Aviation magnetic detection platform magnetic interference ground calibration method and system

Abstract

The invention discloses a magnetic interference ground calibration method and system for an aviation magnetic detection platform, and relates to the technical field of aviation magnetic detection. The calibration method comprises the following steps: placing equipment carrying a magnetic sensor in a ground environment without strong magnetic interference, and collecting geomagnetic field data by using the magnetic sensor; for the static geomagnetic field data, extracting a diurnal variation magnetic field interference component by using wavelet transform, frequency domain mapping and time domain correction; enabling the equipment to move along a preset track, recording measured geomagnetic field data on the motion track, and obtaining a geomagnetic background component by using a method in geomagnetic navigation based on the measured geomagnetic field data; the method comprises the following steps: slowly rotating equipment, and extracting a dynamic magnetic interference component generated by platform movement by using Fourier transform and filtering processing for dynamic geomagnetic field data; and subtracting the three components from the geomagnetic field data to obtain a measurement noise component, thereby obtaining each calibrated magnetic interference component. According to the method, hardware except a magnetic sensor is not needed, and each extracted calibration magnetic interference component is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of airborne magnetic exploration, and particularly to a method and system for ground calibration of magnetic interference of an airborne magnetic exploration platform. Background Art

[0002] Airborne magnetic exploration systems are widely used in fields such as geological exploration, environmental monitoring, and military detection. However, the electromagnetic devices, structural materials of the airborne platform, and external environmental factors will introduce complex magnetic interference, significantly affecting the magnetic exploration accuracy. Existing calibration methods mainly rely on dynamic flight calibration, which is costly and vulnerable to environmental influences, and it is difficult to meet the requirements of rapid deployment and high precision.

[0003] In view of these problems, there is an urgent need to develop an efficient method that can be calibrated in a ground environment. Summary of the Invention

[0004] Therefore, the present invention proposes a method and system for ground calibration of magnetic interference of an airborne magnetic exploration platform.

[0005] According to one aspect of the present invention, a method for ground calibration of magnetic interference of an airborne magnetic exploration platform is proposed. The method includes:

[0006] Placing a device equipped with a magnetic sensor in a ground environment without strong magnetic interference, and using the magnetic sensor to collect geomagnetic field data; the geomagnetic field data includes a geomagnetic background component, a daily variation magnetic field interference component, a dynamic magnetic interference component generated by platform movement, and a measurement noise component;

[0007] For the collected static geomagnetic field data, using wavelet transform, frequency-domain mapping, and time-domain correction to extract the daily variation magnetic field interference component;

[0008] Presetting a device movement trajectory, making the device move along the preset trajectory, recording the measured geomagnetic field data on this movement trajectory, and obtaining the geomagnetic background component based on the measured geomagnetic field data using the method in geomagnetic navigation;

[0009] Making the device rotate slowly, and for the collected dynamic geomagnetic field data, using Fourier transform and filtering processing to extract the dynamic magnetic interference component generated by platform movement;

[0010] Subtracting the geomagnetic background component, the daily variation magnetic field interference component, and the dynamic magnetic interference component generated by platform movement from the geomagnetic field data to obtain the measurement noise component; thus obtaining each calibrated magnetic interference component.

[0011] Furthermore, subtracting each calibrated magnetic interference component from the geomagnetic field data collected by the magnetic sensor during the movement of the magnetic exploration platform to obtain the corrected geomagnetic field data.

[0012] Further, the extraction of the daily-varying magnetic field interference component by using wavelet transform, frequency-domain mapping, and time-domain correction includes:

[0013] For the static geomagnetic field data, apply the wavelet decomposition method to decompose the geomagnetic field signal into sub-band components of different scales, and then obtain the daily-varying magnetic field interference component with high-frequency noise;

[0014] Perform Fourier transform on the daily-varying magnetic field interference component with high-frequency noise to obtain the corresponding frequency-domain mapping;

[0015] Use a low-pass filter to filter the frequency-domain mapping to obtain the low-frequency component;

[0016] Perform inverse Fourier transform on the filtered low-frequency component to obtain the daily-varying magnetic field interference component with high-frequency noise removed.

[0017] Further, the obtaining of the geomagnetic background component based on the measured geomagnetic field data by using the method in geomagnetic navigation includes:

[0018] The measured geomagnetic field data includes continuous background geomagnetic field signals and local magnetic field perturbation signals;

[0019] Perform smoothing processing on the measured geomagnetic field data to obtain continuous background geomagnetic field signals;

[0020] Map the continuous background geomagnetic field signals to the entire ground measurement site through linear interpolation to construct a site background magnetic field model, and use the site background magnetic field model to obtain the geomagnetic background component; where the site background magnetic field model is:

[0021]

[0022] In the formula, n represents the number of trajectory points used in the interpolation; B bg (t i ) represents the geomagnetic background corresponding to time t i ; represents the distance between the point to be solved with weight p and trajectory point i or j, and the weight p is used to control the sensitivity to the change with distance; (x, y) represents the position coordinates of the measurement point.

