A method for eliminating residual background magnetic field by using vertical first derivative and integral of magnetic anomaly

Abstract

The application provides a method for eliminating residual background magnetic field by using vertical first-order derivative and integral of magnetic anomaly, comprising the following steps: step one, obtaining measured magnetic field data of a magnetic exploration area; step two, data expansion processing; step three, performing fast Fourier forward transform processing on the expanded grid magnetic anomaly data; step four, performing vertical first-order derivative operation processing on the frequency domain magnetic anomaly spectrum data; step five, performing fast Fourier inverse transform processing on the frequency domain vertical first-order derivative spectrum data; step six, performing fast Fourier forward transform processing on the spatial domain vertical first-order derivative grid data; step seven, performing vertical integral operation processing on the frequency domain vertical first-order derivative second spectrum data; step eight, performing fast Fourier inverse transform processing on the frequency domain integral restored spectrum data; and step nine, region intercepting processing. The application is suitable for eliminating residual background magnetic field of high-precision magnetic anomaly data of diamond nitrogen vacancy color center magnetic measurement.

Description

Technical Field

[0001] This invention relates to the field of magnetic exploration (magnetic exploration) technology in geophysical exploration, and in particular to a method for eliminating residual background magnetic fields by using the vertical first derivative and integral of magnetic anomalies. Background Technology

[0002] Magnetic exploration, also known as magnetic exploration, is one of the important methods of geophysical exploration. Its core principle is to solve problems related to geological structure and mineral resource exploration by observing and analyzing the differences in magnetic fields of rocks or geological bodies within the Earth's crust.

[0003] Different rocks and minerals in the Earth's crust, due to variations in the content and structure of ferromagnetic minerals, generate different magnetic field characteristics, leading to deviations in the local geomagnetic field distribution from the normal geomagnetic field (i.e., magnetic anomalies). Magnetic exploration uses precise instruments to measure these magnetic anomalies and then combines this information with regional geological and drilling data to infer the location, morphology, and properties of underground magnetic geological bodies. Due to its high exploration efficiency, low cost, large detection depth, and wide range of information contained, magnetic exploration has been widely applied in many fields, including basic geological research, mineral resource exploration, engineering and environmental surveys, and marine geological investigations.

[0004] In magnetic exploration, the detection of magnetic anomalies in buried magnetic geological bodies or magnetic ore bodies (magnetite) begins with observing the Earth's magnetic field using a magnetometer. This observation is then processed according to the "High-Precision Magnetic Exploration Specifications." This processing corrects or eliminates anomalies caused by non-magnetic geological bodies, resulting in anomalies generated by magnetic geological bodies. Only observed magnetic anomalies obtained through this correction can be considered magnetic anomalies. It's important to note that, in a narrow sense, these anomalies caused by non-magnetic geological bodies are what is referred to as the magnetic background field. The magnetic background field is the benchmark geophysical field generated by the environmental medium surrounding the target object; it represents the normal field value or average disturbance level that highlights anomalies. The background field is the "benchmark," used to determine what constitutes an anomaly. Its core characteristic is a relatively stable, widely distributed magnetic field that remains constant within a certain spatial range. For a relatively small magnetic exploration area, the broader magnetic background field also includes magnetic anomalies generated by deep magnetic interfaces and large-scale magnetic bodies within the survey area. The Earth's magnetic field measured by conventional magnetometers and diamond nitrogen-vacancy color center magnetometers used in modern magnetic exploration is the absolute value of the geomagnetic field. The geomagnetic field observed at the measuring point is called the measured field value at the measuring point. By correcting the measured field value at the measuring point using: measured field value at the measuring point - normal field - diurnal variation correction - other correction terms, the magnetic anomaly used by magnetic exploration to detect magnetic geological bodies and conduct geological interpretation is obtained.

[0005] In the correction of measured magnetic anomalies, there is a diurnal variation correction, the magnitude of which determines a magnetic field value called the diurnal variation station base value. ). Regarding this The selection of the magnitude is clearly defined in the magnetic measurement specifications. The basic method is to select a region with a gradual change within a normal 24-hour diurnal variation observation period and average the observed magnetic field as the mean. The more detailed process of obtaining this information will not be described here. However, even following the standards, it is difficult to select the most reliable location of the non-magnetic anomaly to obtain the optimal result. The presence of underground magnetic bodies at the location of the diurnal variation station, causing magnetic anomalies, has influenced the magnetic field to some extent. The accuracy of the result. The accuracy of the data directly affects the size of the positive and negative magnetic anomaly regions and the amplitude variations of the anomalies in the survey area. According to magnetic survey specifications, it is difficult to guarantee that there are no geological bodies at the location of the diurnal variation station that could cause magnetic anomalies, thus making it difficult to interpret the results obtained from the diurnal variation station according to the specifications. This refers to the optimal base value for obtaining daily variables. When based on the values ​​obtained from the daily variable station... When the base value is higher than the accurate diurnal variation correction baseline, the area of ​​positive magnetic anomaly after diurnal variation correction in the survey area increases, and the amplitude of the positive magnetic anomaly increases. Conversely, the area of ​​negative magnetic anomaly in the survey area will increase, and the amplitude of the negative magnetic anomaly will also increase. The inaccuracy caused by inaccurate selection of the base value of the diurnal variation station for magnetic diurnal variation correction is a constant step change. This inaccurate constant value either raises or lowers the magnetic anomaly in the survey area. The overall shift of the base value will only cause the calculated magnetic anomaly to rise or fall by a fixed difference, without changing the gradient, shape, or relative amplitude of the anomaly. However, it will affect the changes in the positive and negative areas and the amplitudes of the positive and negative magnetic anomalies in the survey area. We will temporarily denote the deviation of the base value controlling the diurnal variation correction from the accurate base value as _____. .

