Modeling and calculation method of global lithospheric magnetic field model based on high-precision magnetic measurement

Abstract

The present invention proposes a modeling and calculation method of a global lithosphere magnetic field model based on high-precision magnetic survey, the method comprising: calculating a global scalar magnetic potential grid based on the initial Gaussian spherical harmonic coefficients of the global lithosphere magnetic field model to be refined; calculating the local scalar magnetic potential according to the normal geomagnetic field direction based on high-precision aviation and marine magnetic survey data; controlling the level of the local scalar magnetic potential through the global scalar magnetic potential grid, and splicing it to the global scalar magnetic potential grid; performing numerical modeling based on the scalar magnetic potential of the updated global lithosphere magnetic field model, solving to obtain the optimized Gaussian spherical harmonic coefficients; replacing the optimized Gaussian spherical harmonic coefficients with the Gaussian spherical harmonic coefficients of the lithosphere magnetic field model of 16 to 120 orders constructed by satellite magnetic survey, and synthesizing the final full-band lithosphere magnetic field model. The present invention solves the problem that it is difficult to quickly refine or update the global lithosphere magnetic field model through the latest acquired high-precision magnetic survey data.

Description

Technical Field

[0001] The present invention relates to the technical field of earth magnetic field measurement, and in particular to a global lithosphere magnetic field modeling and calculation method based on high-precision magnetic measurement. Background Art

[0002] The lithospheric magnetic field represents the magnetic field information originating from the Earth's lithosphere, especially the crust, and has important research value in many fields such as earth science, resource and energy exploration, passive navigation, guidance, and military defense. The lithospheric magnetic field model is a mathematical expression of the Earth's lithospheric magnetic field. The Gaussian spherical harmonic analysis method is currently the only mathematical method that can fully express the global lithospheric magnetic field model.

[0003] Through nearly a century of aeromagnetic and marine magnetic data collection and processing, data collection and collation, and integration of satellite magnetic data, we have compiled national, intercontinental and global lithospheric magnetic field data sets, namely the global magnetic anomaly grid, and constructed global lithospheric magnetic field models represented by the crustal magnetic field model NGDC-720. The established global lithospheric magnetic field models, such as the crustal magnetic field model NGDC-720 and the crustal magnetic field model EMM2017, all use the Gaussian spherical harmonic model, and give the standard form of the geomagnetic model in the form of Gaussian spherical harmonic coefficients with a reference earth radius of 6371.2 km. At present, the spherical harmonic coefficient expansion order is up to 1050. Despite this, the theoretical spatial resolution of the global lithospheric magnetic field model can only reach 40 km at best, so the accuracy of the actual global lithospheric magnetic field model is still low. Summary of the invention

[0004] The present invention provides a modeling and calculation method for a global lithospheric magnetic field model based on high-precision magnetic survey, the main purpose of which is to solve the problem that the global lithospheric magnetic field model is difficult to quickly update or refine through the latest acquired high-precision aeromagnetic survey and marine magnetic survey data.

[0005] In a first aspect, an embodiment of the present invention provides a global lithospheric magnetic field modeling and calculation method based on high-precision magnetic measurement, including:

[0006] S1, based on the initial Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model to be refined, calculate the global scalar magnetic potential grid corresponding to the lithospheric magnetic field model with a preset height from the reference earth and a wavelength less than 330km (corresponding to Gaussian spherical harmonic coefficients of 120th order or more);

[0007] S2, based on aeromagnetic survey data and marine magnetic survey data, the local scalar magnetic potential is calculated according to the normal geomagnetic field vector direction of the target area;

[0008] S3, controlling the level of the local scalar magnetic potential through the global scalar magnetic potential grid, splicing the local scalar magnetic potential grid to the global scalar magnetic potential grid, and realizing the update of the scalar magnetic potential of the global lithospheric magnetic field model to be refined;

[0009] S4, numerical modeling of the scalar magnetic potential based on the updated global lithospheric magnetic field model to obtain the optimized Gaussian spherical harmonic coefficients;

[0010] S5, replacing the optimized 16 to 120 order Gaussian spherical harmonic coefficients with the 16 to 120 order Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model constructed by satellite magnetic survey, synthesizing the final full-band lithospheric magnetic field model, so as to calculate the lithospheric magnetic field of the target area based on the full-band lithospheric magnetic field model.

