Magnetic diurnal correction method for survey geomagnetic vector measurement

Abstract

To provide a magnetic diurnal variation correction method of geomagnetic vector measurement for exploration related to a magnetic exploration technical field of geophysical exploration.SOLUTION: The present invention includes two parts, i.e., an outdoor observation stage and an indoor calculation stage, the outdoor observation stage is divided into two parts, i.e., a magnetic vector measurement of a solar station and a magnetic vector measurement of a mobile station, a device used by the solar station is mainly a general-purpose high-precision 3-axis flux gate magnetometer body 1, and a device used by the mobile station is mainly a general-purpose high-precision 3-axis flux gate magnetometer body 2 and a high-precision attitude meter body. The daily change correction method for magnetic vector measurement according to the present invention does not need to use equipment such as a theodolite, does not need to accurately orient a magnetic probe, and can realize daily change correction by placing the magnetometer main body 2 and the magnetometer main body 1 at a daily change station observation point and performing simultaneous observation at the same location twice to convert magnetic three component data observed at the daily change station into the same geographic coordinate system as that of a moving station.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to the technical field of magnetic exploration for geophysical exploration, and more particularly to a method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration. [Background technology]

[0002] Geophysical exploration technology involves many fields such as gravity, magnetism, electricity, and seismology, among which magnetic exploration has a long history, is simple and easy to implement, and can achieve data collection in a variety of scenes such as air, sky, earth, wells, and underwater, and various measurement modes can be adopted, such as total field measurement, total field gradient measurement, three-component measurement, three-component gradient measurement, and orientation measurement (vertical component). In recent years, with the advancement of exploration technology, aeromagnetic vector measurement has attracted more and more attention from the industry, and research into each technological stage of magnetic vector measurement has become increasingly in-depth, and high-precision three-axis flux gate magnetometers have also been rapidly popularized and applied.

[0003] In geophysical exploration, magnetic surveys using magnetometers are the most cost-effective and rapid method, and accurate field observation of magnetic vector parameters has been a long-standing research goal. Magnetic vector parameters include the strength (amplitude) and direction of the total magnetic field, which can also be expressed as three magnetic components in a geographic coordinate system (i.e., the X component corresponding to geographic north, the Y component corresponding to geographic east, and the Z component corresponding to vertically downward). Currently, field observations are often performed using a three-axis flux-gate magnetometer. That is, a magnetometer with three orthogonal magnetic axes is used to observe the three orthogonal direction components of the total magnetic field, and then the strength and direction of the total magnetic field are calculated by combining them.

[0004] Magnetic surveys are subject to interference from diurnal magnetic variation, which refers to short-term changes in the magnetic field caused by geomagnetic perturbations and cosmic magnetic storms. These variations change over time and can reach tens of nadir. Magnetic surveys must take corrective measures to address the diurnal magnetic variation issue, known as diurnal magnetic variation correction. Whether using the total magnetic field (scalar) survey mode or the magnetic vector survey mode, diurnal magnetic variation correction is necessary, but the method for correcting diurnal magnetic variation in the magnetic vector survey mode is more complex and difficult. The conventional background art of diurnal variation correction in magnetic vector surveying relates to the following problems.

[0005] 1. The geomagnetic field in the field work area changes over time, but these changes are consistent over an area of ​​several hundred square kilometers. Therefore, a diurnal variation observation mode can be used to correct for this. A quiet location near the work area with a mild magnetic field and no human interference is selected as the observation point for the diurnal variation station. Continuous static observations are performed at the diurnal variation station using a magnetometer, and the magnetic field values ​​are recorded. This allows the magnetic field values ​​at different times in the same location, i.e., the temporal change in the geomagnetic field, to be measured. Using this as a basis, under time-synchronized conditions, the magnetic field values ​​measured at the mobile station in the measurement network are subtracted from the temporal change in the magnetic field at that measurement time to achieve magnetic diurnal variation correction.

[0006] 2. Unlike diurnal variation correction in total magnetic field (scalar) surveying, diurnal variation correction in magnetic vector surveying requires measuring not only the amplitude of diurnal magnetic variation but also the azimuth change of the diurnal magnetic variation. Currently, field observations of diurnal variation are primarily performed using three-axis flux gate magnetometers to measure the three components of the magnetic field. To match the three observed components of the magnetic field to the three components of the geographic coordinate system, the current method uses equipment such as a magnetic-free theodolite. The three-axis flux gate magnetometer probe is fixed on the theodolite and aligned with the X-Y-Z magnetic axes indicated by the probe. The probe case is used as the reference point, and a distant feature is used as the reference point. The front of the theodolite is aligned with this reference point, determining that the X magnetic axis (case face) of the magnetic probe is pointing toward geographic north. When the theodolite turntable is leveled, the X-Y coordinate plane of the probe is determined to be horizontal, and the X-Y-Z magnetic axes of the magnetic probe are determined to correspond to the north-east-downward direction in the geographic coordinate system. The magnetic measurement three-component data of the magnetic measurement mobile station can be converted into XYZ magnetic three-component data in the geographic coordinate system based on the attitude sensor data, thereby ensuring that the coordinate systems of the diurnal variation station's magnetic three-component and the mobile station's magnetic three-component are consistent, and realizing diurnal variation correction of magnetic vector measurement under observation time synchronization.