[0006] In the correction of measured magnetic anomalies, there is also a normal field correction. This correction typically uses the geomagnetic normal field calculated from the International Geomagnetic Reference Field (IGRF), a global standard model of the geomagnetic field updated every five years by the International Association for Geomagnetism and Upper Atmosphere (IAGA), to correct the measured magnetic field in the survey area. Based on the coordinates of the measuring point, the normal field of the measuring point can be calculated according to the IGRF model, and the measured magnetic field can be corrected accordingly. However, there is a certain difference between the normal field calculated according to the IGRF magnetic model and the "normal field" of the magnetic survey area. This difference is extremely gradual within the magnetic survey area; we define this difference, which varies with the planar position of the measuring point, as... In principle, this difference will not have a significant impact on the morphology and gradient of the magnetic anomaly. However, it will affect the range of the positive and negative regions of the magnetic anomaly in the survey area and the magnitude of the positive and negative values ​​of the anomaly. This effect is not mentioned in the existing magnetic survey specifications and is a potential influence on local magnetic anomalies.

[0007] Furthermore, in small-area magnetic exploration for metallic mineral deposits, magnetic anomalies generated by large-scale deep geological bodies or magnetic interfaces, as well as continental magnetic anomalies resulting from mantle convection, are also among the causes of small-area magnetic anomalies. These magnetic anomalies are an important component of the background field relative to the small-area magnetic anomalies. Such magnetic anomalies are also characterized by their gentle slope and, in small-area magnetic exploration, can be considered to be largely independent of altitude. They can also be interpreted as the coordinates of the measuring points (…). We consider this unremoved anomaly, a function of , as a factor requiring magnetic anomaly background correction. We call this anomaly a regional magnetic anomaly, denoted as . .

[0008] Depend on , The combined effect of these three factors causes the positive and negative regions and amplitudes of the magnetic anomalies in the survey area to deviate from the true nature of the magnetic anomalies. Although this difference does not significantly alter the morphology or amplitude of the magnetic anomalies, it has a major impact on geological interpretation using magnetic anomalies. It directly affects the qualitative and quantitative interpretations of magnetic anomalies, as well as the results of two-dimensional and three-dimensional inversions, and can directly lead to systematic errors in the magnetization intensity and magnetic body occurrence of the inversion results.

[0009] Daily variable station base value The selection of [a specific parameter] indirectly affects the background of magnetic anomalies in the survey area through diurnal variation corrections. Similarly, the use of the International Geomagnetic Reference Field (IGRF) model for measured magnetic surveys in the survey area has also helped to eliminate the background. As analyzed earlier, due to [the specific factor]... The inaccurate selection of the field and the fact that the normal field calculated using the IGRF magnetic model may not be the optimal normal field background for the survey area both contribute to the deviations. and Together, these factors contribute to an incompletely corrected background bias in the magnetic anomaly data of the survey area. This bias significantly affects the positive and negative regions of the magnetic anomaly, as well as the amplitudes of both positive and negative anomalies, and may even determine whether a negative anomaly exists locally. Of course, even if a negative magnetic anomaly exists, this bias can alter the amplitude of a positive anomaly, significantly impacting our understanding of its geological origins.

[0010] Magnetic anomalies produced by single magnetic geological bodies can be roughly divided into the following three categories, and each category of magnetic anomalies is closely related to the extension of the magnetic geological body.

[0011] The first type is localized magnetic anomalies with no negative magnetic anomalies. These anomalies typically represent magnetic anomalies produced by an infinitely extending magnetic body with parasitic magnetization. The second type is localized magnetic anomalies with negative magnetic anomalies on one side. These anomalies typically represent magnetic anomalies produced by a surface of an infinitely extending magnetic body with its magnetization vector obliquely intersecting the surface.

[0012] The third type is local magnetic anomalies with negative magnetic anomalies on both sides. These magnetic anomalies usually represent the magnetic anomalies of finite-length magnetic bodies.

[0013] Given the crucial importance of the presence and form of positive and negative magnetic anomalies for understanding magnetic geological bodies, further corrections should be made to magnetic anomalies that have already undergone diurnal and normal field corrections. (Correction due to...) Error caused by inaccuracy Differences in the normal field caused by inaccurate correction to the normal field and due to deep factors In order to restore the true nature of the actual magnetic anomaly in the magnetic survey area.

[0014] The presence of negative magnetic anomalies in a local magnetic field, to a certain extent, determines the extent of the extension of the magnetic geological body that produces the anomaly. The magnitude of the background field of the magnetic anomaly plays a crucial controlling role in determining whether a negative magnetic anomaly exists. Therefore, determining the magnitude of the background magnetic anomaly in a magnetic survey area is a critical scientific issue, especially when further background field correction is performed on magnetic anomalies that have already undergone background field correction.

[0015] There is currently no known method for background field correction of a magnetic measurement area. Summary of the Invention

[0016] This invention provides a method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies, and for correcting the background of magnetic anomalies in the survey area. This fills a gap in processing methods in this field, and is particularly suitable for eliminating residual background magnetic fields in high-precision magnetic anomaly data from diamond nitrogen-vacancy color center magnetic measurements. It provides an effective and accurate method for correcting residual background magnetic fields, enabling the magnetic anomalies in the survey area to more accurately reflect the magnetic anomaly characteristics of magnetic geological bodies. This provides an effective processing means to improve the reliability of magnetic anomaly geological interpretation and to obtain magnetic anomalies without the influence of background magnetic fields by accurately inverting ore-forming geological bodies using magnetic anomalies.

[0017] To achieve the above objectives, the present invention adopts the following technical solution: A method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies includes: Step 1: Obtain the measured magnetic field data of the magnetic exploration area, and perform conventional correction and curvature leveling on the measured magnetic field data to obtain regular grid magnetic anomaly data on a unified elevation plane that includes the target magnetic anomaly and the residual background magnetic field. Step 2: Perform data augmentation on the regular grid magnetic anomaly data to obtain augmented grid magnetic anomaly data that meets the requirements of Fast Fourier Transform. Step 3: Perform Fast Fourier Transform on the expanded grid magnetic anomaly data to obtain frequency domain magnetic anomaly spectrum data; Step 4: Based on the physical characteristic that the residual background magnetic field is independent of the observation elevation, the vertical first derivative operation is performed on the frequency domain magnetic anomaly spectrum data to remove the spectral components corresponding to the residual background magnetic field, and obtain frequency domain vertical first derivative spectrum data containing only the target magnetic anomaly information. Step 5: Perform inverse fast Fourier transform on the frequency domain vertical first derivative spectrum data to obtain spatial domain vertical first derivative grid data. Step 6: Perform Fast Fourier Transform on the spatial domain vertical first derivative grid data to obtain the frequency domain vertical first derivative quadratic spectrum data. Step 7: Perform vertical integration on the frequency domain vertical first derivative quadratic spectrum data to reconstruct the target magnetic anomaly and obtain frequency domain integrated reconstructed spectrum data. Step 8: Perform fast inverse Fourier transform on the frequency domain integral restored spectrum data to obtain the expanded region background-removed magnetic anomaly grid data. Step 9: According to the grid range of the test area corresponding to the regular grid magnetic anomaly data, perform regional truncation processing on the background-removed magnetic anomaly grid data of the expanded area to obtain the target magnetic anomaly data of the test area after eliminating the residual background magnetic field.