[0011] Furthermore, the step S2 comprises:

[0012] S21, performing normal geomagnetic field correction, magnetic diurnal variation correction, and leveling processing on the aeromagnetic data and the marine magnetic data, and gridding to form a magnetic grid in a projected coordinate system, wherein the magnetic grid is not larger than the grid spacing in the global scalar magnetic potential grid;

[0013] S22, converting the magnetic measurement grid to the height of the global scalar magnetic potential grid through a frequency extension operator;

[0014] S23, filtering the calculated magnetic survey grid to remove the part with wavelength greater than 330 km;

[0015] S24, iteratively solving the filtered magnetic measurement grid and the normal magnetic field vector direction of the target area to obtain the local scalar magnetic potential.

[0016] Furthermore, the step S24 includes:

[0017] Firstly, an initial scalar magnetic potential is calculated according to the filtered magnetic measurement grid, and then the magnetic measurement grid is obtained by reverse calculation according to the initial scalar magnetic potential and the normal magnetic field vector direction of the target area;

[0018] Based on the difference between the filtered magnetic measurement grid and the magnetic measurement grid obtained by back calculation, if the difference is greater than a set threshold (e.g., 5 nT), the initial scalar magnetic potential is corrected, and the above steps are repeated until the corrected difference is less than the set threshold, and the corrected scalar magnetic potential is used as the local scalar magnetic potential;

[0019] If the difference is not greater than the set threshold, the initial scalar magnetic potential is used as the local scalar magnetic potential.

[0020] Furthermore, the step S3 comprises:

[0021] S31, quantifying the numerical difference between the grid overlap area of ​​the global scalar magnetic potential grid and the local scalar magnetic potential, and fitting the scalar magnetic potential difference between the global scalar magnetic potential grid and the local scalar magnetic potential by a low-order polynomial;

[0022] S32, adjusting the grid of the local scalar magnetic potential by using the fitted scalar magnetic potential difference, so that the adjusted grid of the local scalar magnetic potential is consistent with the background trend of the global scalar magnetic potential grid;

[0023] S33, resampling the adjusted local scalar magnetic potential grid to adapt to the specifications of the global scalar magnetic potential grid;

[0024] S34, splicing the resampled local scalar magnetic potential grid to the global scalar magnetic potential grid in a weighted manner.

[0025] Furthermore, the step S34 is implemented by the following formula:

[0026] V=w·V Globe +(1-w)·V Local ;

[0027] Wherein, V represents the scalar magnetic potential value, the subscript Globle represents the global scalar magnetic potential grid, the subscript Local represents the local scalar magnetic potential grid, and w is the weight, which varies from 1 to 0 according to the distance from the overlapping grid point.

[0028] Furthermore, the step S4 comprises:

[0029] Based on numerical integration, the scalar magnetic potential of the updated global lithospheric magnetic field model is numerically modeled to obtain the intermediate Gaussian spherical harmonic coefficients;

[0030] The intermediate Gaussian spherical harmonic coefficients are converted and extended to obtain optimized Gaussian spherical harmonic coefficients.

[0031] Furthermore, the reference global lithospheric magnetic field model is the global lithospheric magnetic field model to be refined, or the global lithospheric magnetic field model obtained by satellite magnetic survey modeling.

[0032] In a second aspect, an embodiment of the present invention provides a lithospheric magnetic field modeling system of a global lithospheric magnetic field model using high-precision magnetic measurement, comprising:

[0033] An initial module is used to calculate the global scalar magnetic potential grid corresponding to the lithosphere magnetic field model with a preset height from the reference earth and a wavelength less than 330 km (corresponding to Gaussian spherical harmonic coefficients of 120th order or higher) based on the initial Gaussian spherical harmonic coefficients of the global lithosphere magnetic field model to be refined;

[0034] The local module is used to calculate the local scalar magnetic potential according to the normal magnetic field vector direction of the target area based on the aeromagnetic survey data and marine magnetic survey data;

[0035] An updating module, used for controlling the level of the local scalar magnetic potential through the global scalar magnetic potential grid, splicing the grid of the local scalar magnetic potential to the global scalar magnetic potential grid, and realizing the update of the scalar magnetic potential of the global lithospheric magnetic field model to be refined;

[0036] Modeling module, used to perform numerical modeling based on the scalar magnetic potential of the updated global lithospheric magnetic field model and solve for the optimized Gaussian spherical harmonic coefficients;

[0037] A synthesis module is used to replace the optimized 16- to 120-order Gaussian spherical harmonic coefficients with the 16- to 120-order Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model constructed by satellite magnetic measurement, and synthesize the final full-band lithospheric magnetic field model to calculate the lithospheric magnetic field of the target area based on the full-band lithospheric magnetic field model.

[0038] In a third aspect, an embodiment of the present invention provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for modeling a global lithospheric magnetic field model based on high-precision magnetic measurement and calculating the lithospheric magnetic field when executing the computer program.

