies in the y and z directions have been basically eliminated and no further processing is required.

[0087] To eliminate the residual topographic and magnetic anomalies after the first geomagnetic correction, correlation analysis was performed between the corrected magnetic anomaly data and the original magnetic anomaly data. For example... Figure 12 As shown in the figure, the goodness-of-fit diagram of the correlation analysis between the topographic magnetic anomaly obtained by the sliding trend analysis and the residual magnetic anomaly after the first geomagnetic alteration shows that there is a certain degree of correlation between the two, and the goodness-of-fit curve shows obvious trend characteristics.

[0088] like Figure 13 As shown, the correlation coefficient distribution map further quantitatively demonstrates the degree of correlation between the corrected magnetic anomaly and the original magnetic anomaly in different regions and components. The regions with higher correlation coefficients are the regions with more obvious residual topographic magnetic anomalies, which need to be separated by fitting residual method.

[0089] 5.3 Residual Topographic Magnetic Anomaly Stripping: For the x-axis component and scalar magnetic anomaly, a quadratic polynomial nonlinear fitting model was used, with the original magnetic anomaly data as the independent variable and the corrected magnetic anomaly data as the dependent variable, to construct the fitting model. ( , These are the fitting coefficients. (where the intercept is the variable), calculate the fitting residuals for the scalar and x-direction components respectively. , ,Right now , ,in , , These are the scalar fitting coefficients and intercept. , , Here are the fitting coefficients and intercepts for the x-direction component; for the y and z-direction components, the corrected magnetic anomaly data is directly used as the final magnetic anomaly data for the corresponding components. , .

[0090] A quadratic polynomial nonlinear fitting model was used to calculate the fitting residuals for components with residual topographic magnetic anomalies. These fitting residuals were then used as the final magnetic anomaly data after removing the residual topographic magnetic anomalies. Figure 10 As shown, this is the magnetic anomaly map after the second fitting of the magnetogeographic modification, and... Figure 8 In comparison, after relevant analysis and residual stripping, the interference of topographic magnetic anomalies was further eliminated, and the anomaly morphology became smoother and more continuous.

[0091] like Figure 11As shown, this is a residual magnetic anomaly map after the second magnetogeographic alteration. This residual anomaly reflects the distribution characteristics of deep magnetic geological bodies in the WTS area well and highlights the stratigraphic boundaries that are difficult to identify within the Archean strata.

[0092] 5.4 Correlation Verification: The correlation coefficient between the final magnetic anomaly data after removing residual data and the original magnetic anomaly data was calculated again to obtain... =0.17、 =0.18、 =0.14、 =0.20, all component correlation coefficients are less than 0.20. =0.2, indicating that the topographic magnetic anomaly has been eliminated to the greatest extent and no further fitting optimization is needed.

[0093] Step 6. Verification and optimization of calibration results: 6.1 Selecting the work area Using known geological anomalies as verification points, the final magnetic anomaly data (scalar + three components) after stripping residual topographic magnetic anomalies, the magnetic anomaly data after initial correction, and the known geological anomalies were compared to assess their agreement. The initial agreement was [value missing]. =82%, which does not meet the preset threshold (≥90%).

[0094] 6.2 Adjust the influence range of topographic surface magnetic charge to Adjust the remanent magnetic induction ratio to At the same time, adjust the relevant analysis threshold. =0.18, repeat steps 2-5, and recalculate the magnetic charge density of each triangular facet. Total magnetic charge The magnetic anomaly components generated by the magnetic charge at each observation point, and the total magnetic anomaly value converted to the direction of the normal geomagnetic field, were superimposed, corrected, correlated, and stripped of residual data. The agreement was then verified again to achieve the desired result. =93% ( (≥90%), meeting the preset requirements.

[0095] 6.3 Contour maps (scalar + three components) and profile curves of magnetic anomalies before and after correction, and before and after residual stripping, were plotted to visually demonstrate the effect of eliminating topographic distortion. The final magnetic anomaly (scalar + three components) after residual stripping became continuous and its zonation was significantly enhanced, and the traces of topographic interference were basically eliminated, clearly reflecting the distribution characteristics of the underground target. Combined with geological drilling data, it was verified that the positioning error of the corrected magnetic anomaly data (scalar + three components) for the underground target was ≤ This meets the accuracy requirements for mineral resource exploration.

[0096] By comparison Figure 2 (Original aeromagnetic anomaly) Figure 9(Residual anomalies from the first geomagnetic modification) and Figure 11 (The remaining anomalies from the second geomagnetic correction) show that the violent fluctuations and local distortions caused by topographic undulations in the original anomalies are significantly eliminated after the two corrections of this invention. After the first correction, the main topographic anomalies have been suppressed, but some remain in certain areas. After the second correction, through correlation analysis and stripping of fitting residuals, the remaining anomalies become continuous and their banding is significantly enhanced. The traces of topographic interference are basically eliminated, and the distribution characteristics of underground targets can be clearly reflected, thus verifying the effectiveness of the method of this invention.

