Method for laying measuring points in magnetotelluric exploration

Abstract

The invention relates to the field of geophysical exploration, and discloses a method for laying measuring points in magnetotelluric exploration, which comprises the following steps of: pre-arranging measuring lines and measuring points according to a target task in combination with geological and satellite image data; rTK measurement equipment is used to connect a high-precision positioning service to obtain a fixed solution; real-time differential high-precision positioning is carried out on the designed measuring points, and the positions of the measuring points are adjusted; taking the adjusted measuring point as a center, respectively determining the positions of two groups of orthogonal electrodes in two directions by using real-time differential high-precision positioning, and recording the distance between the two groups of electrodes; two points are positioned in a real-time differential high-precision manner to determine the orientation of the magnetic bar, and the magnetic bar is embedded; the magnetotelluric exploration equipment is used for collecting electromagnetic signals of corresponding frequency bands to be combined with the electrode distance, and the tensor impedance of each measuring point is calculated to obtain apparent resistivity and phase data. According to the invention, the distance measuring function of a measuring tape or a measuring rope is comprehensively replaced, the precision of horizontal distance measurement is guaranteed, and the data quality is improved for the calculation of apparent resistivity.

Description

Technical Field

[0001] The invention relates to the field of geophysical exploration, and in particular to a method for arranging measuring points for magnetotelluric exploration. Background Art

[0002] Magnetotelluric exploration is one of the main methods of geophysical exploration. It is an electromagnetic exploration method that detects the electrical differences of rocks in the crust and upper mantle by observing the changes of alternating electromagnetic fields of different frequencies on the ground. A set of mutually orthogonal horizontal electrical components is laid out on the ground, and a set of mutually orthogonal horizontal magnetic components are observed at each measuring point or arrangement (vertical magnetic components need to be laid out for full tensor observation). The lower the frequency of magnetotelluric exploration, the deeper the electrical information can be obtained. Through data processing and interpretation, it is widely used in solid geophysical research, energy resource detection, solid mineral exploration, hydrological environment and disaster geological investigation, etc., providing strong support for modernization development.

[0003] When collecting field data for magnetotelluric exploration, there are many factors that affect the data quality, such as human electromagnetic interference, low-resistance stratum shielding interference, high ground resistance, and the regularity of field source signals. Most of these factors are widely concerned and corresponding remedial measures have been taken.

[0004] However, the accuracy and efficiency of measuring point layout are often neglected, especially in forest areas with developed vegetation, mountainous areas with large terrain undulations, and areas of local geomagnetic field interference. The previous method of laying out electrodes and magnetic bars has greatly reduced work efficiency and data quality due to poor visibility conditions and low accuracy. Summary of the invention

[0005] The purpose of the present invention is to provide a method, device and storage medium for arranging measuring points for magnetotelluric exploration, so as to solve the technical problems such as poor horizontal positioning and orientation accuracy and low measuring point arrangement efficiency when arranging electrodes and magnetic bars for magnetotelluric exploration.

[0006] The present invention provides a method for setting measurement points for magnetotelluric exploration, comprising the following steps: S1: Pre-arrange survey lines and points based on the target mission combined with geological and satellite image data; S2: Use RTK measurement equipment to connect to high-precision positioning services to obtain fixed solutions; S3: Perform real-time differential high-precision positioning on the designed measuring points and adjust the positions of the measuring points; S4: With the adjusted measuring point as the center, use real-time differential high-precision positioning to determine the positions of two groups of orthogonal electrodes in two directions respectively, and record the distances between the two groups of electrodes; S5: Use real-time differential high-precision positioning of two points to determine the orientation of the magnetic bar and bury the magnetic bar; S6: Use magnetotelluric exploration equipment to collect electromagnetic signals of the corresponding frequency band and combine them with the electrode distance, calculate the tensor impedance of each measuring point to obtain apparent resistivity and phase data.