[0023] Further, the extraction of the dynamic magnetic interference component generated by platform movement by using Fourier transform and filtering processing includes:

[0024] Perform fast Fourier transform on the collected dynamic geomagnetic field data to obtain the frequency-domain representation; where the frequency-domain representation of the dynamic geomagnetic field data includes the dynamic magnetic interference component and the DC geomagnetic field component;

[0025] Filter the frequency-domain representation of the dynamic geomagnetic field data to separate and obtain the frequency characteristics of the dynamic magnetic interference component;

[0026] Convolve the frequency characteristics of the dynamic magnetic interference component with a convolution kernel to obtain a convolution result; the convolution result is the dynamic magnetic interference component generated by the platform movement.

[0027] Furthermore, the convolution kernel is a high-pass filtering kernel.

[0028] According to another aspect of the present invention, a ground calibration system for magnetic interference of an airborne magnetic exploration platform is proposed, and the system includes:

[0029] A geomagnetic data acquisition module, which is configured to place a device equipped with a magnetic sensor in a ground environment without strong magnetic interference, and use the magnetic sensor to acquire static geomagnetic field data; preset a device movement trajectory, enable the device to move along the preset trajectory, and use the magnetic sensor to acquire measured geomagnetic field data on the movement trajectory; enable the device to rotate slowly, and use the magnetic sensor to acquire dynamic geomagnetic field data; the geomagnetic field data includes a geomagnetic background component, a daily variation magnetic field interference component, a dynamic magnetic interference component generated by platform movement, and a measurement noise component;

[0030] A magnetic interference component extraction module, which is configured to, for the acquired static geomagnetic field data, extract the daily variation magnetic field interference component based on wavelet transform, frequency domain mapping, and time domain correction; for the measured geomagnetic field data on the acquired movement trajectory, obtain the geomagnetic background component by using the method in geomagnetic navigation based on the measured geomagnetic field data; for the acquired dynamic geomagnetic field data, extract the dynamic magnetic interference component generated by platform movement by using Fourier transform and filtering processing; subtract the geomagnetic background component, the daily variation magnetic field interference component, and the dynamic magnetic interference component generated by platform movement from the geomagnetic field data to obtain the measurement noise component; thereby obtaining each calibrated magnetic interference component.

[0031] Furthermore, it further includes a correction module, which is configured to subtract each calibrated magnetic interference component from the geomagnetic field data acquired by the magnetic sensor during the movement of the magnetic exploration platform to obtain the corrected geomagnetic field data.

[0032] Furthermore, in the magnetic interference component extraction module, the extraction of the daily variation magnetic field interference component by using wavelet transform, frequency domain mapping, and time domain correction includes:

[0033] For the static geomagnetic field data, apply the wavelet decomposition method to decompose the geomagnetic field signal into sub-band components of different scales, and further obtain the daily variation magnetic field interference component with high-frequency noise;

[0034] Perform Fourier transform on the daily variation magnetic field interference component with high-frequency noise to obtain the corresponding frequency domain mapping;

[0035] Filter the frequency domain mapping by using a low-pass filter to obtain a low-frequency component;

[0036] Perform an inverse Fourier transform on the filtered low-frequency component to obtain the daily-varying magnetic field interference component with high-frequency noise removed.

[0037] Further, the obtaining of the geomagnetic background component by using the method in geomagnetic navigation based on the measured geomagnetic field data in the magnetic interference component extraction module includes:

[0038] The measured geomagnetic field data on the movement trajectory includes continuous background geomagnetic field signals and local magnetic field disturbance signals;

[0039] Perform a smoothing process on the measured geomagnetic field data to obtain continuous background geomagnetic field signals;

[0040] Map the continuous background geomagnetic field signals to the entire ground measurement site through linear interpolation to construct a site background magnetic field model, and use the site background magnetic field model to obtain the geomagnetic background component; where the site background magnetic field model is:

[0041]

[0042] In the formula, n represents the number of trajectory points used in the interpolation; B bg (t i ) represents the geomagnetic background corresponding to time t i ; represents the distance between the point to be solved with weight p and trajectory point i or j, and the weight p is used to control the sensitivity to the change with distance; (x, y) represents the position coordinates of the measurement point.