[0039] In a fourth aspect, an embodiment of the present invention provides a computer storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for modeling and calculating a global lithospheric magnetic field model based on high-precision magnetic measurement.

[0040] The present invention proposes a global lithosphere magnetic field model modeling and calculation method based on high-precision magnetic survey. It only needs to replace the scalar magnetic potential grid corresponding to the 120th order or more of the low-precision area in the reference global lithosphere magnetic field model. The scalar magnetic potential of the replaced part is determined by high-precision aeromagnetic survey and marine magnetic survey data. The scalar magnetic potential grid of the global lithosphere magnetic field is updated by a grid splicing method, and then the corresponding Gaussian spherical harmonic coefficients are directly calculated by a high-precision numerical integration algorithm. The present invention avoids reorganizing and remodeling the lithosphere magnetic field data set of the global scale, realizes efficient data fusion, and greatly shortens the update cycle of the Gaussian spherical harmonic coefficients of the lithosphere magnetic field model. The method has high computational efficiency, adopts the integration method instead of the least squares iterative solution, and can complete the update or refinement of the global lithosphere magnetic field model in a relatively short time. At the same time, due to the high computational efficiency, when the accuracy of the magnetic survey data is high enough, the spherical harmonic coefficient order of the global lithosphere magnetic field model can be increased to more than 10,000 orders. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flow chart of a method for modeling and calculating a global lithospheric magnetic field model based on high-precision magnetic measurement provided by an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of the structure of a global lithosphere magnetic field modeling and calculation system based on high-precision magnetic measurement provided by an embodiment of the present invention;

[0043] Figure 3 A schematic diagram of the structure of a computer device provided in an embodiment of the present invention.

[0044] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0045] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0046] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0047] In the embodiments of the present application, at least one refers to one or more; multiple refers to two or more. In the description of the present application, words such as "first", "second", "third", etc. are only used to distinguish the purpose of description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0048] References to "one embodiment" or "some embodiments" etc. described in this specification mean that one or more embodiments of the present application include a particular feature, structure or characteristic described in conjunction with the embodiment. Thus, in this specification, the terms "include", "comprises", "has" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0049] In addition to low accuracy, existing lithospheric magnetic field calculation methods also have data gaps in some areas of the global-scale lithospheric magnetic field dataset due to aeromagnetic and marine magnetic surveys. Therefore, the actual resolution of the global lithospheric magnetic field model in the data gap areas of the above-mentioned aeromagnetic and marine magnetic surveys is only 330km (corresponding to Gaussian spherical harmonic coefficients no higher than 120th order), which will seriously restrict the application of the lithospheric magnetic field model.

[0050] The global lithospheric magnetic field model is modeled using the Gaussian spherical harmonic analysis method. Since both aeromagnetic and marine magnetic survey data are anomaly data of the total intensity of the geomagnetic field, the construction of the Gaussian spherical harmonic coefficient model must be achieved through geophysical inversion. The modeling process is difficult and time-consuming. For example, the NGDC-720 lithospheric magnetic field model was established using a commercial solver for parallel computing on a 3GHz quad-core CPU server, but it still took several months to complete the modeling.

[0051] With the continuous updating of high-precision aeromagnetic and marine magnetic survey data, the traditional technical means to update or refine the global lithospheric magnetic field model, even if the local extremely small area is updated, must recompile the global scale lithospheric magnetic field data set (global magnetic anomaly grid), and rebuild a new global lithospheric magnetic field model. This data update or refinement process is very costly, so once the global lithospheric magnetic field model is established, it faces the scientific problem of being difficult to continuously upgrade. For example, NGDC-720 has never been updated in more than 20 years since its establishment, and EMM2017 has never been updated in more than 7 years since its establishment.

[0052] In view of the above problems, an embodiment of the present invention provides a global lithospheric magnetic field modeling and calculation method based on high-precision magnetic measurement. Figure 1 A flowchart of a global lithosphere magnetic field modeling and calculation method based on high-precision magnetic measurement provided by an embodiment of the present invention, such as Figure 1 As shown, the method includes:

[0053] S1, based on the initial Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model to be refined, calculate the global scalar magnetic potential grid corresponding to the lithospheric magnetic field model with a preset height from the reference earth and a wavelength less than 330km (corresponding to Gaussian spherical harmonic coefficients of 120th order or more);

[0054] In the embodiment of the present invention, Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model to be refined are used to calculate the global scalar magnetic potential grid, wherein the global lithospheric magnetic field model to be refined may be an existing model such as the NGDC-720 model.