[0007] The beneficial effects provided by the present invention are: 1. In previous work, a forest compass was used to orient a horizontally placed magnetic bar using a mechanical compass. This method has three problems. The first is that when the underground residual magnetization intensity is large, especially when the local magnetic anomaly changes strongly in the mining area, the compass's direction deviates far beyond the technical requirement of the electromagnetic method that the azimuth deviation is less than 1 degree. The second is that the compass is seriously affected by magnetic interference, especially when the operator carries magnetic objects and there are magnetic materials that are difficult to detect around. The third is that the observation of the forest compass requires a line of sight. If data is collected in forest areas and mountainous areas with developed vegetation, it is necessary to cut down and open roads in the directions of the four electrodes and the two horizontal magnetic components. This not only consumes a lot of manpower and material resources, but also greatly reduces work efficiency.

[0008] The present invention provides a method for setting measuring points for magnetotelluric exploration based on RTK high-precision positioning, which can completely replace the function of the forest compass. It only needs people to pass through without cutting down multiple sight lines. The high accuracy of RTK high-precision positioning can fully meet the technical requirement of magnetotelluric exploration for an azimuth deviation of less than 1 degree. Therefore, the method provided by the present invention can both ensure data quality and improve work efficiency.

[0009] 2. In previous work, tape measures or measuring ropes were used to measure the pole distances of two groups of electrical components. This method has two problems. The first is that in areas with large terrain undulations, the length measured by the measuring rope is the length of the curve close to the surface undulations, which deviates from the horizontal distance of the pole distances in magnetotelluric exploration. The second is that in forest areas and mountainous areas with developed vegetation, due to the interference of shrubs and weeds, it is difficult to straighten the general measuring rope, which also causes the measured length to fail to meet the technical requirements. The present invention provides a method for setting measuring points for magnetotelluric exploration based on RTK high-precision positioning, which can completely replace the distance measurement function of tape measures or measuring ropes, ensure the accuracy of horizontal distance measurement, and improve the data quality for electric field emphasis calculation.

[0010] 3. In previous work, RTK was used to locate two groups of four electric components, while the forest compass was still used for orientation determination by magnetic rods. The positioning of RTK belongs to geographic north, while the orientation of the forest compass belongs to magnetic north. These two orientations are not orientations in the same coordinate system, and it is difficult to ensure the technical requirement that the azimuth deviation between the electric component and the magnetic component is less than 1 degree. At the same time, the forest compass has the above problems. The present invention provides a method for setting measuring points for magnetotelluric exploration based on RTK high-precision positioning. When determining the azimuths of the electric component and the magnetic component, both belong to geographic north and belong to the same set of coordinates. As long as the positioning accuracy is ensured, the technical requirement that the azimuth deviation between the two is less than 1 degree can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic flow chart of the method of the present invention; Figure 2 It is a schematic diagram of the positions of two groups of orthogonal electrodes along the north-south and east-west directions during single-point measurement of magnetotelluric exploration in an embodiment of the present application; Figure 3 It is a schematic diagram of the positions of two groups of orthogonal electrodes along two directions parallel and perpendicular to the survey line during single-point measurement of magnetotelluric exploration in an embodiment of the present application; Figure 4 It is a schematic diagram of the positions of two groups of orthogonal electrodes along the north-south and east-west directions during the common magnetic track multi-point measurement of magnetotelluric exploration in an embodiment of the present application; Figure 5 It is a schematic diagram of the positions of two groups of orthogonal electrodes along two directions parallel and perpendicular to the survey line during the common magnetic track multi-point measurement of magnetotelluric exploration in an embodiment of the present application; Figure 6 This is a schematic diagram of the layout of horizontal tracks in magnetotelluric exploration in an embodiment of the present application; Figure 7 It is a schematic diagram of the vertical track layout in magnetotelluric exploration in an embodiment of the present application; Figure 8 It is a schematic diagram of the RTK positioning measurement path of the magnetotelluric exploration measurement points in the embodiment of the present application. DETAILED DESCRIPTION

[0012] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0013] Before formally describing the present invention, the scheme of the present invention is first generally described for easy understanding.

[0014] First, the application scenario of the present application is introduced. The present application can be applied to the field of magnetotelluric survey point deployment technology.