[0097] 6.4 Output the final terrain-corrected magnetic anomaly data (scalar) Final and three components final, final, Finally, the magnetic anomaly topographic correction treatment for the mountainous mining area was completed.

[0098] In this embodiment, the processing method of the present invention is used to concentrate the magnetic charge of the triangular facet to the midpoint, calculate the three components of the magnetic anomaly using Coulomb's law for point magnetic charge, and then combine it with the cosine of the normal geomagnetic field direction. , , ,Will , , Substituting into the total magnetic anomaly formula This significantly simplifies the calculation process and improves processing efficiency. Simultaneously, it adds correlation analysis and residual stripping steps, identifying residual topographic magnetic anomalies through correlation coefficients and stripping residual interference using quadratic polynomial fitting. This minimizes the impact of topographic magnetic anomalies, significantly enhancing the magneto-geochemical modification effect. It effectively eliminates magnetic anomaly distortion caused by mountainous terrain undulations and topographic magnetism, accurately restoring the true magnetic anomaly signal (scalar + three components) of the underground target body, providing reliable data support for subsequent mineral resource exploration and geological interpretation.

[0099] The embodiments described above are for illustrative purposes only and are not intended to limit the invention. Therefore, any changes in numerical values ​​or substitutions of equivalent elements should still fall within the scope of this invention.

[0100] The above detailed description will enable those skilled in the art to understand that the present invention can indeed achieve the aforementioned objectives and has complied with the provisions of the Patent Law.

[0101] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention. The above descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

[0102] It should be noted that the above description of the process is for illustrative purposes only and does not limit the scope of this specification. Those skilled in the art can make various modifications and changes to the process under the guidance of this specification. However, these modifications and changes remain within the scope of this specification.

[0103] The basic concepts have been described above. Obviously, for those skilled in the art who have read this application, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore, such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0104] Furthermore, this application uses specific terms to describe its embodiments. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different positions in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

Claims

1. A method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface, characterized in that, include: Step 1: Collect and preprocess magnetic exploration data, topographic elevation data, geological maps and stratigraphic magnetic statistics of the target work area to obtain the original scalar magnetic anomaly data, the original three-component magnetic anomaly data, the topographic elevation grid data including the outer extension area and the surface stratigraphic magnetic susceptibility distribution grid data for each observation point. Step 2: Based on the terrain elevation grid data, construct a terrain surface model composed of multiple triangular facets. Calculate the magnetic charge density and total magnetic charge of each triangular facet according to the surface stratum magnetic susceptibility distribution grid data and geomagnetic field environment parameters. Concentrate the total magnetic charge of each triangular facet to the midpoint of the triangular facet to form a point magnetic charge. All point magnetic charges constitute the terrain surface magnetic charge distribution model. Step 3: For each observation point, select all point magnetic charges within the influence range of the topographic surface magnetic charge according to the preset influence range of the topographic surface magnetic charge. Use the Coulomb law of point magnetic charge to calculate the contribution value of the three components of the magnetic anomaly generated by each point magnetic charge at the observation point. Add all the contribution values ​​to obtain the total value of the three components of the topographic surface magnetic charge magnetic anomaly at the observation point. Then convert the total value of the three components to the direction of the normal geomagnetic field to obtain the total magnetic anomaly value of the normal geomagnetic field direction at the observation point. Step 4: Overlay the total magnetic anomaly value of the normal geomagnetic field direction at each observation point with the original scalar magnetic anomaly data of that point to obtain the topographically corrected scalar magnetic anomaly data; at the same time, overlay the total value of the three components of the topographic surface magnetic charge magnetic anomaly at each observation point with the original three components of the magnetic anomaly data of that point to obtain the topographically corrected three components of the magnetic anomaly data. Step 5: Calculate the scalar correlation coefficient between the topographically corrected scalar magnetic anomaly data and the original scalar magnetic anomaly data for each observation point, and the component correlation coefficient between each component of the topographically corrected three-component magnetic anomaly data and the corresponding component of the original three-component magnetic anomaly data; identify the data components with residual topographic magnetic anomalies based on the preset correlation coefficient threshold, remove the residues from the data components with residuals using the fitting residual method, and obtain the final magnetic anomaly data of the component; for data components without residuals, directly use the topographically corrected data as the final magnetic anomaly data of the component. Step 6: Select known geological anomaly points within the target work area, and verify the consistency between the final magnetic anomaly data of each component and the known geological anomalies. If the consistency reaches the preset threshold, output the final topographically corrected magnetic anomaly data; otherwise, adjust the relevant calculation parameters and repeat steps 2 to 6.

2. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, In step 1: the magnetic exploration data includes the coordinates of each observation point, the scalar magnetic anomaly observation value, and the three-component magnetic anomaly observation values ​​in the x, y, and z directions; the topographic elevation data is obtained by UAV aerial survey or digital elevation model data, with the grid resolution set to 10 meters to 100 meters; the stratigraphic magnetic statistics are obtained by collecting rock samples from the surface strata in the target work area and conducting indoor magnetic susceptibility tests.

3. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, In step 2, when constructing the terrain surface model, a unit outward normal vector pointing towards the outside of the terrain is calculated for each triangular facet. When calculating the magnetic charge density of each triangular facet, the geomagnetic field direction vector is first determined based on the geomagnetic tilt and magnetic declination. The dot product of the geomagnetic field direction vector and the unit outward normal vector is calculated to obtain the cosine value of the included angle. Then, the geological magnetic susceptibility value of the area where the triangular facet is located, the average geomagnetic field value in the survey area, and the remanent magnetic induction ratio are obtained. The remanent magnetic induction ratio is added by 1 and then multiplied by the geological magnetic susceptibility value, the average geomagnetic field value, and the cosine value of the included angle.

4. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, The coordinates of the midpoint of the triangular facet in step 2 are determined by the average coordinates of the three vertices of the triangular facet; the total magnetic charge of the triangular facet is equal to the magnetic charge density of the triangular facet multiplied by the area of ​​the triangular facet.

5. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, In step 3, when using Coulomb's law to calculate the contribution of the three components of the magnetic anomaly generated by each point magnetic charge at the observation point, the required parameters include: vacuum permeability, the total magnetic charge of the point magnetic charge, the three components of the unit outward normal vector of the triangular facet containing the point magnetic charge, the spatial distance from the point magnetic charge to the observation point, the difference between the coordinates of the observation point and the coordinates of the midpoint of the point magnetic charge in each direction, and the dot product of the unit outward normal vector and the vector from the point magnetic charge to the observation point.

6. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, In step 3, when converting the total value of the three components of the topographic surface magnetic charge and magnetic anomaly to the total magnetic anomaly value in the direction of the normal geomagnetic field, the three direction cosines of the direction of the normal geomagnetic field are first determined according to the geomagnetic tilt and magnetic declination. Then, the three direction cosines are multiplied by the x, y, and z components in the total value of the three components of the topographic surface magnetic charge and magnetic anomaly, and then summed.

7. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, The calculation formulas for the scalar correlation coefficient and component correlation coefficient mentioned in step 5 are as follows: the sum of the products of the difference between the original magnetic anomaly data and its average value of all measuring points and the difference between the topographically corrected magnetic anomaly data and its average value of the corresponding measuring points, divided by the square root of the product of the sum of squares of the deviations of the original magnetic anomaly data and the sum of squares of the deviations of the topographically corrected magnetic anomaly data; the value range of the correlation coefficient threshold is 0.1 to 0.3, which is dynamically adjusted according to the topographic complexity of the target work area and the exploration accuracy requirements.

8. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, In step 5, when removing residual topographic magnetic anomalies from data components using the fitting residual method: if the correlation coefficient of the component is greater than or equal to 0.2, a quadratic polynomial nonlinear fitting model is preferred; if the correlation coefficient is less than 0.2, a linear fitting model is used; after the removal is completed, the correlation coefficient between the final magnetic anomaly data and the original magnetic anomaly data is recalculated. If the correlation coefficient of any component is still greater than or equal to the correlation coefficient threshold, the fitting model parameters are adjusted or a nonlinear fitting model is used to repeat the removal until the correlation coefficient of all components is less than the correlation coefficient threshold.

9. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, The preset matching threshold mentioned in step 6 is above 90%. While verifying the matching degree, a visual comparison is also made by drawing magnetic anomaly contour maps or profile curves before and after correction, and the positioning error of the final magnetic anomaly data on the underground target body is calculated in combination with geological drilling data to help evaluate the correction effect.

10. The method for correcting magnetic anomalies in terrain using the distribution of magnetic charge on the terrain surface according to claim 1, characterized in that, The range of influence of the topographic surface magnetic charge in step 3 is 30 to 50 kilometers, which is adjusted according to the complexity of the terrain and the exploration accuracy requirements of the target work area; the geomagnetic environment parameters in step 2 are obtained by on-site collection of geomagnetic observation instruments or by calculation using the international geomagnetic reference field model; the calculation, superposition and conversion of the three components of the magnetic anomaly contribution value of the point magnetic charge to the direction of normal geomagnetic field are performed in parallel.

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