[0055] The global scalar magnetic potential grid calculation equation is as follows:

[0056]

[0057] Among them, r is the distance from the center of the earth, a = 6371.2km is the reference radius of the earth, θ is the co-latitude, λ is the longitude, and is the Gaussian spherical harmonic coefficient of the lithosphere magnetic field model of order n and m, is the associated Legendre function of Schmidt quasi-normalized order m, and N is the maximum order of the expansion of the lithospheric magnetic field model.

[0058] In the global scalar magnetic potential grid calculation equation in the embodiment of the present invention, the parameters are set as r=a+h, l=121, that is, only the global scalar magnetic potential grid corresponding to the global lithospheric magnetic field model with a height of h from the reference earth and a wavelength less than 330km (corresponding to Gaussian spherical harmonic coefficients of order 120 or above) is calculated, where h≥0, the unit is km, and h is the preset height.

[0059] It should be noted that the wavelength is less than 330 km, which corresponds to Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model above the 120th order.

[0060] In addition, the global scalar magnetic potential grid is divided into equiangular grids of size L×2L, that is, the grid point spacing satisfies Δθ=Δλ=π / L. If the maximum order of expansion of the lithospheric magnetic field model is N, then L at least satisfies L≥2N+1.

[0061] S2, based on aeromagnetic survey data and marine magnetic survey data, the local scalar magnetic potential is calculated according to the normal geomagnetic field vector direction of the target area;

[0062] Using aeromagnetic data and marine magnetic survey data, according to the normal magnetic field (main magnetic field) vector B of the target area x ,B y ,B z >Calculate the local scalar magnetic potential. The specific Fourier domain calculation equation is as follows:

[0063]

[0064] Among them, F[g] represents the Fourier transform, F -1 [g] represents inverse Fourier transform, i 2 =-1, u, v are the wave numbers in the x and y directions, B0= 0x ,B​​0y ,B 0z >Take the normal magnetic field vector B of the target area= x ,B y ,B z > the average value.

[0065] As an implementation manner, the step S2 includes:

[0066] S21, performing normal geomagnetic field correction, magnetic diurnal variation correction, and leveling processing on the aeromagnetic data and the marine magnetic data, and gridding to form a magnetic grid in a projected coordinate system, wherein the magnetic grid is not larger than the grid spacing in the global scalar magnetic potential grid;

[0067] S22, converting the magnetic measurement grid to the height of the global scalar magnetic potential grid through a frequency extension operator;

[0068] Since the magnetic grid obtained in S21 is usually not located at the height h of the reference earth used in step S1, it is necessary to use a frequency domain extension operator to convert the magnetic grid to this height. The frequency domain extension operator is Δh is the extension distance, which is positive when it is upward and negative when it is downward.

[0069] S23, filtering the calculated magnetic survey grid to remove the part with wavelength greater than 330 km;

[0070] S24, iteratively solving the filtered magnetic measurement grid and the target geomagnetic field vector to obtain the local scalar magnetic potential.

[0071] If the area of ​​the filtered magnetic measurement grid is large, the normal magnetic field vector B = x ,B y ,B z >The changes are large and iterative solutions need to be considered.

[0072] As an example, step S24 includes:

[0073] Firstly, an initial scalar magnetic potential is calculated according to the filtered magnetic measurement grid, and then the magnetic measurement grid is obtained by reverse calculation according to the initial scalar magnetic potential and the normal magnetic field vector direction of the target area;

[0074] Based on the difference between the filtered magnetic measurement grid and the magnetic measurement grid obtained by back calculation, if the difference is greater than a set threshold (e.g., 5 nT), the initial scalar magnetic potential is corrected, and the above steps are repeated until the corrected difference is less than the set threshold, and the corrected scalar magnetic potential is used as the local scalar magnetic potential;

[0075] If the difference is not greater than the set threshold, the initial scalar magnetic potential is used as the local scalar magnetic potential.​​

[0076] The threshold value may be generally set to 5 nT according to the magnetic measurement accuracy.

[0077] In the embodiment of the present invention, the initial scalar magnetic potential is calculated using the filtered magnetic measurement grid, and then the magnetic measurement grid is inversely calculated using the obtained initial scalar magnetic potential. The difference between the filtered magnetic measurement grid and the inversely calculated magnetic measurement grid is calculated, and the scalar magnetic potential is corrected using the difference.

[0078] This iteration is repeated and convergence can be achieved after several iterations. It is usually required that the error between the magnetic survey grid obtained by backcalculation and the magnetic survey grid after airborne magnetic survey and marine magnetic survey filtering is less than a set threshold.