[0015] Please refer to Figure 1 , Figure 1 It is a schematic flow diagram of the method of the present invention; The present invention provides a method for arranging measuring points for magnetotelluric exploration, comprising the following steps: S1: Pre-arrange survey lines and points based on the target mission combined with geological and satellite image data; It should be noted that after obtaining the target mission of magnetotelluric exploration, the geological data should be combined to make the direction of the survey line perpendicular to the structural trend to obtain the maximum structural anomaly resolution. With the assistance of satellite image data, the survey line should be pre-deployed to avoid residential areas, high-voltage lines and other serious interference areas as much as possible. At the same time, the survey line needs to run through the study area and extend the effective detection depth at both ends.

[0016] Determine the distance between measuring points according to the relevant electromagnetic exploration specifications, and ensure that at least 3 measuring points are located within the distribution range of the target body. For key areas, the measuring points can be appropriately encrypted to ensure the data quality of the survey line. This invention is only for schematic illustration and is not intended to be limiting.

[0017] S2: Use RTK measurement equipment to connect to high-precision positioning services to obtain fixed solutions; It should be noted that step S2 specifically includes: importing the pre-arranged measurement point coordinates into the RTK measurement device, and connecting the RTK device to a high-precision positioning service in an open area to obtain the actual coordinates of the measurement points.

[0018] As an embodiment, the specific operation of step S2 is as follows: When positioning the measurement points on the field, first import the pre-deployed measurement point coordinates into the RTK measurement device. In an open area in the wild, connect the RTK device to the CORS service and obtain a fixed solution.

[0019] In the present invention, RTK high-precision positioning refers to real-time kinematic positioning technology (abbreviated as RTK); CORS service (continuous operational reference system, referred to as CORS) is a platform service that provides real-time differential signals for RTK measurement equipment through wireless communication.

[0020] RTK survey equipment in CORS service can obtain fixed solutions around the clock, with a horizontal coordinate positioning accuracy of ±2cm and an elevation positioning accuracy of ±5cm.

[0021] Preferably, the Qianxunzhicun CORS service is generally used. In addition, the China Mobile CORS service and the CORS services of various provinces can also be used.

[0022] It should be noted that in areas with poor network signals, Qianxun Service also provides Qianxun satellite-ground communication technology, which deeply integrates ground-based, network-based and satellite-based systems to achieve high-precision fixed solution positioning with real-time differential signals even without a network.

[0023] S3: Perform real-time differential high-precision positioning on the designed measuring points and adjust the positions of the measuring points; It should be noted that step S3 specifically includes: navigating to the actual coordinates of the measuring point, and adjusting the measuring point again within the point distance radius preset by the actual coordinates of the measuring point to obtain the adjusted measuring point, and again using the RTK measuring device to obtain the actual coordinates of the adjusted measuring point.

[0024] As an embodiment, the specific operation of step S3 is as follows: Use RTK surveying equipment to navigate to the measuring point. According to the actual situation in the field, avoid interference sources as much as possible and choose a place that is convenient for setting up the measuring point construction.

[0025] The actual measuring point position can be appropriately adjusted within a circle with a radius of 10% of the point spacing. For areas with difficult construction, the adjustment can be relaxed to a circle with a radius of 20% of the point spacing. The purpose of this is to efficiently collect high-quality data in the field.

[0026] After determining the position of the measuring point, use RTK measuring equipment to obtain the fixed solution three-dimensional coordinates of the actual measuring point.

[0027] S4: With the adjusted measuring point as the center, use real-time differential high-precision positioning to determine the positions of two groups of orthogonal electrodes in two directions respectively, and record the distances between the two groups of electrodes; It should be noted that, during the magnetotelluric survey measurement in step S4, a single-point measurement or a common-track multi-point measurement device may be used.

[0028] As an example, no matter what kind of device is used, the azimuths of its two groups of electric track components must be arranged parallel to the two horizontal magnetic track components, and the azimuth deviation should be less than 1 degree, and the electrode spacing error should be less than 1%. Where construction conditions permit, a "ten" type pole layout should be used as much as possible; in areas with difficult terrain, a "T" type or "L" type pole layout can be used. This is only for schematic illustration and is not intended to be limiting.