[0007] 3. The problems with the diurnal variation correction mode of magnetic vector surveying are as follows: First, the XYZ magnetic axes of the magnetic probe are sealed inside the case, making it impossible to ensure that the magnetic axes are precisely parallel or perpendicular to the case. Therefore, in the theodolite geographic north mode, it is impossible to ensure that the X magnetic axis accurately points north, and therefore the azimuth accuracy cannot be determined. Similarly, it is impossible to ensure that the Y magnetic axis accurately points east, and it is impossible to ensure that the Z magnetic axis accurately points vertically downward. This azimuth deviation results in a large error (tens to hundreds of nT) in the diurnal variation correction of the magnetic vector. Second, the diurnal variation station uses a theodolite for orientation, and the mobile station uses an attitude sensor to determine its attitude (a built-in GNSS system can constantly measure the azimuth, pitch, and roll angles of the mobile station's magnetic probe). There are unavoidable system differences between the two modes, which cannot be accurately corrected, resulting in a significant reduction in the accuracy of the diurnal variation correction results of the magnetic vector. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration. The diurnal variation correction method for magnetic vector surveying of the present invention does not require the use of equipment such as a theodolite, nor does it require accurate orientation of the magnetic probe. Instead, magnetometer body 2 and magnetometer body 1 are simply placed at the diurnal variation station observation point and perform two simultaneous observations at the same location. The diurnal variation correction can be achieved by converting the three-component magnetic data observed at the diurnal variation station into the same geographic coordinate system as the mobile station. This method is simple, significantly improves accuracy, and enables quality control, thereby solving the problems raised in the background art mentioned above. [Means for solving the problem]

[0009] To achieve the above object, the present invention provides the following technical solutions: A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration, which includes two parts: a field observation step and an indoor calculation step,

[0010] The field observation stage is divided into two parts: a diurnal variation station magnetic vector measurement and a mobile station magnetic vector measurement. The diurnal variation station magnetic vector measurement uses a diurnal variation station measurement device, and the equipment used at the diurnal variation station is mainly a general-purpose high-precision three-axis magnetic flux gate magnetometer body 1. The mobile station magnetic vector measurement uses a field mobile measurement device, and the equipment used at the mobile station is mainly a general-purpose high-precision three-axis magnetic flux gate magnetometer body 2 and a high-precision attitude meter body.

[0011] The day-changing station measuring device is composed of a magnetometer main body 1, a magnetometer probe, and a probe holder, and the field mobile measuring device is composed of a magnetometer main body 2, an attitude meter main body, a three-component magnetic probe, an attitude meter forward positioning antenna, an attitude meter rearward positioning antenna, a T-shaped pipe shelf, and a pipe shelf fixing cable.

[0012] Furthermore, the magnetic three-component data observed in the survey network by the mobile station is converted into magnetic three-component data in a geographic coordinate system based on the attitude sensor body data.

[0013] Furthermore, the diurnal variation station uses the static continuous observation mode of the three-axis flux gate magnetometer main body 1 to measure the three magnetic field components at different times in the same location, and during the field observation stage, a mobile station must be set up at the diurnal variation station twice a day, in the morning and in the afternoon, to perform continuous observations synchronously with the diurnal variation station at the same location.

[0014] Furthermore, the three-component magnetic probe of the mobile station is approximately 50 cm away from the magnetometer probe of the diurnal variation station, and the two are at the same height. Using observation data from two periods, the three-component magnetic field values ​​observed at the diurnal variation station at different times are converted into three magnetic field components in the same geographic coordinate system as the mobile station, thereby achieving vector correction of the diurnal magnetic variation in a time-synchronized manner. Furthermore, the field observation step includes:

[0015] A quiet place with a mild magnetic field and no interference near the work area is selected as the observation site for the diurnal variation station. The three-axis flux gate magnetometer probe is stably installed on the probe holder, and the three axes of the magnetometer probe (Mx, My, Mz) are approximately oriented geographically north, east, and vertically downward, respectively, and are not allowed to move. Before construction, the power is turned on to perform automatic continuous observation, and the time and magnetic measurement data are saved. The sampling frequency is step S1, which is higher than 1 Hz.

[0016] During the construction period, in the morning and afternoon or afternoon and evening, the magnetic measurement mobile station is transported to the diurnal variation station twice, the three-component magnetic probe is stably installed on the T-shaped pipe shelf, the T-shaped pipe shelf of the mobile station is installed near the magnetometer probe of the diurnal variation station, the three axes Mx, My, Mz of the three-component magnetic probe of the mobile station are roughly oriented geographically north, east, and vertically downward, respectively, and the mobile station is kept stationary. The power is turned on to perform automatic continuous observation, and the time and magnetic measurement data are stored. The sampling frequency is the same as that of the diurnal variation station, and the sampling time can be 1 to 3 minutes. Step S2.