[0079] According to the initial scalar magnetic potential and the target geomagnetic field vector, the magnetic survey grid formula is obtained by inverse calculation:

[0080]

[0081] S3, controlling the level of the local scalar magnetic potential through the global scalar magnetic potential grid, splicing the local scalar magnetic potential grid to the global scalar magnetic potential grid, and realizing the update of the scalar magnetic potential of the global lithospheric magnetic field model to be refined;

[0082] As an implementation manner, the step S3 includes:

[0083] S31, quantifying the numerical difference between the grid overlap area of ​​the global scalar magnetic potential grid and the local scalar magnetic potential, and fitting the scalar magnetic potential difference between the global scalar magnetic potential grid and the local scalar magnetic potential through a polynomial;

[0084] Among them, the numerical difference in the overlapping area of ​​the global scalar magnetic potential grid and the local scalar magnetic potential grid is quantified, and the scalar magnetic potential difference between the two is fitted by a polynomial, and the fitting polynomial is required to be no more than third order.

[0085] S32, adjusting the grid of the local scalar magnetic potential by using the fitted scalar magnetic potential difference, so that the adjusted grid of the local scalar magnetic potential is consistent with the background trend of the global scalar magnetic potential grid;

[0086] The local scalar magnetic potential grid is adjusted using the fitting polynomial to obtain an adjusted local scalar magnetic potential grid, wherein the adjusted local scalar magnetic potential grid is consistent with the background trend of the global scalar magnetic potential grid.

[0087] S33, resampling the adjusted local scalar magnetic potential grid to adapt to the specifications of the global scalar magnetic potential grid;

[0088] The adjusted local scalar magnetic potential grid is resampled to fit the specifications of the global scalar magnetic potential grid. Resampling includes adjusting the grid cell size to the global scalar magnetic potential grid cell size, and also adjusting the grid offset to the offset of the global scalar magnetic potential grid to ensure that the grid points of the two grids completely coincide.

[0089] S34, splicing the resampled local scalar magnetic potential grid to the global scalar magnetic potential grid in a weighted manner.

[0090] The resampled local scalar magnetic potential grid is spliced ​​to the global scalar magnetic potential grid in a weighted manner, namely:

[0091] V=w·V Globe +(1-w)·V Local ;

[0092] Among them, V represents the scalar magnetic potential value, the subscript Global represents the global scalar magnetic potential grid, and the subscript Local represents the local scalar magnetic potential grid; w is the weight that varies from 1 to 0 according to the distance from the overlapping grid point.

[0093] Therefore, the edge of the local scalar magnetic potential grid transitions smoothly with the global scalar magnetic potential grid, ensuring that the new global scalar magnetic potential grid obtained after splicing is the local scalar magnetic potential in the overlapping area and the global scalar magnetic potential outside the overlapping area, and the several grid points between the two (edges of the overlapping area) can transition smoothly.

[0094] S4, numerical modeling of the scalar magnetic potential based on the updated global lithospheric magnetic field model to obtain the optimized Gaussian spherical harmonic coefficients;

[0095] As an implementation manner, the step S4 includes:

[0096] Based on numerical integration, the scalar magnetic potential of the updated global lithospheric magnetic field model is numerically modeled to obtain the intermediate Gaussian spherical harmonic coefficients;

[0097] The intermediate Gaussian spherical harmonic coefficients are converted and extended to obtain optimized Gaussian spherical harmonic coefficients.

[0098] After obtaining the updated or refined scalar magnetic potential grid of the global lithospheric magnetic field model, the scalar magnetic potential can be numerically modeled and the spherical harmonic coefficients can be solved. The calculation equation of the spherical harmonic coefficients is as follows:

[0099]

[0100] in and is the spherical harmonic coefficient of order n and degree m, V is the global scalar magnetic potential, θ is the co-latitude, and λ is the longitude. However, the double integral process of the spherical harmonic coefficient calculation is not stable. In the actual calculation, the integral is decomposed into two one-dimensional integrals in the longitude direction and the co-latitude direction, and the Driscoll / Healy sampling theory is used for integral calculation. The specific algorithm is as follows:

[0101] Calculate the integral in the longitude direction,

[0102]

[0103] in:

[0104]

[0105] The integral can be directly calculated in discrete form. Since the integral term sine and cosine function basis is essentially a one-dimensional Fourier transform, the fast Fourier transform algorithm (FFT) can be directly used to accelerate the calculation in discrete calculation.