[0018] In this specification, the residual background magnetic field refers to the magnetic field component remaining after the measured magnetic field data has undergone the conventional correction, which is independent of the observation elevation and only varies with the plane position. It includes at least one of the following: the daily variation correction base value deviation component caused by the base value selection deviation in the daily variation correction, the normal field calculation deviation component caused by the calculation deviation of the International Geomagnetic Reference Field Model, and the regional magnetic anomaly component caused by deep geological bodies.

[0019] In this specification, in step one, the curvature-leveling process involves converting measured magnetic field data at different observation elevations into a uniform horizontal elevation plane through magnetic anomaly potential field curvature-leveling transformation, so as to obtain regular grid magnetic anomaly data on that horizontal elevation plane.

[0020] In this specification, in step two, the data augmentation process uses a cosine window function to symmetrically augment the regular grid magnetic anomaly data on all four sides. The number of survey lines and the number of measurement points on a single survey line in the augmented grid magnetic anomaly data are both integer powers of 2.

[0021] In this specification, step four, the vertical first derivative operation processing, is based on the magnetic anomaly potential field frequency domain conversion rule. The frequency domain magnetic anomaly spectrum data is processed by performing the frequency response operation of the vertical first derivative, and the spectral components corresponding to the residual background magnetic field that are independent of the elevation are removed to obtain the frequency domain vertical first derivative spectrum data containing only the target magnetic anomaly information.

[0022] In this specification, the frequency domain vertical first derivative spectrum data obtained in step four retains only the vertical variation spectrum component corresponding to the target magnetic anomaly, and completely removes the zero vertical variation spectrum component corresponding to the residual background magnetic field.

[0023] In this specification, step seven, the vertical integration operation, is based on the frequency domain conversion rule of the magnetic anomaly potential field. It involves performing a frequency response operation on the frequency domain vertical first derivative quadratic spectrum data to restore the frequency domain integrated restored spectrum data corresponding to the target magnetic anomaly.

[0024] In this specification, during step four, the zero-frequency component in the frequency domain magnetic anomaly spectrum data is set to zero during the vertical first derivative operation; and during step seven, the zero-frequency component in the frequency domain vertical first derivative second spectrum data is set to zero during the vertical integral operation.

[0025] In this specification, the measured magnetic field data comes from diamond nitrogen vacancy color center magnetic measurements. In step one, the routine calibration also includes probe attitude correction and temperature drift correction.

[0026] In this specification, after step nine, the following is also included: The regular grid magnetic anomaly data obtained in step one is compared with the target magnetic anomaly data obtained in step nine to obtain the residual background magnetic field data of the survey area. The residual background magnetic field data is then used for background field feature analysis in the geological interpretation of magnetic anomalies.

[0027] In summary, the present invention has at least the following beneficial effects: This invention can accurately and efficiently eliminate residual background magnetic fields unrelated to elevation in magnetic anomaly data. It can completely remove linear trend residual background fields, restore the true magnetic anomaly characteristics of the target magnetic body, and solve the core industry problem that conventional correction processes cannot completely eliminate background field residuals. The method of this invention is standardized, has high computational efficiency, and is highly adaptable. It can be widely used in conventional data processing of airborne magnetic exploration and ground magnetic exploration, and is especially suitable for processing high-precision magnetic data such as diamond nitrogen vacancy color center magnetic measurement. This invention significantly improves the accuracy and reliability of magnetic anomaly data, effectively avoids misjudgment of magnetic body characteristics caused by background field residuals, greatly improves the accuracy of qualitative and quantitative interpretation of magnetic anomalies and two-dimensional and three-dimensional inversion results, and provides reliable data support for the geological application of magnetic exploration. This invention fills the technical gap in the industry regarding targeted correction methods for residual background magnetic fields of magnetic anomalies, improves the data processing flow of magnetic exploration, and provides core technical support for the in-depth application of high-precision magnetic surveying technology. Attached Figure Description

[0028] 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.

[0029] Figure 1 This is a schematic diagram of the method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies involved in this invention.

[0030] Figure 2 This is a schematic diagram of the single-model magnetic anomaly, the simulated linear background magnetic field residual, and the synthesis of the two involved in this invention.

[0031] Figure 3 This is a schematic diagram of the single-model magnetic anomaly, the background magnetic field residual of the simulated quadratic polynomial, and their synthesis involved in this invention.

[0032] Figure 4 This is a schematic diagram of the multi-model magnetic anomaly, the simulated linear background magnetic field residual, and the synthesis of the two involved in this invention.

[0033] Figure 5 This is a schematic diagram of the multi-model magnetic anomaly, the background magnetic field residual of the simulated quadratic polynomial, and the synthesis of the two involved in this invention.

[0034] Figure 6 for Figure 2 A schematic diagram of the process and results of extracting the residual of the model's background magnetic field.

[0035] Figure 7 for Figure 3 A schematic diagram of the process and results of extracting the residual of the model's background magnetic field.

[0036] Figure 8 for Figure 4 A schematic diagram of the process and results of extracting the residual of the model's background magnetic field.

[0037] Figure 9 for Figure 5 A schematic diagram of the process and results of extracting the residual of the model's background magnetic field.

[0038] Figure 10 A schematic diagram of the process of eliminating background magnetic field residuals and the magnetic anomaly processing for eliminating background magnetic field residuals in the GLL region.

[0039] Figure 11 This is a schematic diagram of the magnetic anomaly plane contour map before and after removing the background magnetic field residual in the GLL region.

[0040] Figure 12 for Figure 11 A schematic diagram comparing the magnetic anomaly in the GLL region with the magnetic anomaly after eliminating the background magnetic field residual. Detailed Implementation

[0041] 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.