[0017] Step S3: In addition to conducting the above-mentioned synchronous observation, the mobile station is also used to conduct magnetic vector observation in the measurement network during other periods, and stores observation point, time, attitude and magnetic vector data, which are used to calculate the observation time and magnetic three-component data of each observation point at geographic coordinates; Step S4: The magnetometer main body 1(1) of the day-changing station continuously observes and records at a predetermined sampling frequency during operation of the mobile station; Includes. Furthermore, the indoor calculation step

[0018] Step S5: Analyze the observation data of the first period when the magnetic measurement mobile station is near the diurnal variation station, create a diurnal variation curve graph, select a smooth flat section of the curve, compare it with the diurnal variation curve of the magnetic measurement data of the diurnal variation station during the same period, and if the shapes of the two curves are consistent and stable and flat, select the magnetic three-component data of the diurnal variation station and the magnetic three-component data of the mobile station at a certain time as the original inspection parameters of the first period for calculating the coordinate transformation coefficients;

[0019] Step S6: converting the magnetic three-component data of the mobile station at the selected specific time of the first period into magnetic three-component data in a geographic coordinate system based on the attitude sensor data at the same time;

[0020] Three-component magnetic data of the diurnal variation station at the specific time x mt1o , y mt1o , z mt1o , the three-component magnetic data of the mobile station in the geographic coordinate system x t1o , y t1o , z t1o and are normalized and scaled to a unit vector, and the processed three-component magnetic data x mt1 , y mt1 , z mt1 and the three-component magnetic data x of the mobile station in the geographic coordinate system. t1 , y t1 , z t1 Step S7 is as follows:

[0021]

number

[0022] The magnetic measurement mobile station analyzes the observation data of the second period when the magnetic measurement mobile station is near the diurnal variation station and the observation data of the diurnal variation station during the second period, and repeats the above steps S1, S2, and S3 to calculate the correction coefficient. mt2 , y mt2 , z mt2 , xt2 , y t2 , z t2 Step S8 to obtain The coordinate transformation coefficient matrix M is calculated using the following steps:

[0023]

number

[0024]

number

[0025]

number

[0026] Step S9: converting the three magnetic component values ​​measured at each time of the diurnal variation station into three magnetic component values ​​in a geographic coordinate system using matrix M; Correction for diurnal variation is performed using the coordinate transformation coefficient matrix M,

[0027]

number

[0028] where X mto , Y mto , Z mto are the three component values ​​of the original magnetic measurement data of the diurnal variation station at a certain time (t), and X to , Y to , Z to is the X mto , Y mto , Z mto are the three magnetic component values ​​converted into the geographic coordinate system. When correcting for diurnal variation, the magnetic vector data measured at the mobile station at the relevant time (t) is converted into X in the geographic coordinate system. tn , Y tn , Z tn Then, the three magnetic components in the geographic coordinate system are converted into X to , Y to , Z toThat is,

[0029]

number

[0030] X t , Y t , Z t are the three magnetic component values ​​after diurnal variation correction of the three magnetic component data measured at the mobile station at that time (t), which correspond to the geographic coordinate system, and include step S10 in which the diurnal variation correction work of the magnetic vector is completed by processing all observation times in the above manner. [Effects of the Invention]

[0031] Compared with the prior art, the present invention has the following beneficial effects.

[0032] 1. The magnetic diurnal variation correction method for measuring geomagnetic vectors for exploration of the present invention has higher applicability than other correction methods, can greatly improve the correction accuracy, and can improve the reliability of the correction results.

[0033] 2. The magnetic diurnal variation correction method for geomagnetic vector measurement for exploration of the present invention does not require the use of orientation equipment such as theodolite, is not affected by orientation errors, is easy to perform field observation, is less susceptible to other surrounding interference, and has a more stable correction effect.

[0034] 3. The method of correcting diurnal magnetic variation in geomagnetic vector measurement for exploration of the present invention has advantages in terms of coordinate system transformation. It is completely unaffected by the orientation error of the magnetic probe case, and can perfectly transform the magnetic three-component data measured at the diurnal variation station into the same geographic coordinate system as the mobile station. This ensures the accurate requirements for the direction of diurnal magnetic vector correction, and ensures the consistency and reliability of the results of diurnal magnetic vector correction for multi-day and multi-period magnetic measurements. [Brief explanation of the drawings]

[0035] [Figure 1]FIG. 1 is a schematic diagram of the configuration of a field mobile measuring device for measuring geomagnetic vectors according to the present invention. [Figure 2] FIG. 2 is a schematic diagram of the geomagnetic vector measuring station measuring device of the present invention. [Figure 3] FIG. 3 is a schematic diagram of a mobile station measuring device of the present invention. [Figure 4] FIG. 4 is a graph of the diurnal variation observation data of three magnetic components from the diurnal variation station of the present invention. [Figure 5] FIG. 5 is a graph of diurnal station magnetic diurnal variation data converted to the geographic coordinate system of the present invention. [Figure 6] FIG. 6 is a graph of the three magnetic component data of a mobile station before the diurnal variation correction of the present invention. [Figure 7] FIG. 7 is a graph of the three magnetic component data of a mobile station after the diurnal variation correction of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] The technical solutions in the embodiments of the present invention will be described below clearly and completely with reference to the drawings in the embodiments of the present invention, but it is clear that the described embodiments are only a part of the embodiments of the present invention and do not represent all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any inventive ideas fall within the protection scope of the present invention.