[0043] Further, the extraction of the dynamic magnetic interference component generated by the movement of the extraction platform in the magnetic interference component extraction module includes:

[0044] Perform a fast Fourier transform on the collected dynamic geomagnetic field data to obtain a frequency-domain representation; where the frequency-domain representation of the dynamic geomagnetic field data includes a dynamic magnetic interference component and a DC geomagnetic field component;

[0045] Perform filtering on the frequency-domain representation of the dynamic geomagnetic field data to separate and obtain the frequency characteristics of the dynamic magnetic interference component;

[0046] Convolve the frequency characteristics of the dynamic magnetic interference component with a convolution kernel to obtain a convolution result; the convolution result is the dynamic magnetic interference component generated by the movement of the platform.

[0047] The beneficial technical effects of the present invention are:

[0048] The present invention provides a method and system for ground calibration of magnetic interference in an airborne magnetic exploration platform. An apparatus equipped with a magnetic sensor is placed in a ground environment without strong magnetic interference, and the magnetic sensor is used to collect geomagnetic field data. The geomagnetic field data includes a geomagnetic background component, a daily-varying magnetic field interference component, a dynamic magnetic interference component generated by the movement of the platform, and a measurement noise component. For the collected static geomagnetic field data, the daily-varying magnetic field interference component is extracted by using wavelet transform, frequency-domain mapping, and time-domain correction. A preset movement trajectory of the apparatus is set, and the apparatus is made to move along the preset trajectory, and the measured geomagnetic field data on this movement trajectory is recorded. Based on the measured geomagnetic field data, the geomagnetic background component is obtained by using a method in geomagnetic navigation. The apparatus is made to rotate slowly, and for the collected dynamic geomagnetic field data, the dynamic magnetic interference component generated by the movement of the platform is extracted by using Fourier transform and filtering processing. The measurement noise component is obtained by subtracting the geomagnetic background component, the daily-varying magnetic field interference component, and the dynamic magnetic interference component generated by the movement of the platform from the geomagnetic field data, thereby obtaining each calibrated magnetic interference component. Among them, the initial position is determined in a ground stationary environment and the magnetic sensor data is collected for calibration without hardware other than the magnetic sensor; the daily-varying magnetic field component is extracted by wavelet, and frequency-domain mapping and time-domain correction are performed to remove the influence of high-frequency noise, and the daily-varying magnetic field interference can be extracted more accurately; the magnetic map is measured and the background magnetic field is obtained according to the trajectory line by using a method in geomagnetic navigation, and a better modeling effect on the background magnetic field is achieved; the frequency characteristics of the dynamic interference are analyzed by Fourier transform, and a convolution operation is introduced to more accurately extract the key frequency characteristics in the signal, so as to realize the accurate extraction of the platform magnetic interference component. The present invention lays a foundation for subsequent flight data correction. Description of the Drawings

[0049] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present invention will become readily understood. In the drawings, several embodiments of the present invention are shown in an exemplary rather than restrictive manner, wherein:

[0050] Figure 1 is a flowchart of a method for ground calibration of magnetic interference in an airborne magnetic exploration platform according to an embodiment of the present invention.

[0051] Figure 2 is a schematic structural diagram of a system for ground calibration of magnetic interference in an airborne magnetic exploration platform according to an embodiment of the present invention. Detailed Embodiments

[0052] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided only to enable those skilled in the art to better understand and implement the present invention, and not to limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to be able to fully convey the scope of the present disclosure to those skilled in the art.

[0053] Those skilled in the art know that the embodiments of the present invention can be implemented as a system, a device, an equipment, a method, or a computer program product. Therefore, the present disclosure can be specifically implemented in the following forms, namely: entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software. In this article, it should be understood that any number of elements in the drawings is for illustration rather than limitation, and any naming is only for distinction and does not have any limiting meaning.

[0054] An embodiment of the present invention provides a method for calibrating magnetic interference on the ground of an airborne magnetic exploration platform, as Figure 1 shown, the method includes:

[0055] S1. Place the device equipped with a magnetic sensor in a ground environment without strong magnetic interference, and use the magnetic sensor to collect geomagnetic field data; the geomagnetic field data includes geomagnetic background components, daily variation magnetic field interference components, dynamic magnetic interference components generated by platform movement, and measurement noise components;

[0056] S2. For the collected static geomagnetic field data, use wavelet transform, frequency domain mapping, and time domain correction to extract the daily variation magnetic field interference components;

[0057] S3. Preset the device movement trajectory, make the device move along the preset trajectory, record the measured geomagnetic field data on this movement trajectory, and obtain the geomagnetic background components based on the measured geomagnetic field data using the method in geomagnetic navigation;

[0058] S4. Make the device rotate slowly. For the collected dynamic geomagnetic field data, use Fourier transform and filtering processing to extract the dynamic magnetic interference components generated by platform movement;

[0059] S5. Subtract the geomagnetic background components, daily variation magnetic field interference components, and dynamic magnetic interference components generated by platform movement from the geomagnetic field data to obtain the measurement noise components; thus, each calibrated magnetic interference component is obtained.