[0029] Please refer to Figure 2 , Figure 2 It is a schematic diagram of the positions of two groups of orthogonal electrodes along the north-south and east-west directions during single-point measurement of magnetotelluric exploration in an embodiment of the present application.

[0030] Figure 2 In the process, taking the horizontal coordinates of the measuring point as the center, RTK high-precision positioning is used to determine the positions of two groups of orthogonal electrodes in the north-south and east-west directions respectively, and the parameters of the two groups of electrode distances are recorded.

[0031] The coordinates of the two end points of the measuring line are: A (Ax, Ay), B (Bx, By); the coordinates of the actual measuring point on the measuring line are Ci_0 (Ci_0x, Ci_0y), where i is the i-th measuring point. Therefore, the coordinates of the four electrodes are Ci_1 (Ci_0x+Dni, Ci_0y), Ci_2 (Ci_0x, Ci_0y+Dei), Ci_3 (Ci_0x-DSi, Ci_0y), Ci_4 (Ci_0x, Ci_0y-Dwi). Therefore, the distance between the two sets of electrical components of each measuring point is (Dx=Dni+Dsi, Dy=Dwi+Dei).

[0032] Please refer to Figure 3 , Figure 3 It is a schematic diagram of the positions of two groups of orthogonal electrodes along two directions parallel and perpendicular to the survey line during single-point measurement of magnetotelluric exploration in an embodiment of the present application; like Figure 3 As shown in the figure, taking the horizontal coordinate of the measuring point as the center, the RTK high-precision positioning is used to determine the positions of two groups of orthogonal electrodes along the measuring line and in the direction perpendicular to the measuring line, and the two groups of electrode distance parameters are recorded.

[0033] The coordinates of the two end points of the measuring line are: A (Ax, Ay), B (Bx, By); the coordinates of the actual measuring point on the measuring line are Ci_0 (Ci_0x, Ci_0y), where i is the i-th measuring point. Therefore, the coordinates of the four electrodes are Ci_1 (Ci_1x, Ci_1y), Ci_2 (Ci_2x, Ci_2y), Ci_3 (Ci_3x, Ci_3y), Ci_4 (Ci_4x, Ci_4y), and the distance between the two groups of electrical components of each measuring point is (Dx=Dni+Dsi, Dy=Dwi+Dei). Among them: Ci_1x= , Ci_1y= , Ci_2x= , Ci_2y= , Ci_3x= , Ci_3y= , Ci_4x= , Ci_4y= .

[0034] Please refer to Figure 4 , Figure 4 It is a schematic diagram of the positions of two groups of orthogonal electrodes along the north-south and east-west directions during the common magnetic track multi-point measurement of magnetotelluric exploration in an embodiment of the present application; like Figure 4 As shown in the figure, taking the horizontal coordinates of each measuring station as the center, RTK high-precision positioning is used to determine the positions of two groups of orthogonal electrodes in the north-south and east-west directions respectively, and the parameters of the two groups of electrode distances are recorded.

[0035] Please refer to Figure 5 , Figure 5 It is a schematic diagram of the positions of two groups of orthogonal electrodes along two directions parallel and perpendicular to the survey line during the common magnetic track multi-point measurement of magnetotelluric exploration in an embodiment of the present application; like Figure 5 As shown in the figure, with the horizontal coordinates of each measuring station as the center, RTK high-precision positioning is used to determine the positions of two groups of orthogonal electrodes along the survey line and in the direction perpendicular to the survey line, and the two groups of electrode distance parameters are recorded.

[0036] S5: Use real-time differential high-precision positioning of two points to determine the orientation of the magnetic bar and bury the magnetic bar; It should be noted that the two horizontal magnetic bars (Hx, Hy) must be consistent with the direction of the two sets of electric components (Ex, Ey), and the azimuth deviation should be less than 1 degree. Determine two places to place magnetic bars at a certain distance away from the measuring point, use RTK to locate one point with high precision, and then locate another point about 3m along the azimuth of the electric component. When the positioning deviation is less than ±5cm, it can ensure that the azimuth deviation is less than 1 degree.