[0037] In order to improve the correction accuracy of the prior art and solve the problems of the large demand for field equipment and the complicated field process, the present embodiment puts forward the following technical solution with reference to FIGS. 1 to 7.

[0038] A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration, which includes two parts: a field observation step and an indoor calculation step, The field observation phase is divided into two parts: day-varying station magnetic vector measurement and mobile station magnetic vector measurement. For day-varying station magnetic vector measurement, a day-varying station measurement device is used, and the equipment used for the day-varying station is mainly a general-purpose high-precision three-axis flux gate magnetometer body 1 (1). For mobile station magnetic vector measurement, a field mobile measurement device is used, and the equipment used for the mobile station is mainly a general-purpose high-precision three-axis flux gate magnetometer body 2 (4) and a high-precision attitude sensor body (5). The attitude sensor body (5) can observe the azimuth angle, roll angle, and pitch angle of the three-component magnetic probe (6).

[0039] The day-change station measurement device is composed of a magnetometer main body 1 (1), a magnetometer probe (2), and a probe holder (3), and the magnetometer main body 1 (1) and the magnetometer probe (2) are connected by a connecting cable. The field mobile measurement device is composed of a magnetometer main body 2 (4), an attitude meter main body (5), a three-component magnetic probe (6), an attitude meter forward positioning antenna (7), an attitude meter rearward positioning antenna (8), a T-shaped pipe shelf (9), and a pipe shelf fixing cable (10), and the magnetometer main body 2 (4) and the three-component magnetic probe (6) are connected by a connecting cable, and the attitude meter main body (5) and the attitude meter forward positioning antenna (7) and the attitude meter rearward positioning antenna (8) are connected by connecting cables, respectively.

[0040] The three-component magnetic data observed in the survey network by the mobile station are converted into three-component magnetic data in a geographic coordinate system (X is geographic north, Y is geographic east, and Z is vertically downward) based on the data from the attitude sensor (there are many related technical documents, but they do not fall within the scope of protection of this invention, so they will not be mentioned here). The diurnal variation station uses the static continuous observation mode of the three-axis flux gate magnetometer main body 1 (1) to measure the three-component magnetic field values ​​at the same location but at different times. During the field observation phase, the mobile station is installed at the diurnal variation station twice a day, in the morning and in the afternoon, to perform synchronous continuous observations with the diurnal variation station. The three-component magnetic probe (6) of the mobile station is approximately 50 cm away from the magnetometer probe (2) of the diurnal variation station, and the two are at the same height. Using the observation data from the two periods, the three-component magnetic field values ​​observed at the diurnal variation station at different times are converted into three-component magnetic fields in the same geographic coordinate system as the mobile station, thereby achieving vector correction of the diurnal magnetic variation in a time-synchronized manner. When specifically implemented, the field observation stage will be as follows:

[0041] A quiet location with a mild magnetic field and no interference near the work area is selected as the observation location for the diurnal variation station. The three-axis flux gate magnetometer probe (2) is stably installed on the probe holder (3). The three axes Mx, My, and Mz of the magnetometer probe (2) are approximately oriented geographically north, east, and vertically downward, respectively, and are not allowed to move. Before construction, the power is turned on to perform automatic continuous observation, and the time and magnetic measurement data are saved. The sampling frequency is set to step S1, which is higher than 1 Hz.

[0042] During the construction period, the magnetic measurement mobile station is transported to the diurnal variation station twice, in the morning and afternoon or in the afternoon and evening. The three-component magnetic probe (6) is stably installed on the T-shaped pipe shelf (9). The T-shaped pipe shelf (9) of the mobile station is installed near the magnetometer probe (2) of the diurnal variation station. The three axes Mx, My, and Mz of the three-component magnetic probe (6) of the mobile station are approximately oriented geographically north, east, and vertically downward, respectively, and are not allowed to move. The power is turned on to perform automatic continuous observations, and the time and magnetic measurement data are stored. The sampling frequency is the same as that of the diurnal variation station, and the sampling time can be 1 to 3 minutes. Step S2.

[0043] Step S3: In addition to conducting the above-mentioned synchronous observation, the mobile station is also used to conduct magnetic vector observation in the measurement network during other periods, and stores observation point, time, attitude and magnetic vector data, which are used to calculate the observation time and magnetic three-component data of each observation point at geographic coordinates; The magnetometer main body 1(1) of the day-changing station continuously observes and records at a predetermined sampling frequency during operation of the mobile station, and step S4 is included.