[0106] Calculate the integral in the co-latitude direction, and we have

[0107]

[0108] Since the global scalar magnetic potential grid with equal spacing (Δθ=Δλ=π / L) is used for calculation, the scalar magnetic potential nodes are sparse at the equator in the actual co-latitude direction, but dense at the poles, so the numerical integration of the Legendre function is still unstable. The numerical integration uses the Driscoll / Healy sampling theory for weighted processing, which greatly improves the accuracy of the Legendre function integration.

[0109] Since the above numerical integration does not take into account the influence of the earth's radius (it is only the spherical harmonic integral of unit radius 1), the spherical harmonic coefficients obtained by numerical integration are still not the Gaussian spherical harmonic coefficients of the earth's reference radius (a = 6371.2km), and they need to be converted and extended. The specific calculation equation is:

[0110]

[0111] Wherein, r is the geocentric distance of the global scalar magnetic potential calculated in step S1, that is, r=a+h.

[0112] The maximum expansion order for the above spherical harmonic coefficient calculation is N, which is generally consistent with the maximum expansion order of the lithospheric magnetic field model to be updated or refined. If the updated or refined area is large, the expansion order can be appropriately increased according to the shape of the power spectrum.

[0113] S5, replacing the optimized 16 to 120 order Gaussian spherical harmonic coefficients with the 16 to 120 order Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model constructed by satellite magnetic survey, synthesizing the final full-band lithospheric magnetic field model, so as to calculate the lithospheric magnetic field of the target area based on the full-band lithospheric magnetic field model.

[0114] The wavelength of the lithospheric magnetic field reflected by near-surface magnetic surveys such as aeromagnetic surveys and marine magnetic surveys in the embodiments of the present invention is usually less than 330 km, corresponding to Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model of order 120 or above.

[0115] Since the 16th to 120th order Gaussian spherical harmonic coefficients in step 1 correspond to the lithospheric magnetic field with a wavelength greater than 330 km, the coefficients of the 120th order and below in the Gaussian spherical harmonic coefficients determined in the previous step are inaccurate, and it is necessary to replace the coefficients of the 120th order and below to synthesize the final full-band lithospheric magnetic field model.

[0116] As an example, the reference global lithospheric magnetic field model is the global lithospheric magnetic field model to be refined, or the global lithospheric magnetic field model obtained by satellite magnetic modeling.

[0117] There are two replacement methods. One is to replace the Gaussian spherical harmonic coefficients of order 120 and below in the global lithospheric magnetic field model to be updated or refined. The other is to replace the Gaussian spherical harmonic coefficients of order 120 and below in the global lithospheric magnetic field model built by satellite magnetic measurement.

[0118] The global lithospheric magnetic field model constructed by satellite magnetic surveying can adopt the latest MF model, etc. The advantage of this is that it can update the long-wavelength part of the global lithospheric magnetic field model longer than 330 km.

[0119] In summary, by gradually implementing steps S1 to S5, the global lithospheric magnetic field model based on high-precision magnetic measurement can be quickly updated or refined, and the final global lithospheric magnetic field model (the model is expressed in the form of Gaussian spherical harmonic coefficients) can be obtained, thereby realizing the version update of the existing global lithospheric magnetic field model (such as NGDC-720, EMM2017, etc.).

[0120] The present invention proposes a global lithosphere magnetic field modeling and calculation method based on high-precision magnetic survey. It only needs to replace the scalar magnetic potential grid corresponding to the 120th order or more of the low-precision area in the reference global lithosphere magnetic field model. The scalar magnetic potential of the replaced part is determined by high-precision aeromagnetic survey and marine magnetic survey data. The scalar magnetic potential grid of the global lithosphere magnetic field is updated by a grid splicing method, and then the corresponding Gaussian spherical harmonic coefficients are directly calculated by a high-precision numerical integration algorithm. The present invention avoids reorganizing and remodeling the lithosphere magnetic field data set of the global scale, realizes efficient data fusion, and greatly shortens the update cycle of the lithosphere magnetic field model coefficient. The method has high computational efficiency, adopts the integral method instead of the least squares iterative solution, and can complete the update or refinement of the global lithosphere magnetic field model in a shorter time on a PC. At the same time, due to the high computational efficiency, when the accuracy of the magnetic survey data is high enough, the spherical harmonic coefficient order of the global lithosphere magnetic field model can be increased to more than 10,000 orders.