[0060] The method starts with S1. In S1, the device equipped with a magnetic sensor is placed in a ground environment without strong magnetic interference, and the magnetic sensor is used to collect geomagnetic field data.

[0061] According to an embodiment of the present invention, first, the ground initial position is determined and the magnetic sensor data is collected. The device equipped with the magnetic sensor is placed in a static ground environment, and an open area without strong external magnetic interference is selected as the calibration site to ensure that the device will not be interfered by environmental factors during the calibration process. Without moving the device, the magnetic sensor is used to collect the data in the X, Y, and Z axis directions of the geomagnetic field at a constant sampling rate f s Record multiple groups of magnetic field data in different directions. The original data recorded is: where M total is the total magnetic field measured by the sensor, M bg is the geomagnetic background component, is the diurnal magnetic field interference component, is the dynamic magnetic interference component generated by the platform movement, M noise is the measurement noise component.

[0062] Then, execute S2. In S2, for the collected static geomagnetic field data, the diurnal magnetic field interference component is extracted by using wavelet transform, frequency domain mapping, and time domain correction. Specifically, it includes: for the geomagnetic field data, the wavelet decomposition method is applied to decompose the geomagnetic field signal into sub-band components of different scales, and then the diurnal magnetic field interference component with high-frequency noise is obtained; the Fourier transform is performed on the diurnal magnetic field interference component with high-frequency noise to obtain the corresponding frequency domain mapping; the frequency domain mapping is filtered by a low-pass filter to obtain the low-frequency component; the inverse Fourier transform is performed on the filtered low-frequency component to obtain the diurnal magnetic field interference component with high-frequency noise removed.

[0063] According to an embodiment of the present invention, to separate the diurnal magnetic field interference component The wavelet decomposition method is applied to decompose the total magnetic field signal into sub-band components of different scales. The discrete wavelet transform of the signal is expressed as:

[0064]

[0065] where W j,k is the wavelet component coefficient, ψ j,k [n]=2 j / 2 ψ(2 j n-k) is the discrete form of the wavelet basis function, and j and k respectively represent the decomposition scale and the displacement parameter.

[0066] By selecting an appropriate wavelet basis and the number of decomposition layers, the diurnal low-frequency component can be extracted from the total magnetic field M total .

[0067] Furthermore, in order to effectively remove the noise interference in the above diurnal low-frequency component while retaining the main characteristics of the geomagnetic field reference signal, the frequency domain processing technology is used to correct the data.

[0068] Frequency domain mapping converts the signal D(t) in the time domain to the frequency domain. By analyzing its frequency components, the diurnal magnetic field and noise components are distinguished. Fourier transform is used to achieve the frequency domain mapping of the signal:

[0069]

[0070] Where is the signal representation in the frequency domain, f is the frequency, and D(t) is the signal in the time domain. In the frequency domain, the diurnal magnetic field is mainly concentrated in the lower frequency bands, while the high-frequency components are usually caused by random noise. Through frequency domain analysis, the distribution characteristics of different frequency components can be accurately identified. To remove the high-frequency noise and retain the low-frequency diurnal magnetic field signal, a low-pass filter is designed, and its frequency response function H(f) is defined as:

[0071]

[0072] Where f c is the cut-off frequency of the filter, which is selected considering the main frequency range of the geomagnetic diurnal variation. The filtered frequency domain signal is:

[0073]

[0074] In this way, the high-frequency noise is removed, and at the same time, the main components of the diurnal magnetic field are retained. The filtered signal is restored from the frequency domain to the time domain to recover the corrected diurnal magnetic field signal D corrected (t), and this process is achieved through the inverse Fourier transform:

[0075]

[0076] The restored D corrected (t) is the signal from which the high-frequency noise has been removed and can more accurately reflect the true variation of the diurnal magnetic field. The restored D corrected (t) is reassigned to That is, the calibrated diurnal magnetic field interference component is obtained.

[0077] Then, S3 is executed. In S3, a preset device movement trajectory is set, and the device is made to move along the preset trajectory. The measured geomagnetic field data on this movement trajectory is recorded, and the geomagnetic background component is obtained based on the measured geomagnetic field data using the method in geomagnetic navigation. Specifically, the measured geomagnetic field data includes continuous background geomagnetic field signals and local magnetic field perturbation signals; the measured geomagnetic field data is smoothed to obtain continuous background geomagnetic field signals; the continuous background geomagnetic field signals are mapped to the entire ground measurement site through linear interpolation to construct a site background magnetic field model, so as to obtain the geomagnetic background component using the site background magnetic field model.