[0042] 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.

[0043] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0044] like Figure 1 As shown, a method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies includes: Step 1: Obtain the measured magnetic field data of the magnetic exploration area, and perform conventional correction and curvature leveling on the measured magnetic field data to obtain regular grid magnetic anomaly data on a unified elevation plane that includes the target magnetic anomaly and the residual background magnetic field. Step 2: Perform data augmentation on the regular grid magnetic anomaly data to obtain augmented grid magnetic anomaly data that meets the requirements of Fast Fourier Transform. Step 3: Perform Fast Fourier Transform on the expanded grid magnetic anomaly data to obtain frequency domain magnetic anomaly spectrum data; Step 4: Based on the physical characteristic that the residual background magnetic field is independent of the observation elevation, the vertical first derivative operation is performed on the frequency domain magnetic anomaly spectrum data to remove the spectral components corresponding to the residual background magnetic field, and obtain frequency domain vertical first derivative spectrum data containing only the target magnetic anomaly information. Step 5: Perform inverse fast Fourier transform on the frequency domain vertical first derivative spectrum data to obtain spatial domain vertical first derivative grid data. Step 6: Perform Fast Fourier Transform on the spatial domain vertical first derivative grid data to obtain the frequency domain vertical first derivative quadratic spectrum data. Step 7: Perform vertical integration on the frequency domain vertical first derivative quadratic spectrum data to reconstruct the target magnetic anomaly and obtain frequency domain integrated reconstructed spectrum data. Step 8: Perform fast inverse Fourier transform on the frequency domain integral restored spectrum data to obtain the expanded region background-removed magnetic anomaly grid data. Step 9: According to the grid range of the test area corresponding to the regular grid magnetic anomaly data, perform regional truncation processing on the background-removed magnetic anomaly grid data of the expanded area to obtain the target magnetic anomaly data of the test area after eliminating the residual background magnetic field.

[0045] In some embodiments, the residual background magnetic field is the magnetic field component remaining after the measured magnetic field data has been conventionally corrected, which is independent of the observation elevation and only varies with the plane position, including at least one of the following: the daily variation correction base value deviation component caused by the base value selection deviation in the daily variation correction, the normal field calculation deviation component caused by the calculation deviation of the International Geomagnetic Reference Field Model, and the regional magnetic anomaly component caused by deep geological bodies.

[0046] In some embodiments, in step one, the curvature-leveling process involves converting measured magnetic field data at different observation elevations into magnetic anomaly potential field curvature-leveling data, and uniformly reducing them to the same horizontal elevation plane to obtain regular grid magnetic anomaly data on that horizontal elevation plane.

[0047] In some embodiments, in step two, the data augmentation process uses a cosine window function to symmetrically augment the regular grid magnetic anomaly data on all four sides. The number of survey lines and the number of measurement points on a single survey line in the augmented grid magnetic anomaly data are both integer powers of 2.

[0048] In some embodiments, in step four, the vertical first derivative operation is performed based on the magnetic anomaly potential field frequency domain conversion rule. The frequency response operation of the vertical first derivative is performed on the frequency domain magnetic anomaly spectrum data, and the spectral components corresponding to the residual background magnetic field that are independent of elevation are removed to obtain the frequency domain vertical first derivative spectrum data containing only the target magnetic anomaly information.

[0049] In some embodiments, the frequency domain vertical first derivative spectrum data obtained in step four retains only the vertical variation spectrum component corresponding to the target magnetic anomaly, and completely removes the zero vertical variation spectrum component corresponding to the residual background magnetic field.

[0050] In some embodiments, in step seven, the vertical integration operation is based on the frequency domain conversion rule of the magnetic anomaly potential field. The frequency response operation of the second-order vertical derivative of the frequency domain is performed on the frequency domain vertical first derivative, and the frequency domain integrated restored spectrum data corresponding to the target magnetic anomaly is obtained.

[0051] In some embodiments, during step four, the zero-frequency component in the frequency domain magnetic anomaly spectrum data is set to zero during the vertical first derivative operation; and during step seven, the zero-frequency component in the frequency domain vertical first derivative second spectrum data is set to zero during the vertical integration operation.

[0052] In some embodiments, the measured magnetic field data is derived from diamond nitrogen vacancy color center magnetometry. In step one, the conventional calibration also includes probe attitude correction and temperature drift correction.

[0053] In some embodiments, after step nine, the method further includes: The regular grid magnetic anomaly data obtained in step one is compared with the target magnetic anomaly data obtained in step nine to obtain the residual background magnetic field data of the survey area. The residual background magnetic field data is then used for background field feature analysis in the geological interpretation of magnetic anomalies.

[0054] In some embodiments, in step one, if the measured magnetic field data obtained after conventional correction and curvature flattening is irregular grid data, then the irregular grid data is first subjected to interpolation and regrinding processing to obtain the regular grid magnetic anomaly data in the form of a rectangular grid with equal point and line spacing.

[0055] In some embodiments, the interpolation regrinding process employs Kriging interpolation or bilinear interpolation, and the point spacing and line spacing of the generated regular grid magnetic anomaly data are equal, with each grid node corresponding one-to-one with the planar coordinates of the measured points in the survey area.

[0056] In some embodiments, when the point-to-line spacing of the regular grid magnetic anomaly data is equal, and the number of survey lines and the number of survey points per survey line are values ​​other than the smallest power of 2 greater than the corresponding number of the original regular grid, the number of survey lines and the number of survey points per survey line of the expanded grid magnetic anomaly data after the data expansion processing in step two are both powers of 2.

[0057] In some embodiments, in step three, the fast Fourier transform processing is to perform a two-dimensional fast Fourier transform on the expanded grid magnetic anomaly data, and a cosine window function is used for spectral smoothing during the transformation process to suppress spectral leakage.

[0058] In some embodiments, in step four, the vertical first derivative operation process uses the magnetic anomaly potential field vertical derivative operator H(ω)=ω, which matches the radial frequency, to perform point-by-point multiplication operations on the frequency domain magnetic anomaly spectrum data.

[0059] In some embodiments, in step seven, the vertical integration operation uses the magnetic anomaly potential field vertical integration operator H(ω)=1 / ω, which is matched with the radial frequency, to perform point-by-point multiplication operations on the second spectrum data of the vertical first derivative in the frequency domain.