[0121] Figure 2 A structural schematic diagram of a global lithosphere magnetic field modeling and calculation system based on high-precision magnetic measurement provided by an embodiment of the present invention, such as Figure 2 As shown, the system includes:

[0122] The initial module 210 is used to calculate the global scalar magnetic potential grid corresponding to the lithosphere magnetic field model with a preset height from the reference earth and a wavelength less than 330 km based on the initial Gaussian spherical harmonic coefficients of the global lithosphere magnetic field model to be refined;

[0123] The local module 220 is used to calculate the local scalar magnetic potential according to the normal geomagnetic field vector direction of the target area based on the aeromagnetic survey data and the marine magnetic survey data;

[0124] The updating module 230 is used to control the level of the local scalar magnetic potential through the global scalar magnetic potential grid, splice the grid of the local scalar magnetic potential to the global scalar magnetic potential grid, and realize the update of the scalar magnetic potential of the global lithospheric magnetic field model to be refined;

[0125] The modeling module 240 is used to perform numerical modeling based on the scalar magnetic potential of the updated global lithospheric magnetic field model to obtain optimized Gaussian spherical harmonic coefficients;

[0126] The synthesis module 250 is used to replace the optimized 16 to 120 order Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model constructed by satellite magnetic measurement with the 16 to 120 order Gaussian spherical harmonic coefficients to synthesize the final full-band lithospheric magnetic field model, so as to calculate the lithospheric magnetic field of the target area based on the full-band lithospheric magnetic field model.

[0127] This embodiment is a system embodiment corresponding to the above method embodiment, and its specific implementation process is the same as the above method embodiment. For details, please refer to the above method embodiment, and this system embodiment will not be repeated here.

[0128] Each module in the lithospheric magnetic field calculation system of the global lithospheric magnetic field model of the above-mentioned high-precision magnetic survey can be implemented in whole or in part by software, hardware and their combination. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0129] Figure 3 A schematic diagram of the structure of a computer device provided in an embodiment of the present invention, the computer device may be a server, and its internal structure diagram may be as follows Figure 3 As shown. The computer device includes a processor, a memory, a network interface and a database connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a computer storage medium and an internal memory. The computer storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the computer storage medium. The database of the computer device is used to store data generated or obtained during the execution of a global lithospheric magnetic field modeling and calculation method based on high-precision magnetic measurement. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a global lithospheric magnetic field modeling and calculation method based on high-precision magnetic measurement is implemented.

[0130] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method for calculating the lithospheric magnetic field of a global lithospheric magnetic field model based on high-precision magnetic survey in the above embodiment are implemented. Alternatively, when the processor executes the computer program, the functions of each module / unit in the embodiment of a global lithospheric magnetic field modeling and calculation system based on high-precision magnetic survey are implemented.

[0131] In one embodiment, a computer storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of a method for modeling and calculating a global lithospheric magnetic field model based on high-precision magnetic survey in the above embodiment are implemented. Alternatively, when the computer program is executed by a processor, the functions of each module / unit in the embodiment of a lithospheric magnetic field calculation system for a global lithospheric magnetic field model based on high-precision magnetic survey are implemented.

[0132] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0133] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0134] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A global lithosphere magnetic field modeling and calculation method based on high-precision magnetic measurement, characterized in that: include: S1, based on the initial Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model to be refined, calculate the global scalar magnetic potential grid corresponding to the lithospheric magnetic field model with a preset height from the reference earth and a wavelength less than 330 km; S2, based on aeromagnetic survey data and marine magnetic survey data, the local scalar magnetic potential is calculated according to the normal geomagnetic field vector direction of the target area; S3, controlling the level of the local scalar magnetic potential through the global scalar magnetic potential grid, splicing the local scalar magnetic potential grid to the global scalar magnetic potential grid, and realizing the update of the scalar magnetic potential of the global lithospheric magnetic field model to be refined; S4, numerical modeling based on the updated scalar magnetic potential of the global lithospheric magnetic field to obtain the optimized Gaussian spherical harmonic coefficients; S5, replacing the optimized 16 to 120 order Gaussian spherical harmonic coefficients with the 16 to 120 order Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model constructed by satellite magnetic survey, synthesizing the final full-band lithospheric magnetic field model, so as to calculate the lithospheric magnetic field of the target area based on the full-band lithospheric magnetic field model.

2. The global lithosphere magnetic field modeling and calculation method based on high-precision magnetic measurement according to claim 1 is characterized in that: The step S2 comprises: S21, performing normal geomagnetic field correction, magnetic diurnal variation correction, and leveling processing on the aeromagnetic data and the marine magnetic data, and gridding to form a magnetic grid in a projected coordinate system, wherein the magnetic grid is not larger than the grid spacing in the global scalar magnetic potential grid; S22, converting the magnetic measurement grid to the height of the global scalar magnetic potential grid through a frequency extension operator; S23, filtering the calculated magnetic survey grid to remove the part with wavelength greater than 330 km; S24, performing iterative solution on the filtered magnetic measurement grid using the normal magnetic field vector direction of the target area to obtain the local scalar magnetic potential.