[0044] Of these, the magnetometer body 1 at the diurnal variation station cannot be shut down during operation at the mobile station, and while the magnetometer probe 2 at the diurnal variation station is not moving, the magnetic vector diurnal variation correction coefficients determined from the above two field synchronous observation data are both valid and are not affected by on / off. However, when the magnetometer probe 2 at the diurnal variation station moves, the above two synchronous observations must be performed again. For reasons of validity, it is recommended that observation work be performed daily according to the above magnetic diurnal variation correction. When specifically implemented, the indoor calculation stage is as follows:

[0045] Step S5: Analyze the observation data of the first period when the magnetic measurement mobile station is near the diurnal variation station, create a diurnal variation graph, select a smooth flat section of the curve, compare it with the diurnal variation curve of the magnetic measurement data of the diurnal variation station during the same period, and if the shapes of the two curves are consistent and stable and flat, select the magnetic three-component data of the diurnal variation station and the magnetic three-component data of the mobile station at a certain same time (at least synchronized to the second level) as the original inspection parameters of the first period for calculating the coordinate transformation coefficients;

[0046] Step S6: converting the magnetic three-component data of the mobile station at the selected specific time of the first period into magnetic three-component data in a geographic coordinate system based on the attitude sensor data (azimuth angle, pitch angle, and roll angle) at the same time;

[0047] The three magnetic component data (x mt1o , y mt1o , z mt1o ), the three-component magnetic data of the mobile station in the geographic coordinate system (x t1o , y t1o , z t1o ) and scale them all to a unit vector, and the processed three-component magnetic data (x mt1 , y mt1 , z mt1 ) and the three-component magnetic data (x t1 , y t1 , z t1 ) is step S7,

[0048]

number

[0049] Analyze the observation data of the second period when the magnetic measurement mobile station is near the diurnal variation station and the observation data of the diurnal variation station during that period, repeat the above steps S1, S2, and S3, and calculate the correction coefficient for the original inspection parameters (x mt2 , y mt2 , z mt2 ), (x t2 , y t2 , z t2 Step S8 to obtain The coordinate transformation coefficient matrix M is calculated using the following steps:

[0050]

number

[0051]

number

[0052]

number

[0053] Step S9: converting the three magnetic component values ​​measured at each time of the diurnal variation station into three magnetic component values ​​in a geographic coordinate system using matrix M; Correction for diurnal variation is performed using the coordinate transformation coefficient matrix M,

[0054]

number

[0055] where X mto , Y mto , Z mto are the three component values ​​of the original magnetic measurement data of the diurnal variation station at a certain time (t), and X to , Y to , Z to is the X mto , Y mto , Z mto are the three magnetic component values ​​converted into the geographic coordinate system. When correcting for diurnal variation, the magnetic vector data measured at the mobile station at the time (t) is converted into (X tn , Y tn , Z tn ) and then convert the magnetic three-component values ​​in the geographic coordinate system into X to , Y to , Z to That is,

[0056]

number

[0057] X t , Y t , Z t are the three magnetic component values ​​after diurnal variation correction of the three magnetic component data measured at the mobile station at that time (t), which correspond to the geographic coordinate system, and include step S10 in which the diurnal variation correction work of the magnetic vector is completed by processing all observation times in the above manner.

[0058] The technical effects of the above content are: the magnetic measurement mobile station adopts a device integrating a three-axis flux gate magnetometer body 2 (4) and an attitude indicator body (5), and can convert the three magnetic field components measured by the magnetometer body 2 (4) into three magnetic field components in a geographic coordinate system (corresponding to the three coordinate axes of geographic north, geographic east, and vertical downward) through conversion; the magnetic measurement diurnal variation station uses the static continuous observation mode of the three-axis flux gate magnetometer body 1 (1) to measure the three magnetic field component values ​​at different times in the same location; and by the method disclosed in the present invention, the three magnetic field component values ​​observed at different times by the diurnal variation station are converted into the three magnetic field components in the same geographic coordinate system as the magnetic measurement mobile station, and further, vector correction of the magnetic diurnal variation is performed by a time synchronization method. The present invention has stronger applicability than other correction methods, and the correction method adopted by the present invention can greatly improve the correction accuracy and reliability of the correction results. It does not require the use of orientation equipment such as theodolite, is not affected by orientation errors, makes field observation easier, is less affected by other peripheral interference, has a more stable correction effect, and has greater advantages in terms of coordinate system conversion, is completely unaffected by orientation errors of the magnetic probe case, and can perfectly convert the magnetic three-component data measured at the diurnal variation station into the same geographic coordinate system as the mobile station, thereby ensuring the accurate requirements for the orientation of the diurnal variation correction of magnetic vectors, and ensures the consistency and reliability of the diurnal variation correction results of multi-day and multi-period magnetic measurements. [Embodiment]

[0059] The objective of the present invention is to provide a method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration. In order to verify the accuracy of the above-mentioned method for correcting diurnal variation in magnetic vector measurement, this embodiment provides a technical solution with reference to Figures 3 to 7, including the following steps:

[0060] Step 1: A quiet location with a mild magnetic field and no human interference in the mountainous area west of Fuping, Baoding was selected as the observation point for the diurnal variation station. At the beginning of 2024, staff carried out field observations at this location. The equipment used for the diurnal variation observation was a British-made high-precision three-axis flux gate magnetometer body 1. The mobile station is equipped with a homemade system consisting of a British-made high-precision three-axis flux gate magnetometer (4), two three-component magnetic probes (6), and a high-precision attitude sensor (5) (with a built-in GPS system (11) and capable of measuring the azimuth, roll, and pitch angles of the three-component magnetic probe (6)). These are integrated into a single D-shaped vertical tube (12) (a "cross" frame) (see Figure 3). Two three-component magnetic probes (6) are fixed to the top and bottom of the D-shaped vertical tube (12), i.e., the top and bottom of the "cross" frame vertical tube, to measure the magnetic vector and its gradient. Considering only the top three-component magnetic probe (6), this is the same as the mobile station equipment described above. The bottom three-component magnetic probe (6) is primarily designed to measure gradients, and its correction calculation method is the same as that of the top probe.

[0061] The three-component magnetic data observed by the mobile station's three-component magnetic probe (6) can be converted into three-component magnetic data in a geographic coordinate system (X is geographic north, Y is geographic east, and Z is vertically downward) based on the attitude sensor data. The magnetometer probe (2) of the diurnal variation station is fixed to a magneticless probe holder (3) (which can be simplified to a 2m-long pile, with the magnetometer probe (2) fastened to the side of the top of the pile) and performs static continuous observations (the X magnetic axis of the magnetometer probe (2) points approximately to geographic north, the Y magnetic axis points approximately to geographic east, and the Z magnetic axis points approximately vertically downward), allowing the measurement of the three-component magnetic field values ​​at the same location at different times, and these three-component values ​​are independent of the geographic coordinate system.

[0062] To verify the accuracy of the diurnal variation correction method for magnetic vector measurements, the mobile station's three-component magnetic probe (6) and the diurnal variation station's magnetometer probe (2) were placed adjacent to each other during field measurements. The three-component magnetic probe (6) and the magnetometer probe (2) were spaced 1 m apart. Simultaneous static observations were conducted with the three-component magnetic probe (6) and the magnetometer probe (2) for at least one hour. Theoretically, the magnetic fields measured by the two probes should be nearly identical. To verify the coordinate transformation effect and the accuracy of the diurnal variation correction, the diurnal variation station's magnetometer probe (2) was intentionally tilted, resulting in a relatively large difference between its X, Y, and Z three-component orientation and the geographic orientation. If the diurnal variation correction method was correct, the corrected three-component data curves for the mobile station should all trend toward zero.

[0063] Step 2: Field observation starts at 7:00 a.m. on the day and ends at 10:00 a.m., and the sampling frequency of both the mobile station and the diurnal variation station is 1 Hz. Step 3: After completing the field work, perform the following process according to the indoor calculation method for correcting the diurnal variation of magnetic vectors described above.

[0064] Analysis showed that after synthesizing the total magnetic field from the three-component magnetic data continuously observed at the diurnal variation station and the mobile station, the changes in the total field data were essentially consistent, indicating the normality and reliability of the equipment. Because the amount of data is large, to demonstrate the accuracy of the diurnal variation correction method described in this invention, in this embodiment, data from the period 7:19:24 to 8:21:41 (time 5000 seconds, the abscissa in the attached graph is seconds, the ordinate is magnetic field value, unit nT) was selected to perform an exemplary diurnal variation correction. The three-component magnetic data curves observed at the diurnal variation station and the mobile station during this period are shown in Figures 4 and 6. Although the three-component data from both stations are not comparable, it can be seen that there is little difference between the two total magnetic field data.

[0065] The beginning and end of the period are used as matching points, the magnetic three-component data of the diurnal variation station and the magnetic three-component data of the mobile station at 7:19:24 are used as the original inspection parameters for the first period for calculating the coordinate transformation coefficients, and the magnetic three-component data of the diurnal variation station and the magnetic three-component data of the mobile station at 8:21:41 are used as the original inspection parameters for the second period for calculating the coordinate transformation coefficients, and the transformation matrix M is calculated according to the above steps.

[0066] Using the M matrix, the three-component magnetic values ​​measured at each time at the diurnal variation station are converted into three-component magnetic values ​​in the geographic coordinate system using the above-mentioned formulas. See Figure 5 for the conversion results (the period corresponds to the periods in Figures 4 and 6). It can be seen that the three-component curves of the diurnal variation station after conversion are almost identical to the three-component curves of the mobile station.