[0060] In some embodiments, the zero-frequency component is set to zero in the vertical first derivative operation and / or the vertical integration operation.

[0061] In some embodiments, in step six, the fast Fourier transform processing uses the same two-dimensional fast Fourier transform parameters as in step three to transform the spatial domain vertical first derivative grid data, thereby obtaining the frequency domain vertical first derivative second spectrum data that perfectly matches the dimension of the frequency domain magnetic anomaly spectrum data.

[0062] In some embodiments, before performing region truncation processing on the background magnetic anomaly grid data of the expanded region in step nine, the edge grid data of the expanded region is first truncated to remove edge distortion data caused by Fourier transform, and then the region truncation processing is performed.

[0063] In some embodiments, the method is applied to the processing of magnetic anomaly data from airborne magnetic exploration, ground magnetic exploration, or diamond nitrogen-vacancy color center magnetic measurements, to eliminate residual background magnetic fields that cannot be completely corrected by conventional correction procedures.

[0064] The technical concept of this invention is as follows: Based on magnetic potential field theory, this invention utilizes the inherent physical property that the vertical first derivative of the residual background magnetic field, which is independent of elevation, is always 0, to construct the core processing logic of "stripping the background field with the vertical first derivative and restoring the target magnetic anomaly with the vertical integral". All operations are implemented in the frequency domain based on Fast Fourier Transform (FFT).

[0065] The core standardized process of the scheme is as follows: First, the magnetic anomaly grid data, which has been conventionally corrected and leveled to the same elevation plane, is symmetrically expanded using a cosine window function to meet the requirements of FFT operation. Then, the expanded data is subjected to FFT forward transformation to convert the spatial domain magnetic anomaly into the frequency domain spectrum. The vertical first derivative operation is performed in the frequency domain to completely remove the influence of the residual background field. Then, the spectrum of the target magnetic anomaly is restored by vertical integration operation. Finally, the data is converted back to the spatial domain by FFT inverse transformation, and the effective data of the original survey area is extracted to obtain the target magnetic anomaly after eliminating the residual background magnetic field.

[0066] 1. The mathematical and physical principle of eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies: As explained in the background section of this invention, the background anomaly of a magnetic anomaly has a very flat magnetic field that does not change significantly with altitude. Therefore, the altitude range of the magnetic observation point can be considered as a planar position only. The residual of the background magnetic field that cannot be completely eliminated is also a function of the planar position. Therefore, the residual of the background magnetic field that cannot be eliminated in the magnetic anomaly is defined as a function independent of elevation and only dependent on the planar position. According to the description of the background art of the present invention, it is obvious .

[0067] The measured magnetic field value, after undergoing various corrections according to the magnetic exploration specifications, represents the spatial location of the magnetic anomaly. The function can define a magnetic anomaly that has been corrected according to specifications as... Magnetic anomalies generated by magnetic bodies in underground spaces are also a spatial location. The function of this magnetic anomaly is the target magnetic anomaly used for qualitative and quantitative interpretation of magnetic geological bodies using magnetic anomalies, and this magnetic anomaly is defined as... Without a doubt, and and The three have the following relationship: (1) because It is a function independent of elevation; when its vertical first derivative is calculated, its vertical first derivative is zero. .

[0068] After taking the vertical first derivative with respect to both sides of equation (1), we get: (2) By adjusting both sides of equation (2) By integrating, we can obtain: (3) if It is an abstract function, so for both sides of equation (2) After integration, there must exist a parallel with... Unrelated bivariate functions However, for actual magnetic anomalies It is a single-valued function with a known value, and after the numerical differentiation calculation of equation (2), it is implicitly related only to the coordinate position. The derivative of the relevant part of the value is zero. Conversely, through numerical integration of equation (3) That is, it equals 0, that is, equation (3) actually becomes: ; Magnetic anomaly containing background residuals after observation and correction according to magnetic measurement specifications. The result obtained after combining equations (2) and (3) that is Target magnetic anomaly for eliminating background magnetic field residuals This achieves the goal of accurately obtaining the magnetic anomalies generated by underground magnetic bodies.

[0069] According to the combined analysis of equations (2) and (3) on magnetic anomalies The processing is performed in the frequency domain. Magnetic anomaly processing in the frequency domain is based on flattening the magnetic anomaly curve to a certain value. The planar magnetic anomaly. Therefore, the vertical first derivative obtained according to equations (2) and (3) and the residual after removing the background magnetic field. That is Vertical first derivative of magnetic anomaly on a plane and Target magnetic anomaly on a plane.

[0070] Based on the above mathematical and physical principles combined with the magnetic anomaly potential field theory, The processing obtained This achieves the goal of eliminating background magnetic field residuals.

[0071] 2. Calculation steps for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies: Whether it's airborne magnetic exploration, surface magnetic exploration, or diamond nitrogen vacancy color center magnetic measurement, it always involves flattening the measured magnetic field to a certain degree. Only by establishing a high-altitude plane can other data processing of magnetic anomalies be performed. Assuming the measured magnetic field has undergone various corrections and is flattened to a certain height... The magnetic anomaly of the plane is The following processing of the residual magnetic field for background magnetic anomaly removal is based on... To be processed.

[0072] First, assume that the magnetic exploration area is a rectangle with equal spacing between exploration points and lines. There are a total of There are 3 survey lines, and each survey line has 100 survey lines. There are 10 measurement points. Other rectangular meshes with unequal point-to-line spacing can be converted into rectangular meshes with equal point-to-line spacing through interpolation or re-meshing.

[0073] The following is based on The grid magnetic anomaly was analyzed in the frequency domain using a Fast Fourier Transform (FFT). The process involves removing the background magnetic field residuals. For ease of description, the steps are as follows: Write as discrete The form is: where i = 1, 2, 3, ..., m; j = 1, 2, 3, ..., n; i and j are custom line point numbers for the magnetic measuring points, and are abbreviated as . FFT() represents the forward Fourier transform. -1 ( ) represents the inverse Fourier transform; represent Fourier spectrum after data expansion and satisfying FFT() transform; These are the frequencies along the measurement point direction and along the measurement line direction in the frequency domain, respectively; let... , The radial frequency is in the two-dimensional frequency domain.