[0037] The orientation of the magnetic bar Hx must be parallel to the electric component Ex, and the azimuth deviation in the two directions is less than 1 degree. The orientation of the magnetic bar Hy must be parallel to the electric component Ey, and the azimuth deviation in the two directions is less than 1 degree.

[0038] As an example, please refer to Figure 6 , Figure 6 This is a schematic diagram of the layout of horizontal tracks in magnetotelluric exploration in an embodiment of the present application; like Figure 6 As shown, a laser level positioning device is used to connect the two points that determine the direction of the magnetic rod into a laser line of sight, a groove with a depth of not less than 30 cm is cut at the laser line of sight, the corresponding magnetic rod is placed in the groove and the position is slightly adjusted to ensure that it is parallel to the positioning device, and finally compacted and buried.

[0039] Please refer to Figure 7 , Figure 7 It is a schematic diagram of the vertical track layout in magnetotelluric exploration in an embodiment of the present application; like Figure 7As shown, for full tensor observation, it is necessary to deploy a vertical magnetic rod Hz with a clockwise angle of 225 degrees in the Hx direction, and use RTK high-precision positioning at a certain distance from the center of the measuring point. The vertical magnetic rod should be buried underground for at least 2 / 3 of its length, and a laser level should be used to ensure that the verticality error is no greater than 1 degree.

[0040] Please refer to Figure 8 , Figure 8 This is a schematic diagram of the RTK positioning measurement path for the magnetotelluric survey deployment points in the embodiment of the present application; like Figure 8 As shown in the figure, when measuring points are arranged in the field for magnetotelluric exploration, RTK high-precision positioning is used to achieve measuring point positioning, electrode positioning, and magnetic rod positioning and orientation. The survey is carried out in the order of the numbers marked in the figure from small to large, which can improve the speed and accuracy of measuring point arrangement. S6: Use magnetotelluric exploration equipment to collect electromagnetic signals of corresponding frequency bands and combine them with electrode distances to calculate the tensor impedance of each measuring point to obtain apparent resistivity and phase data; In step S6, after the two sets of electric and magnetic components of the measuring points are arranged, the magnetotelluric exploration equipment is turned on to collect data. After the data collection is completed, the measured electric component voltage difference data is , and the pole distance of the electric component and Convert to electric field strength and , combined with the measured magnetic field components Hx, Hy and Hz, the tensor impedance or full tensor impedance of each measuring point is calculated to obtain the apparent resistivity and phase data of the homogeneous medium. The specific calculation is as follows: , , , , , , in, and are the apparent resistivity in TE polarization mode and TM polarization mode, respectively; and These are the impedance phase data of TE polarization mode and TM polarization mode respectively; is the frequency, is the magnetic permeability of the medium; The ground electromagnetic apparent resistivity and phase data of the entire survey line or survey surface are inverted to obtain the two-dimensional underground resistivity distribution characteristics of the entire survey line or the three-dimensional underground resistivity distribution characteristics of the survey surface, as shown in the following formula: , in, is the overall objective function of magnetotelluric inversion, Here, the resistivity, is the observation data error matrix, The observed data here refers to the apparent resistivity and impedance phase data, According to the model, the predicted data is obtained through finite element forward simulation. is the regularization coefficient, is the model minimum and smoothness matrix, For reference model.

[0041] As an embodiment, two sets of electric components and magnetic components of measuring points are arranged through the above steps, and the magnetotelluric exploration equipment can be turned on to collect data. First, the grounding conditions of the two sets of electrodes are checked. When the grounding resistance is higher than 2000Ω·m, measures need to be taken to reduce the grounding resistance.

[0042] Set the equipment acquisition parameters according to the design requirements, collect electromagnetic signals of the corresponding frequency band, and save the data in the memory. After the data acquisition is completed, the measured electric component data Ex, Ey and the pole distances Dx and Dy of the electric component are combined with the measured magnetic field components Hx, Hy and Hz to calculate the tensor impedance or full tensor impedance of each measuring point to obtain the homogenized apparent resistivity and phase data.