[0078] According to an embodiment of the present invention, the data collected by the magnetic sensor in the X, Y, and Z axis directions of the geomagnetic field are as follows:

[0079] B(x,y) = {B X (x,y), B Y (x,y), B Z (x,y)}

[0080] where (x,y) are the coordinates of the measurement position, and B Z (x,y) is the magnetic field component in the vertical direction. By analyzing the collected magnetic map data, the spatial distribution characteristics of the magnetic field are revealed, including the background component M bg of the natural geomagnetic field and the gradient changes caused by local interference sources.

[0081] Then, through the method in geomagnetic navigation, the background magnetic field is extracted from the magnetic map according to the measured trajectory line. Assuming that the navigation device moves along the known trajectory r(t) = (x(t), y(t)), the sensor continuously records the magnetic field data B measured (t) on the trajectory. At this time, the measured magnetic field data contains the background magnetic field B bg and the local magnetic field perturbation B dist , and their relationship is:

[0082] B measured (t) = B bg (t) + B dist (t)

[0083] The background magnetic field is usually a low-frequency signal that changes slowly with space, while the interference components are mostly local mutations or high-frequency components. By smoothing the magnetic field data B measured (t) on the trajectory line, the smooth background magnetic field B bg (t) can be extracted:

[0084] B bg (t) = L{B measured (t)}

[0085] where L represents the smoothing operation. After the background magnetic field on the trajectory line is extracted, it is mapped to the entire measurement site through linear interpolation to construct the site background magnetic field model M bg (x,y):

[0086]

[0087] In the formula, n represents the number of trajectory points used in the interpolation; B bg (t i ) represents the geomagnetic background corresponding to time t i ; Denote the distance between the point to be solved with weight p and the trajectory point i or j, and the weight p is used to control the sensitivity to the distance change.

[0088] Then execute S4. In S4, make the device rotate slowly. For the collected dynamic geomagnetic field data, use Fourier transform and filtering processing to extract the dynamic magnetic interference component generated by the platform movement; specifically include: perform fast Fourier transform on the collected dynamic geomagnetic field data to obtain the frequency domain representation; wherein, the frequency domain representation of the dynamic geomagnetic field data includes the dynamic magnetic interference component and the DC geomagnetic field component; filter the frequency domain representation of the dynamic geomagnetic field data to separate and obtain the frequency characteristics of the dynamic magnetic interference component; convolve the frequency characteristics of the dynamic magnetic interference component with a convolution kernel to obtain a convolution result; the convolution result is the dynamic magnetic interference component generated by the platform movement.

[0089] According to the embodiment of the present invention, place the device in a slowly rotating state to simulate the magnetic field change in a dynamic environment, and at the same time collect the magnetic sensor data. The rotation is achieved by controlling the rate of the platform turntable. For the collected magnetic field data M total Perform fast Fourier transform to obtain the frequency domain representation:

[0090] M total (f)=F{M total (t)}

[0091] where f is the frequency and M total (f) is the spectrum of the total magnetic field. In this frequency domain representation, the total magnetic field M total (f) can be decomposed into dynamic interference and the geomagnetic field M geo , the dynamic interference usually contains components with lower frequencies, while the geomagnetic field M geo appears as a DC component in the frequency domain. Separate the frequency characteristics of the dynamic interference through filtering and decompose the time characteristics of the dynamic interference:

[0092]

[0093] where a i and b i are the amplitudes of the components of the dynamic interference, w i is the angular frequency of the components of the dynamic interference, and N is the number of frequency components.

[0094] On the basis of analyzing , introduce a convolution operation to more accurately extract the key frequency characteristics in the signal. Convolve with a selected 3*3 convolution kernel h(t) to obtain a convolution result M conv (t):

[0095]

[0096] where h(t) is the convolution kernel, which is used to extract or filter the frequency components of dynamic interference, and a high-pass filtering kernel is selected; M conv (t) is the signal after convolution processing. Through the convolution operation, the dynamic interference signal is separated into specific frequency components or time-local feature components. For frequency component extraction, the Fourier transform can be combined to obtain the spectral characteristics after convolution processing:

[0097]

[0098] where H(f) is the frequency response function of the convolution kernel. By multiplying it with the frequency characteristics of the signal , the signal separation or interference suppression in the frequency domain can be effectively achieved.

[0099] Then, S5 is executed. In S5, the geomagnetic field data is subtracted by the geomagnetic background component, the daily variation magnetic field interference component, and the dynamic magnetic interference component generated by the platform movement to obtain the measurement noise component; thus, each calibrated magnetic interference component is obtained.

[0100] Further, after the calibration is completed, the calibration effect is verified by comparing with the known geomagnetic field standard value. If the calibration error is within the allowable range, it indicates that the platform magnetic interference calibration is successful; otherwise, the modeling and calibration need to be carried out again. To improve the accuracy and robustness of the calibration, calibration can be selected at two different site environments, and the magnetic field data in different environments can be combined to correct the model to achieve adaptive adjustment to cope with magnetic interference in different scenarios.