[0074] (1) Expanding data to : Using the cosine window function to Expanding to 0 points around the perimeter, the survey lines consist of m² lines, with n² points on each line. , and record as The outer perimeter of the survey network should be symmetrical. (The last sentence appears to be incomplete and possibly contains errors.) , ,but , ; Indicates the rounding operation. Represents the natural logarithm operation.

[0075] (2) Calculation : right T( Perform a Fast Fourier Transform on the data to convert the data into a Fast Fourier Transform. Transform T(m2, n2) into the frequency domain to obtain... T( ) spectrum ,Right now =FFT( T( )).

[0076] (3) T( Calculation of the vertical first derivative of : ① Seek T( The spectrum of the vertical first derivative of ) For calculation The vertical first derivative needs to be calculated first. T( The vertical first derivative of ). According to magnetic exploration theory, it is calculated in the frequency domain. T( The vertical first derivative of ) needs to be calculated first. T( The spectrum of the vertical first derivative, that is, the frequency response using the vertical first derivative. ride That is, obtained T( The spectrum of the vertical first derivative of ), i.e. , for T( The spectrum of the vertical first derivative of ).

[0077] ② T( Calculation of the vertical first derivative of : According to the principle of Fourier transform, By performing an inverse Fourier transform, we can obtain T( The vertical first derivative of ), i.e. .

[0078] (4) ( Calculation of vertical integrals: ① Seek T( The spectrum of the vertical first derivative-integral: In order to obtain T( The spectrum of the vertical first derivative-integral of ). According to the magnetic exploration theory, first calculate , and then Frequency response multiplied by the integral That is , for T( The spectrum obtained by integrating the vertical first derivative of () is obtained by integrating.

[0079] It is important to emphasize here. ≠ .

[0080] ② Find T( The integral after the vertical first derivative of ) ( ): According to the principle of Fourier transform, By performing an inverse Fourier transform, we can obtain ( ),Right now .

[0081] (5) Determine the magnetic anomaly in the survey area Magnetic anomaly after eliminating residual background magnetic field: In fact, it is obtained through step (4). This refers to the magnetic anomaly within the expanded region after eliminating the residual background magnetic field. Simply follow... The grid area from The area was restored The corresponding grid range The data grid completed the magnetic anomaly of the survey area. Magnetic anomaly after eliminating residual background magnetic field, i.e. = .

[0082] The five steps (1)-(5) above constitute the mathematical method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies in this invention, along with detailed data processing. Following these five steps, the influence of background field residuals can be removed from the magnetic anomalies, accurately restoring the original characteristics of the local geological magnetic anomalies in the survey area. This effectively enhances the reliability of magnetic anomalies in solving geological problems and improves the geological application effects of qualitative and quantitative interpretations of magnetic anomalies and two-dimensional and three-dimensional inversions of magnetic anomalies. This elimination of actual magnetic anomaly background magnetic field residuals and enhancement of magnetic anomaly reliability is the core idea of ​​this invention.

[0083] The calculation results of the residual magnetic field of the background magnetic anomaly model of this invention: 1. Single-model magnetic anomaly and simulated linear background magnetic field residuals, and their synthesis: refer to Figure 2 , Figure 2This diagram illustrates the combination of a single-model magnetic anomaly, the simulated linear background magnetic field residual, and the synthesis of the two. In the diagram, A represents the single-model magnetic anomaly, B represents the simulated linear background magnetic field residual, and C represents the synthesis of the magnetic anomaly and the background magnetic field residual.

[0084] To more intuitively utilize the application effect of the present invention in eliminating background magnetic field residuals, a single model best demonstrates the capabilities of the patented method. Therefore, the magnetic anomaly of a finite-length, perpendicularly magnetized prism was forward modeled ( Figure 2 (A) and the residual background magnetic field with a linear trend of zero vertical first derivative ( Figure 2 (B in the text) and the magnetic anomaly resulting from the combination of the two ( Figure 2 (C in the middle).

[0085] 2. Single-model magnetic anomaly and simulated quadratic polynomial background magnetic field residuals and their synthesis: refer to Figure 3 , Figure 3 This diagram illustrates the magnetic anomaly of a single model, the background magnetic field residual of the simulated quadratic polynomial, and their synthesis. In the diagram, A represents the magnetic anomaly of the single model, B represents the background magnetic field residual of the simulated quadratic polynomial, and C represents the synthesis of the magnetic anomaly and the background magnetic field residual.

[0086] Based on the magnetic anomaly of the single model ( Figure 3 A) in the middle is superimposed with a quadratic polynomial background magnetic field residual ( Figure 3 Magnetic anomaly in B) Figure 3 (C in the text). Although the residual of this quadratic polynomial background magnetic field is also a residual of a regional background magnetic field, the anomaly also has the characteristics of a geological magnetic anomaly to a certain extent. Therefore, the residual of this background magnetic anomaly does not have the characteristic that the vertical first derivative is zero.

[0087] 3. Multi-model magnetic anomalies and simulated linear background magnetic field residuals, and their synthesis: refer to Figure 4 , Figure 4 This is a schematic diagram of the multi-model magnetic anomaly, the simulated linear background magnetic field residual, and their synthesis. In the diagram, A represents the multi-model magnetic anomaly, B represents the simulated linear background magnetic field residual, and C represents the synthesis of the magnetic anomaly and the background magnetic field residual.

[0088] To simulate more objective and realistic magnetic anomalies, multiple magnetic anomaly models with different magnetization directions and intensities were designed. Figure 4 (A) and superimposed with a linear trend of zero vertical first derivative background magnetic field residual ( Figure 4 (B in the text) and the magnetic anomaly resulting from the combination of the two ( Figure 4 (C in the middle).

[0089] 4. Multi-model magnetic anomalies and simulated quadratic polynomial background magnetic field residuals and their synthesis: refer to Figure 5 , Figure 5 A schematic diagram of the multi-model magnetic anomaly, the simulated quadratic polynomial background magnetic field residual, and their synthesis. In the diagram, A represents the multi-model magnetic anomaly, B represents the simulated quadratic polynomial background magnetic field residual, and C represents the synthesis of the magnetic anomaly and the background magnetic field residual.