[0043] By performing data inversion on the ground electromagnetic apparent resistivity and phase data of the entire survey line or surface, the two-dimensional underground resistivity distribution characteristics of the entire survey line or the three-dimensional underground resistivity distribution characteristics of the survey surface can be obtained.

[0044] The inversion results are combined with geological data, and drilling data or other geophysical data are collected as much as possible for comprehensive interpretation and research to provide geological interpretation results of underground electrical characteristics for the research objectives.

[0045] The beneficial effects of the present invention are: 1. In previous work, a forest compass was used to locate a horizontally placed magnetic rod using a mechanical compass. This method has three problems. The first is that when the underground residual magnetization intensity is large, especially when the local magnetic anomaly changes strongly in the mining area, the compass's direction deviates far beyond the technical requirement of the electromagnetic method that the azimuth deviation is less than 1 degree. The second is that the compass is seriously affected by magnetic interference, especially when the operator carries magnetic objects and there are magnetic materials around that are difficult to detect. The third is that the observation of the forest compass requires a line of sight. If data is collected in forest areas and mountainous areas with developed vegetation, it is necessary to cut down and open roads in the directions of the four electrodes and the two horizontal magnetic components. This not only consumes a lot of manpower and material resources, but also greatly reduces work efficiency.

[0046] The present invention provides a method for setting measuring points for magnetotelluric exploration based on RTK high-precision positioning, which can completely replace the function of the forest compass. It only needs people to pass through without cutting down multiple sight lines. The high accuracy of RTK high-precision positioning can fully meet the technical requirement of magnetotelluric exploration for an azimuth deviation of less than 1 degree. Therefore, the method provided by the present invention can both ensure data quality and improve work efficiency.

[0047] 2. In previous work, tape measures or measuring ropes were used to measure the pole distances of two groups of electrical components. This method has two problems. The first is that in areas with large terrain undulations, the length measured by the measuring rope is the length of the curve close to the surface undulations, which deviates from the horizontal distance of the pole distances in magnetotelluric exploration. The second is that in forest areas and mountainous areas with developed vegetation, due to the interference of shrubs and weeds, it is difficult to straighten the general measuring rope, which also causes the measured length to fail to meet the technical requirements. The present invention provides a method for setting measuring points for magnetotelluric exploration based on RTK high-precision positioning, which can completely replace the distance measurement function of tape measures or measuring ropes, ensure the accuracy of horizontal distance measurement, and improve the data quality for the calculation of electric field strength.

[0048] 3. In previous work, RTK was used to locate two groups of four electric components, while the forest compass was still used for orientation determination by magnetic rods. The positioning of RTK belongs to geographic north, while the orientation of the forest compass belongs to magnetic north. These two orientations are not orientations in the same coordinate system, and it is difficult to ensure the technical requirement that the azimuth deviation between the electric component and the magnetic component is less than 1 degree. At the same time, the forest compass has the above problems. The present invention provides a method for setting measuring points for magnetotelluric exploration based on RTK high-precision positioning. When determining the azimuths of the electric component and the magnetic component, both belong to geographic north and belong to the same set of coordinates. As long as the positioning accuracy is ensured, the technical requirement that the azimuth deviation between the two is less than 1 degree can be ensured.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for setting measurement points for magnetotelluric exploration, characterized in that: The method comprises the following steps: S1: Pre-arrange survey lines and points based on the target mission combined with geological and satellite image data; S2: Use RTK measurement equipment to connect to high-precision positioning services to obtain fixed solutions; S3: Perform real-time differential high-precision positioning on the designed measuring points and adjust the positions of the measuring points; S4: With the adjusted measuring point as the center, use real-time differential high-precision positioning to determine the positions of two groups of orthogonal electrodes in two directions respectively, and record the distances between the two groups of electrodes; S5: Use real-time differential high-precision positioning of two points to determine the orientation of the magnetic bar and bury the magnetic bar; S6: Use magnetotelluric exploration equipment to collect electromagnetic signals of the corresponding frequency band and combine them with the electrode distance, calculate the tensor impedance of each measuring point to obtain apparent resistivity and phase data.