[0067] The diurnal variation correction was performed on the three-component magnetic data (corresponding to the geographic coordinate system) observed at the mobile station using the three-component magnetic data from the diurnal variation station converted to the geographic coordinate system (due to the time synchronization between the two, the diurnal variation correction was achieved by subtracting the same data from both stations at the same time). The correction results are shown in Figure 7 (the time periods correspond to those in Figures 4, 5, and 6). As can be seen from the difference in the total magnetic field observed by the mobile station and the diurnal variation station in Figure 7, there is a difference of several tens of nanoteslas between the two instruments at the mobile station and the diurnal variation station. This difference indicates a discrepancy in the consistency between the measurement results at the diurnal variation station and the mobile station. (There are many methods for consistency correction, but these are beyond the scope of this invention and will not be discussed here.) As can be seen from the bottom graph in Figure 7, the difference in the total magnetic field between the original observations at the mobile station and the diurnal variation station matches the difference curve between the two after coordinate transformation, indicating that the coordinate transformation is stable and reliable. Figure 7 shows that the three-component magnetic data after diurnal variation correction (i.e., the diurnal variation station data is subtracted from the mobile station data) tends toward almost zero (there is a residual value of about 10 nT, which is related to the above-mentioned difference in consistency), demonstrating the effectiveness and reliability of the magnetic vector diurnal variation correction method proposed in this invention.

[0068] Operating principle: The magnetic measurement mobile station adopts a device integrating a three-axis flux gate magnetometer body 2 (4) and an attitude sensor body (5), and can convert the three magnetic field components measured by the magnetometer body 2 (4) into three magnetic field components in a geographic coordinate system through conversion. The magnetic measurement diurnal variation station uses the static continuous observation mode of the three-axis flux gate magnetometer body 1 (1) to measure the three magnetic field component values ​​at different times in the same location. By using the method disclosed in this invention, the three magnetic field component values ​​observed at different times by the diurnal variation station can be converted into the three magnetic field components in the same geographic coordinate system as the magnetic measurement mobile station. The correction method adopted by the present invention can greatly improve the correction accuracy and the reliability of the correction results; it does not require the use of orientation equipment such as theodolite, is not affected by orientation errors, makes field observation easier, is less affected by other peripheral interference, has a more stable correction effect, and has greater advantages in terms of coordinate system conversion; it is completely unaffected by orientation errors of the magnetic probe case, and can perfectly convert the magnetic three-component data measured at the diurnal variation station into the same geographic coordinate system as the mobile station, thereby ensuring the accurate requirements for the orientation of the diurnal variation correction of magnetic vectors, and ensures the consistency and reliability of the diurnal variation correction results of multi-day and multi-period magnetic measurements.

[0069] The above is merely a special example of a specific embodiment of the present invention, and the scope of the present invention is not limited thereto. If a person skilled in the art makes equivalent substitutions or modifications based on the technical solutions and spirit of the present invention within the technical scope disclosed in the present invention, they will be included in the scope of the present invention. [Explanation of symbols]

[0070] 1. Magnetometer body 1, 2 magnetometer probes, 3 probe holders, 4 magnetometer body 2, 5 Attitude meter body, 6 three-component magnetic probes, 7. Attitude indicator forward positioning antenna; 8 Attitude indicator aft positioning antenna, 9 T type pipe shelf, 10 Pipe shelf fixing cable, 11 GPS system, 12 D-type vertical pipe

Claims

1. A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration, comprising two steps: a field observation step and an indoor calculation step, The field observation stage is divided into two parts: a diurnal change station magnetic vector measurement and a mobile station magnetic vector measurement. The diurnal change station magnetic vector measurement uses a diurnal change station measurement device, and the equipment used at the diurnal change station is mainly a general-purpose high-precision three-axis flux gate magnetometer body 1 (1). The mobile station magnetic vector measurement uses a field mobile measurement device, and the equipment used at the mobile station is mainly a general-purpose high-precision three-axis flux gate magnetometer body 2 (4) and a high-precision attitude meter body (5). The day-changing station measuring device is composed of a magnetometer body 1 (1), a magnetometer probe (2), and a probe holder (3), and the field mobile measuring device is composed of a magnetometer body 2 (4), an attitude meter body (5), a three-component magnetic probe (6), an attitude meter forward positioning antenna (7), an attitude meter rearward positioning antenna (8), a T-shaped pipe shelf (9), and a pipe shelf fixing cable (10). A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration.

2. The magnetic three-component data observed in the survey network by the mobile station is converted into magnetic three-component data in a geographic coordinate system based on the data of the attitude sensor body (5).

2. A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration according to claim 1.

3. The diurnal variation station uses the static continuous observation mode of the three-axis flux gate magnetometer main body 1 (1) to measure the three magnetic field components at different times at the same location. During the field observation stage, a mobile station is installed at the diurnal variation station twice a day, in the morning and in the afternoon, and continuous observations are performed synchronously with the diurnal variation station.

2. A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration according to claim 1.

4. The three-component magnetic probe (6) of the mobile station is approximately 50 cm away from the magnetometer probe (2) of the diurnal variation station, and the two are at the same height. Based on the observation data from the two periods, the three magnetic field components observed at the diurnal variation station at different times are converted into three magnetic field components in the same geographic coordinate system as the mobile station, thereby achieving vector correction of the diurnal magnetic variation in a time-synchronized manner.