[0090] To simulate more objective and realistic magnetic anomalies, multiple magnetic anomaly models with different magnetization directions and intensities were designed. Figure 5 (A) and superimposed a quadratic polynomial background magnetic field residual ( Figure 5 Magnetic anomaly in B) Figure 5 (C in the text). Although the residual of this quadratic polynomial background magnetic field is also a residual of a regional background magnetic field, the anomaly also has the characteristics of a geological magnetic anomaly to a certain extent. Therefore, the residual of this background magnetic anomaly does not have the characteristic that the vertical first derivative is zero.

[0091] 5. Calculation results of single-model simulation of magnetic anomaly and background magnetic field residuals using linear background magnetic field residuals: refer to Figure 6 , Figure 6 for Figure 2 A schematic diagram of the process and results of extracting the residual of the model background magnetic field, where A: the combined magnetic anomaly of the single model magnetic anomaly and the linear background magnetic field residual; B: the vertical first derivative of the magnetic anomaly represented by Figure A; C: the magnetic anomaly after removing the residual of the background magnetic field; and D: the obtained linear background magnetic field residual.

[0092] Using this method to Figure 2 The magnetic anomaly shown in Figure C underwent processing to eliminate the magnetic background field residual, resulting in the final magnetic anomaly after eliminating the background magnetic field residual. Figure 6 C in the equation and the residual of the eliminated background magnetic field ( Figure 6 (D) Because the linear background magnetic field residual fully meets the elimination conditions of the method of this invention, the obtained background magnetic anomaly residual and magnetic anomaly are completely consistent with the model. Eliminating the background magnetic field residual from the magnetic anomaly has achieved a very satisfactory result.

[0093] 6. Calculation results of single-model simulation of magnetic anomaly and background magnetic field residuals using quadratic polynomial background magnetic field residuals: refer to Figure 7 , Figure 7 for Figure 3A schematic diagram of the process and results of extracting the residual of the background magnetic field of the model, wherein A: the combined magnetic anomaly of the single model magnetic anomaly and the residual of the quadratic polynomial background magnetic field, B: the vertical first derivative of the magnetic anomaly, C: the magnetic anomaly after removing the residual of the background magnetic field, and D: the obtained residual of the background magnetic field.

[0094] Using the method of the present invention to Figure 3 The magnetic anomaly shown in Figure C underwent processing to eliminate the magnetic background field residual, resulting in the final magnetic anomaly after eliminating the background magnetic field residual. Figure 7 C in the equation and the residual of the eliminated background magnetic field ( Figure 7 (D in the original text). Because the residual of the quadratic polynomial background magnetic field does not completely satisfy the elimination conditions of the method of the present invention, the obtained residual of the background magnetic anomaly and the magnetic anomaly are somewhat different from the model. This is mainly because the residual of the simulated quadratic polynomial background magnetic field still has the anomalous characteristics of the magnetic body, and its vertical first derivative is not completely zero.

[0095] 7. Calculation results of multi-model simulation of magnetic anomalies and background magnetic field residuals using linear background magnetic field residuals: refer to Figure 8 , Figure 8 for Figure 4 A schematic diagram of the process and results of extracting the residual of the model background magnetic field, where A: the combined magnetic anomaly of the multi-model magnetic anomaly and the linear background magnetic field residual, B: the vertical first derivative of the magnetic anomaly, C: the magnetic anomaly after removing the background magnetic field residual, and D: the obtained linear background magnetic field residual.

[0096] Using the method of the present invention to Figure 4 The magnetic anomaly shown in Figure C underwent processing to eliminate the magnetic background field residual, resulting in the final magnetic anomaly after eliminating the background magnetic field residual. Figure 8 C in the equation and the residual of the eliminated background magnetic field ( Figure 8 (D) Because the linear background magnetic field residual fully meets the elimination conditions of the method of this invention, the obtained background magnetic anomaly residual and magnetic anomaly are completely consistent with the model. Eliminating the background magnetic field residual from the magnetic anomaly has achieved a very satisfactory result.

[0097] 8. Calculation results of multi-model simulation of magnetic anomaly and background magnetic field residuals using quadratic polynomial background magnetic field residuals: refer to Figure 9 , Figure 9 for Figure 5 A schematic diagram of the process and results of extracting the residual of the model background magnetic field, where A: the combined magnetic anomaly of the multi-model magnetic anomaly and the linear background magnetic field residual, B: the vertical first derivative of the magnetic anomaly, C: the magnetic anomaly after removing the background magnetic field residual, and D: the obtained background magnetic field residual.

[0098] Using the method of the present invention to Figure 5The magnetic anomaly shown in Figure C underwent processing to eliminate the magnetic background field residual, resulting in the final magnetic anomaly after eliminating the background magnetic field residual. Figure 9 C in the equation and the residual of the eliminated background magnetic field ( Figure 9 (D in the original text). Because the residual of the quadratic polynomial background magnetic field does not completely satisfy the elimination conditions of the method of the present invention, the obtained residual of the background magnetic anomaly and the magnetic anomaly are somewhat different from the model. This is mainly because the residual of the simulated quadratic polynomial background magnetic field still has the anomalous characteristics of the magnetic body, and its vertical first derivative is not completely zero.

[0099] The calculation results of the residual magnetic field of the measured magnetic anomaly in this invention: 1. Process for eliminating residual magnetic field in the background magnetic anomaly in the GLL region: refer to Figure 10 , Figure 10 The diagram shows the process of eliminating the background magnetic field residuals and the magnetic anomaly processing for eliminating the background magnetic field residuals in the GLL region. In the diagram, A: magnetic anomaly map of the GLL region, B: vertical first derivative of the magnetic anomaly in the GLL region, C: magnetic anomaly after eliminating the background magnetic field residuals, and D: eliminated background magnetic field residuals.

[0100] Using the method of the present invention to Figure 10 The magnetic anomaly in the GLL region shown in Figure A was processed to eliminate the magnetic background field residual, and finally the magnetic anomaly after eliminating the background magnetic field residual was obtained. Figure 10 C in the equation and the residual of the eliminated background magnetic field ( Figure 10 (D in the middle).