[0101] In this embodiment, preferably, after S5, S6 is further included. In S6, the geomagnetic field data collected by the magnetic sensor during the movement of the magnetic exploration platform is subtracted by each calibrated magnetic interference component to obtain the corrected geomagnetic field data.

[0102] Specifically, after the calibration is completed, the magnetic interference terms of the platform are known. According to the platform magnetic interference model (each calibrated magnetic interference component), the magnetic field data output by the magnetic sensor is corrected in real time. Whenever the device is in motion and the magnetic sensor detects a magnetic field change, the interference value in the platform magnetic interference model is subtracted from the detected data to obtain a more accurate geomagnetic field data. Assuming the data collected in real time is then the corrected geomagnetic field data is:

[0103]

[0104] According to the above calibration method, the magnetic interference of the platform can be removed to obtain more accurate geomagnetic field information.

[0105] Another embodiment of the present invention provides a magnetic interference ground calibration system for an airborne magnetic exploration platform, as Figure 2 shown. The system includes:

[0106] A geomagnetic data acquisition module 210, which is configured to place a device equipped with a magnetic sensor in a ground environment without strong magnetic interference, use the magnetic sensor to collect static geomagnetic field data; preset a device movement trajectory, make the device move along the preset trajectory, and use the magnetic sensor to collect measured geomagnetic field data on the movement trajectory; make the device rotate slowly, and use the magnetic sensor to collect dynamic geomagnetic field data; the geomagnetic field data includes a geomagnetic background component, a daily variation magnetic field interference component, a dynamic magnetic interference component generated by platform movement, and a measurement noise component;

[0107] A magnetic interference component extraction module 220, which is configured to, for the collected static geomagnetic field data, use wavelet transform, frequency domain mapping, and time domain correction to extract the daily variation magnetic field interference component; for the measured geomagnetic field data on the movement trajectory, obtain the geomagnetic background component based on the measured geomagnetic field data by using the method in geomagnetic navigation; for the collected dynamic geomagnetic field data, use Fourier transform and filtering processing to extract the dynamic magnetic interference component generated by platform movement; subtract the geomagnetic background component, the daily variation magnetic field interference component, and the dynamic magnetic interference component generated by platform movement from the geomagnetic field data to obtain the measurement noise component; thus obtaining each calibrated magnetic interference component.

[0108] In this embodiment, optionally, it further includes a correction module 230, which is configured to subtract each calibrated magnetic interference component from the geomagnetic field data collected by the magnetic sensor during the movement of the magnetic exploration platform to obtain the corrected geomagnetic field data.

[0109] In this embodiment, optionally, the extraction of the daily variation magnetic field interference component by using wavelet transform, frequency domain mapping, and time domain correction in the magnetic interference component extraction module 220 includes:

[0110] For the static geomagnetic field data, apply the wavelet decomposition method to decompose the geomagnetic field signal into sub-band components of different scales, and then obtain the daily variation magnetic field interference component with high-frequency noise;

[0111] Perform Fourier transform on the daily variation magnetic field interference component with high-frequency noise to obtain the corresponding frequency domain mapping;

[0112] Use a low-pass filter to filter the frequency domain mapping to obtain a low-frequency component;

[0113] Perform inverse Fourier transform on the filtered low-frequency component to obtain the daily variation magnetic field interference component with high-frequency noise removed.

[0114] In this embodiment, optionally, the obtaining of the geomagnetic background component by using the method in geomagnetic navigation based on the measured geomagnetic field data in the magnetic interference component extraction module 220 includes:

[0115] The measured geomagnetic field data includes a continuous background geomagnetic field signal and a local magnetic field perturbation signal;

[0116] Perform smoothing processing on the measured geomagnetic field data to obtain a continuous background geomagnetic field signal;

[0117] Map the continuous background geomagnetic field signal to the entire ground measurement site through linear interpolation to construct a site background magnetic field model, so as to obtain the geomagnetic background component by using the site background magnetic field model; where the site background magnetic field model is:

[0118]

[0119] In the formula, n represents the number of trajectory points used in the interpolation; B bg (t i ) represents the geomagnetic background corresponding to time t i ; represents the distance between the point to be solved with weight p and the trajectory point i or j, and the weight p is used to control the sensitivity to the change with distance; (x, y) represents the position coordinates of the measurement point.