2. A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration according to claim 1.

5. The field observation step includes: A quiet place with a mild magnetic field and no interference near the work area is selected as the observation location of the diurnal variation station. The three-axis flux gate magnetometer probe (2) is stably installed on the probe holder (3). The three axes Mx, My, and Mz of the magnetometer probe (2) are approximately directed toward the geographic north, east, and vertically downward, respectively, and are not allowed to move. Before construction, the power is turned on to perform automatic continuous observation, and the time and magnetic measurement data are saved. The sampling frequency is higher than 1 Hz. Step S1. During the construction period, in the morning and afternoon or in the afternoon and evening, the magnetic measurement mobile station is transported to the diurnal variation station twice, the three-component magnetic probe (6) is stably installed on the T-shaped pipe shelf (9), the T-shaped pipe shelf (9) of the mobile station is installed near the magnetometer probe (2) of the diurnal variation station, the three axes Mx, My, Mz of the three-component magnetic probe (6) of the mobile station are approximately oriented geographically north, east, and vertically downward, respectively, and are not allowed to move, the power is turned on to perform automatic continuous observation, the time and magnetic measurement data are stored, the sampling frequency is the same as that of the diurnal variation station, and the sampling time can be 1 to 3 minutes (step S2); Step S3: In addition to conducting the above-mentioned synchronous observation, the mobile station is also used to conduct magnetic vector observation in the measurement network during other periods, and stores observation point, time, attitude and magnetic vector data, which are used to calculate the observation time and magnetic three-component data of each observation point at geographic coordinates; Step S4: The magnetometer main body 1 (1) of the day-changing station continuously observes and records at a predetermined sampling frequency during operation of the mobile station; Contains 2. A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration according to claim 1.

6. The indoor calculation step includes: Step S5: Analyzing the observation data of a first period when the magnetic measurement mobile station is near the diurnal variation station, creating a diurnal variation curve graph, selecting a smooth, flat section of the curve, comparing it with the diurnal variation curve of the magnetic measurement data of the diurnal variation station during the same period, and finding that the shapes of the two curves are consistent and stable and flat, and selecting the magnetic three-component data of the diurnal variation station and the magnetic three-component data of the mobile station at a certain time as the original inspection parameters of the first period for calculating the coordinate transformation coefficients; Step S6: converting the magnetic three-component data of the mobile station at the selected specific time of the first period into magnetic three-component data in a geographic coordinate system based on the attitude sensor data at the same time; Magnetic three-component data x of the diurnal variation station at the specific time above ｍｔ１ｏ , y ｍｔ１ｏ , z ｍｔ１ｏ , the magnetic three-component data x of the mobile station in the geographic coordinate system ｔ１ｏ , y ｔ１ｏ , z ｔ１ｏ and are normalized and scaled to a unit vector, and the processed three-component magnetic data of the diurnal variation station x ｍｔ１ , y ｍｔ１ , z ｍｔ１ and the magnetic three-component data x of the mobile station in the geographic coordinate system. ｔ１ , y ｔ１ , z ｔ１ Step S7, where: [Equation 1] The magnetic measurement mobile station analyzes the observation data of the second period when the magnetic measurement mobile station is near the diurnal variation station and the observation data of the diurnal variation station during the second period, and repeats the above steps S1, S2, and S3 to calculate the correction coefficient. ｍｔ２ , y ｍｔ２ , z ｍｔ２ , x ｔ２ , y ｔ２ , z ｔ２ Step S8 to obtain The coordinate transformation coefficient matrix M is calculated by the following steps: [Equation 2] [Equation 3] [Equation 4] Step S9: converting the magnetic three-component values ​​measured at each time of the diurnal variation station into magnetic three-component values ​​in a geographic coordinate system using matrix M; Correction for diurnal variation is performed using the coordinate transformation coefficient matrix M, [Equation 5] Here, X ｍｔｏ , Y ｍｔｏ , Z ｍｔｏ are the three component values ​​of the original magnetic measurement data of the diurnal variation station at a certain time (t), and X ｔｏ , Y ｔｏ , Z ｔｏ is the X ｍｔｏ , Y ｍｔｏ , Z ｍｔｏ are the three magnetic component values ​​converted into the geographic coordinate system, and when correcting for diurnal variation, the magnetic vector data measured at the mobile station at the time (t) is converted into X ｔｎ , Y ｔｎ , Z ｔｎ Then, the magnetic three component values ​​in the geographic coordinate system are converted into X ｔｏ , Y ｔｏ , Z ｔｏ That is, [Equation 6] X ｔ , Y ｔ , Z ｔ are the three magnetic component values ​​after diurnal variation correction of the three magnetic component data measured at the mobile station at that time (t), which correspond to the geographic coordinate system, and are processed in the above manner for all observation times, thereby completing the diurnal variation correction work of the magnetic vector in step S10; Contains 2. A method for correcting diurnal magnetic variation in geomagnetic vector measurement for exploration according to claim 1.

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