[0101] 2. Comparison of magnetic anomalies in the GLL region with magnetic anomaly profiles after eliminating background magnetic field residuals: refer to Figure 11 and Figure 12 By comparing the cross-sections of the magnetic anomaly in the GLL region before and after removing the background magnetic field residual, it can be seen that before removing the background magnetic field residual, the magnetic anomaly was almost a negative anomaly, while after removing the background magnetic field residual, the positive and negative amplitudes of the magnetic anomaly were reasonable.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] Furthermore, those skilled in the art will understand that aspects of this application can be described and illustrated through several patentable types or situations, including any new and useful combination of processes, machines, products, or substances, or any new and useful improvements thereof. Therefore, aspects of this application can be implemented entirely in hardware, entirely in software (including firmware, resident software, microcode, etc.), or a combination of hardware and software. All of the above hardware or software can be referred to as a “unit,” “module,” or “system.” Furthermore, aspects of this application can take the form of a computer program product embodied in one or more computer-readable media, wherein computer-readable program code is contained therein.

[0109] The computer program code required for the operation of each part of this application can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, and Python; general programming languages ​​such as C; Visual Basic, Fortran2103, Perl, COBOL2102, PHP, and ABAP; dynamic programming languages ​​such as Python, Ruby, and Groovy; or other programming languages. This program code can run entirely on the user's computer, or as a standalone software package on the user's computer, or partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer via any network, such as a local area network (LAN) or wide area network (WAN), or connected to an external computer (e.g., via the Internet), or in a cloud computing environment, or used as a service such as Software as a Service (SaaS).

[0110] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this application are not intended to limit the order of the processes and methods of this application. Although some currently considered useful embodiments of the invention have been discussed in the foregoing disclosure by way of various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments of this application. For example, although the implementation of the various components described above can be embodied in a hardware device, it can also be implemented as a purely software solution, such as an installation on an existing server or mobile device.

[0111] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this approach of the present application should not be construed as reflecting an intention that the claimed subject matter requires more features than expressly recited in each claim. Rather, the subject of the invention should possess fewer features than in any single embodiment described above.

Claims

1. A method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies, characterized in that, include: Step 1: Obtain the measured magnetic field data of the magnetic exploration area, and perform conventional correction and curvature leveling on the measured magnetic field data to obtain regular grid magnetic anomaly data on a unified elevation plane that includes the target magnetic anomaly and the residual background magnetic field. Step 2: Perform data augmentation on the regular grid magnetic anomaly data to obtain augmented grid magnetic anomaly data that meets the requirements of Fast Fourier Transform. Step 3: Perform Fast Fourier Transform on the expanded grid magnetic anomaly data to obtain frequency domain magnetic anomaly spectrum data; Step 4: Based on the physical characteristic that the residual background magnetic field is independent of the observation elevation, the vertical first derivative operation is performed on the frequency domain magnetic anomaly spectrum data to remove the spectral components corresponding to the residual background magnetic field, and obtain frequency domain vertical first derivative spectrum data containing only the target magnetic anomaly information. Step 5: Perform inverse fast Fourier transform on the frequency domain vertical first derivative spectrum data to obtain spatial domain vertical first derivative grid data. Step 6: Perform Fast Fourier Transform on the spatial domain vertical first derivative grid data to obtain the frequency domain vertical first derivative quadratic spectrum data. Step 7: Perform vertical integration on the frequency domain vertical first derivative quadratic spectrum data to reconstruct the target magnetic anomaly and obtain frequency domain integrated reconstructed spectrum data. Step 8: Perform inverse fast Fourier transform on the frequency domain integral restored spectrum data to obtain the expanded region background-removed magnetic anomaly grid data. Step 9: According to the grid range of the test area corresponding to the regular grid magnetic anomaly data, perform regional truncation processing on the background-removed magnetic anomaly grid data of the expanded area to obtain the target magnetic anomaly data of the test area after eliminating the residual background magnetic field.

2. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, The residual background magnetic field is the magnetic field component remaining after the measured magnetic field data has been conventionally corrected. It is independent of the observation elevation and only varies with the plane position. It includes at least one of the following: the daily variation correction base value deviation component caused by the selection deviation of the base value in the daily variation correction, the normal field calculation deviation component caused by the calculation deviation of the international geomagnetic reference field model, and the regional magnetic anomaly component caused by deep geological bodies.

3. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, In step one, the curvature-leveling process involves converting measured magnetic field data at different observation elevations into magnetic anomaly potential field curvature-leveling data, and uniformly reducing them to the same horizontal elevation plane to obtain regular grid magnetic anomaly data on that horizontal elevation plane.

4. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, In step two, the data augmentation process uses a cosine window function to symmetrically augment the regular grid magnetic anomaly data on all four sides. The number of survey lines and the number of measurement points on a single survey line in the augmented grid magnetic anomaly data are both integer powers of 2.

5. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, In step four, the vertical first derivative operation is based on the frequency domain conversion rule of the magnetic anomaly potential field. The frequency response operation of the vertical first derivative is performed on the frequency domain magnetic anomaly spectrum data to remove the spectral components corresponding to the residual background magnetic field that are independent of the elevation, so as to obtain the frequency domain vertical first derivative spectrum data containing only the target magnetic anomaly information.

6. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1 or 5, characterized in that, The frequency domain vertical first derivative spectrum data obtained in step four retains only the vertical variation spectrum component corresponding to the target magnetic anomaly, and completely removes the zero vertical variation spectrum component corresponding to the residual background magnetic field.

7. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, In step seven, the vertical integration operation is based on the frequency domain conversion rule of the magnetic anomaly potential field. It performs a frequency response operation on the frequency domain vertical first derivative second spectrum data to restore the frequency domain integrated restored spectrum data corresponding to the target magnetic anomaly.

8. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, In step four, during the vertical first derivative operation, the zero-frequency component in the frequency domain magnetic anomaly spectrum data is set to zero; and in step seven, during the vertical integration operation, the zero-frequency component in the frequency domain vertical first derivative second spectrum data is set to zero.

9. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, The measured magnetic field data comes from diamond nitrogen vacancy color center magnetic measurements. In step one, the routine calibration also includes probe attitude correction and temperature drift correction.

10. The method for eliminating residual background magnetic fields using the vertical first derivative and integral of magnetic anomalies according to claim 1, characterized in that, Following step nine, the following is also included: The regular grid magnetic anomaly data obtained in step one is compared with the target magnetic anomaly data obtained in step nine to obtain the residual background magnetic field data of the survey area. The residual background magnetic field data is then used for background field feature analysis in the geological interpretation of magnetic anomalies.

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