[0120] In this embodiment, optionally, the extraction of the dynamic magnetic interference component generated by the movement of the platform in the magnetic interference component extraction module 220 includes:

[0121] Perform a fast Fourier transform on the collected dynamic geomagnetic field data to obtain a frequency domain representation; where the frequency domain representation of the dynamic geomagnetic field data includes a dynamic magnetic interference component and a DC geomagnetic field component;

[0122] Filter the frequency domain representation of the dynamic geomagnetic field data to separate and obtain the frequency characteristics of the dynamic magnetic interference component;

[0123] Convolve the frequency characteristics of the dynamic magnetic interference component with a convolution kernel to obtain a convolution result; the convolution result is the dynamic magnetic interference component generated by the movement of the platform.

[0124] It should be noted that the functions of the magnetic interference ground calibration system for an airborne magnetic exploration platform in this embodiment can be described by the foregoing magnetic interference ground calibration method for an airborne magnetic exploration platform. For the parts not detailed in the system embodiment, please refer to the above method embodiment.

[0125] It should be noted that although several units, modules or sub-modules are mentioned in the above detailed description, this division is merely exemplary and not mandatory. In fact, according to the embodiments of the present invention, the features and functions of two or more of the above-described modules can be embodied in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0126] In addition, although the operations of the method of the present invention are described in a specific order in the drawings, this does not require or imply that these operations must be performed in that specific order, or that all of the shown operations must be performed to achieve the desired result. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may be decomposed into multiple steps for execution.

[0127] Although the spirit and principles of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the division of each aspect does not mean that the features in these aspects cannot be combined for benefit. This division is only for the convenience of expression. The present invention aims to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for ground calibration of magnetic interference of an airborne magnetic exploration platform, characterized in that, Comprising: Placing a device equipped with a magnetic sensor in a ground environment without strong magnetic interference, and collecting geomagnetic field data using the magnetic sensor; the geomagnetic field data includes a geomagnetic background component, a diurnal magnetic field interference component, a dynamic magnetic interference component generated by platform movement, and a measurement noise component; For the collected static geomagnetic field data, using wavelet transform, frequency domain mapping, and time domain correction to extract the diurnal magnetic field interference component; Presetting a device movement trajectory, making the device move along the preset trajectory, recording the measured geomagnetic field data on this movement trajectory, and obtaining the geomagnetic background component based on the measured geomagnetic field data using the method in geomagnetic navigation; Making the device rotate slowly, and for the collected dynamic geomagnetic field data, using Fourier transform and filtering processing to extract the dynamic magnetic interference component generated by platform movement; Subtracting the geomagnetic background component, the diurnal magnetic field interference component, and the dynamic magnetic interference component generated by platform movement from the geomagnetic field data to obtain the measurement noise component; thus obtaining each calibrated magnetic interference component.

2. A method for ground calibration of magnetic interference of an airborne magnetic exploration platform according to claim 1, characterized in that, Subtracting each calibrated magnetic interference component from the geomagnetic field data collected by the magnetic sensor during the movement of the magnetic exploration platform to obtain the corrected geomagnetic field data.

3. A method for ground calibration of magnetic interference of an airborne magnetic exploration platform according to claim 1 or 2, characterized in that, The using wavelet transform, frequency domain mapping, and time domain correction to extract the diurnal magnetic field interference component includes: For the static geomagnetic field data, applying the wavelet decomposition method to decompose the geomagnetic field signal into sub-band components of different scales, and further obtaining the diurnal magnetic field interference component with high-frequency noise; Performing Fourier transform on the diurnal magnetic field interference component with high-frequency noise to obtain the corresponding frequency domain mapping; Filtering the frequency domain mapping using a low-pass filter to obtain a low-frequency component; Performing inverse Fourier transform on the filtered low-frequency component to obtain the diurnal magnetic field interference component with high-frequency noise removed.

4. A method for ground calibration of magnetic interference of an airborne magnetic exploration platform according to claim 1 or 2, characterized in that, The obtaining the geomagnetic background component based on the measured geomagnetic field data using the method in geomagnetic navigation includes: the measured geomagnetic field data includes a continuous background geomagnetic field signal and a local magnetic field perturbation signal; Performing smoothing processing on the measured geomagnetic field data to obtain the continuous background geomagnetic field signal; Mapping the continuous background geomagnetic field signal to the entire ground measurement site through linear interpolation method to construct a site background magnetic field model, so as to obtain the geomagnetic background component using the site background magnetic field model; wherein, the site background magnetic field model is: Where n represents the number of trajectory points used in interpolation; B bg (t i ) represents the geomagnetic background corresponding to time t i ; represents the distance between the point to be determined with weight p and trajectory point i or j, where the weight p is used to control the sensitivity to distance changes; (x, y) represents the position coordinates of the measurement point.