3. The global lithosphere magnetic field modeling and calculation method based on high-precision magnetic measurement according to claim 2 is characterized in that: The step S24 comprises: Firstly, an initial scalar magnetic potential is calculated according to the filtered magnetic measurement grid, and then the magnetic measurement grid is obtained by reverse calculation according to the initial scalar magnetic potential and the normal magnetic field vector direction of the target area; Based on the difference between the filtered magnetic measurement grid and the magnetic measurement grid obtained by back calculation, if the difference is greater than a set threshold, the initial scalar magnetic potential is corrected, and the above steps are repeated until the corrected difference is less than the set threshold, and the corrected scalar magnetic potential is used as the local scalar magnetic potential; If the difference is not greater than the set threshold, the initial scalar magnetic potential is used as the local scalar magnetic potential.

4. The method for modeling and calculating the global lithospheric magnetic field model based on high-precision magnetic measurement according to claim 1, characterized in that: The step S3 comprises: S31, quantifying the numerical difference between the grid overlap area of ​​the global scalar magnetic potential grid and the local scalar magnetic potential, and fitting the scalar magnetic potential difference between the global scalar magnetic potential grid and the local scalar magnetic potential by a low-order polynomial; S32, adjusting the grid of the local scalar magnetic potential by using the fitted scalar magnetic potential difference, so that the adjusted grid of the local scalar magnetic potential is consistent with the background trend of the global scalar magnetic potential grid; S33, resampling the adjusted local scalar magnetic potential grid to adapt to the specifications of the global scalar magnetic potential grid; S34, splicing the resampled local scalar magnetic potential grid to the global scalar magnetic potential grid in a weighted manner.

5. The method for modeling and calculating the global lithosphere magnetic field model based on high-precision magnetic measurement according to claim 4 is characterized in that: The step S34 is implemented by the following formula: V=w·V Globe +(1-w)·V Local ; Wherein, V represents the scalar magnetic potential value, the subscript Globle represents the global scalar magnetic potential grid, the subscript Local represents the local scalar magnetic potential grid, and w is the weight, which varies from 1 to 0 according to the distance from the overlapping grid point.

6. The method for modeling and calculating the global lithosphere magnetic field model based on high-precision magnetic measurement according to claim 1, characterized in that: The step S4 comprises: Based on numerical integration, the updated global lithospheric magnetic field scalar potential is numerically modeled to obtain intermediate Gaussian spherical harmonic coefficients. The intermediate Gaussian spherical harmonic coefficients are converted and extended to obtain optimized Gaussian spherical harmonic coefficients.

7. The method for modeling and calculating the global lithospheric magnetic field model based on high-precision magnetic measurement according to claim 1, characterized in that: The reference global lithospheric magnetic field model is the global lithospheric magnetic field model to be refined, or the global lithospheric magnetic field model obtained by satellite magnetic survey modeling.

8. A global lithosphere magnetic field modeling and calculation system based on high-precision magnetic measurement, characterized in that: include: An initial module is used to calculate the global scalar magnetic potential grid corresponding to the lithosphere magnetic field model with a preset height from the reference earth and a wavelength less than 330 km based on the initial Gaussian spherical harmonic coefficients of the global lithosphere magnetic field model to be refined; The local module is used to calculate the local scalar magnetic potential based on the aeromagnetic data and marine magnetic data according to the direction of the normal geomagnetic field vector in the target area; An updating module, used for controlling the level of the local scalar magnetic potential through the global scalar magnetic potential grid, splicing the grid of the local scalar magnetic potential to the global scalar magnetic potential grid, and realizing the update of the scalar magnetic potential of the global lithospheric magnetic field model to be refined; Modeling module, used to perform numerical modeling based on the scalar magnetic potential of the updated global lithospheric magnetic field model and solve for the optimized Gaussian spherical harmonic coefficients; A synthesis module is used to replace the optimized 16- to 120-order Gaussian spherical harmonic coefficients with the 16- to 120-order Gaussian spherical harmonic coefficients of the global lithospheric magnetic field model constructed by satellite magnetic measurement, and synthesize the final full-band lithospheric magnetic field model to calculate the lithospheric magnetic field of the target area based on the full-band lithospheric magnetic field model.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for modeling and calculating the global lithospheric magnetic field model based on high-precision magnetic measurement as described in any one of claims 1 to 7 are implemented.

10. A computer storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for modeling and calculating the global lithospheric magnetic field model based on high-precision magnetic measurement as described in any one of claims 1 to 7 are implemented.

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