2. A method for setting measuring points for magnetotelluric exploration according to claim 1, characterized in that: Step S2 specifically includes: importing the coordinates of the pre-arranged measuring points into the RTK measuring device, and connecting the RTK device to a high-precision positioning service in an open area to obtain the actual coordinates of the measuring points.

3. A method for setting measuring points for magnetotelluric exploration as claimed in claim 2, characterized in that: Step S3 specifically includes: navigating to the actual coordinates of the measuring point, and adjusting the measuring point again within the point distance radius preset by the actual coordinates of the measuring point to obtain the adjusted measuring point, and again using the RTK measuring device to obtain the actual coordinates of the adjusted measuring point.

4. The method for setting measurement points for magnetotelluric exploration according to claim 1, characterized in that: When determining two groups of orthogonal electrodes in step S4, there are multiple ways, including: single-point measurement and common-track multi-point measurement.

5. A method for setting measuring points for magnetotelluric exploration as claimed in claim 4, characterized in that: When single-point measurement is used, the horizontal coordinates of the measuring point are used as the center, and RTK high-precision positioning is used to determine the positions of two sets of orthogonal electrodes in the north-south and east-west directions respectively, and the parameters of the two sets of electrode distances are recorded.

6. A method for setting measurement points for magnetotelluric exploration as claimed in claim 4, characterized in that: During the single-point measurement, the positions of two groups of orthogonal electrodes along the survey line and in the direction perpendicular to the survey line are respectively determined using RTK high-precision positioning with the horizontal coordinates of the survey point as the center, and the two groups of electrode distance parameters are recorded.

7. A method for setting measurement points for magnetotelluric exploration as claimed in claim 4, characterized in that: When using common magnetic track multi-point measurement, the horizontal coordinates of each measuring station are taken as the center, and RTK high-precision positioning is used to determine the positions of two sets of orthogonal electrodes in the north-south and east-west directions respectively, and the two sets of electrode distance parameters of each measuring point are recorded respectively.

8. The method for setting measurement points for magnetotelluric exploration according to claim 4, characterized in that: When using common magnetic track multi-point measurement, the horizontal coordinates of each measuring station are taken as the center, and RTK high-precision positioning is used to determine the positions of two sets of orthogonal electrodes along the survey line and perpendicular to the survey line, and the two sets of electrode distance parameters of each measuring point are recorded respectively.

9. The method for setting measurement points for magnetotelluric exploration according to claim 4, characterized in that: In step S5, the directions of the two horizontal magnetic bars Hx, Hy are consistent with the directions of the two groups of electric components Ex, Ey, and the azimuth deviation is less than 1 degree.

10. The method for setting measurement points for magnetotelluric exploration according to claim 1, characterized in that: In step S6, after the two sets of electric and magnetic components of the measuring points are arranged, the magnetotelluric exploration equipment is turned on to collect data. After the data collection is completed, the measured electric component voltage difference data is , and the pole distance of the electric component and Convert to electric field strength and , combined with the measured magnetic field components Hx, Hy and Hz, the tensor impedance or full tensor impedance of each measuring point is calculated to obtain the apparent resistivity and phase data of the homogeneous medium. The specific calculation is as follows: ， ， ， ， ， ， in, and are the apparent resistivity in TE polarization mode and TM polarization mode, respectively; and These are the impedance phase data of TE polarization mode and TM polarization mode respectively; is the frequency, is the magnetic permeability of the medium; The ground electromagnetic apparent resistivity and phase data of the entire survey line or survey surface are inverted to obtain the two-dimensional underground resistivity distribution characteristics of the entire survey line or the three-dimensional underground resistivity distribution characteristics of the survey surface, as shown in the following formula: ， in, is the overall objective function of magnetotelluric inversion, Here, the resistivity, is the observation data error matrix, The observed data here refers to the apparent resistivity and impedance phase data, According to the model, the predicted data is obtained through finite element forward simulation. is the regularization coefficient, is the model minimum and smoothness matrix, For reference model.

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