5. A method for ground calibration of magnetic interference of an airborne magnetic exploration platform according to claim 1 or 2, characterized in that, The using Fourier transform and filtering processing to extract the dynamic magnetic interference component generated by platform movement includes: Performing fast Fourier transform on the collected dynamic geomagnetic field data to obtain a frequency domain representation; wherein, the frequency domain representation of the dynamic geomagnetic field data includes a dynamic magnetic interference component and a DC geomagnetic field component; Filtering the frequency domain representation of the dynamic geomagnetic field data to separate and obtain the frequency characteristics of the dynamic magnetic interference component; Convolving the frequency characteristics of the dynamic magnetic interference component with a convolution kernel to obtain a convolution result; the convolution result is the dynamic magnetic interference component generated by platform movement.

6. A method for calibrating magnetic interference on the ground of an airborne magnetic exploration platform according to claim 5, characterized in that, The convolution kernel is a high-pass filter kernel.

7. An airborne magnetic exploration platform magnetic interference ground calibration system, characterized in that, Comprising: The geomagnetic data acquisition module is configured to place a device equipped with a magnetic sensor in a ground environment without strong magnetic interference, and use the magnetic sensor to collect static geomagnetic field data; preset the movement trajectory of the device, enable the device to move along the preset trajectory, and use the magnetic sensor to collect the measured geomagnetic field data on the movement trajectory; enable the device to rotate slowly, and use the magnetic sensor to collect dynamic geomagnetic field data; the geomagnetic field data includes a geomagnetic background component, a daily-varying magnetic field interference component, a dynamic magnetic interference component generated by platform movement, and a measurement noise component; The magnetic interference component extraction module is configured to, for the collected static geomagnetic field data, extract the daily-varying magnetic field interference component by using wavelet transform, frequency-domain mapping, and time-domain correction; for the measured geomagnetic field data on the movement trajectory, obtain the geomagnetic background component based on the measured geomagnetic field data by using the method in geomagnetic navigation; for the collected dynamic geomagnetic field data, extract the dynamic magnetic interference component generated by platform movement by using Fourier transform and filtering processing; subtract the geomagnetic background component, the daily-varying magnetic field interference component, and the dynamic magnetic interference component generated by platform movement from the geomagnetic field data to obtain the measurement noise component; thus, obtain each calibrated magnetic interference component.

8. A ground calibration system for magnetic interference of an airborne magnetic exploration platform according to claim 7, characterized in that, It further includes a correction module, which is configured to subtract each calibrated magnetic interference component from the geomagnetic field data collected by the magnetic sensor during the movement of the magnetic exploration platform to obtain the corrected geomagnetic field data.

9. An airborne magnetic exploration platform magnetic interference ground calibration system according to claim 7 or 8, characterized in that The extraction of the daily-varying magnetic field interference component by using wavelet transform, frequency-domain mapping, and time-domain correction in the magnetic interference component extraction module includes: For the static geomagnetic field data, apply the wavelet decomposition method to decompose the geomagnetic field signal into sub-band components of different scales, and further obtain the daily-varying magnetic field interference component with high-frequency noise; Perform Fourier transform on the daily-varying magnetic field interference component with high-frequency noise to obtain the corresponding frequency-domain mapping; Filter the frequency-domain mapping by using a low-pass filter to obtain the low-frequency component; Perform inverse Fourier transform on the filtered low-frequency component to obtain the daily-varying magnetic field interference component with high-frequency noise removed.

10. A magnetic interference ground calibration system for an airborne magnetic exploration platform according to claim 7 or 8, characterized in that, The obtaining of the geomagnetic background component based on the measured geomagnetic field data by using the method in geomagnetic navigation in the magnetic interference component extraction module includes: The measured geomagnetic field data includes a continuous background geomagnetic field signal and a local magnetic field perturbation signal; Perform smoothing processing on the measured geomagnetic field data to obtain the continuous background geomagnetic field signal; Map the continuous background geomagnetic field signal to the entire ground measurement site by using the linear interpolation method to construct a site background magnetic field model, so as to obtain the geomagnetic background component by using the site background magnetic field model; where the site background magnetic field model is: where n represents the number of trajectory points used in interpolation; B bg (t i ) represents the geomagnetic background corresponding to time t i ; represents the distance between the point to be solved with weight p and trajectory point i or j, and the weight p is used to control the sensitivity to distance variation; (x, y) represents the position coordinates of the measurement point; The extraction of the dynamic magnetic interference component generated by platform movement by using Fourier transform and filtering processing includes: Perform fast Fourier transform on the collected dynamic geomagnetic field data to obtain the frequency-domain representation; where the frequency-domain representation of the dynamic geomagnetic field data includes a dynamic magnetic interference component and a DC geomagnetic field component; Filter the frequency-domain representation of the dynamic geomagnetic field data to separate and obtain the frequency characteristics of the dynamic magnetic interference component; Convolve the frequency characteristics of the dynamic magnetic interference component with a convolution kernel to obtain a convolution result; the convolution result is the dynamic magnetic interference component generated by the platform movement.

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