A method for moving footprint stacking of full waveform continuous sampling data of ground-air transient electromagnetic

Abstract

The application discloses a ground-air transient electromagnetic full waveform continuous sampling data mobile footprint superposition method, and specifically comprises the following steps: step 1, signal emission and reception are carried out by using a ground-air transient electromagnetic exploration system; step 2, the continuous sampling data are sorted and matched with coordinates; step 3, periodicity identification is carried out on the full waveform data after sorting and coordinate matching; step 4, the data after periodic alignment are subjected to positive and negative square wave superposition, and the superposition is carried out by using a relative distance weighting method in space, so that finally, data with higher quality and precision after optimization are obtained; step 41, the data after positive and negative square wave superposition are obtained by carrying out positive and negative square wave superposition on the data after periodic alignment; and step 42, dense sampling data after superposition are obtained by carrying out relative distance weighting superposition on the data after positive and negative square wave superposition of each period. It is verified that the method effectively improves the precision of the data collected by the ground-air transient electromagnetic system.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration and relates to a method for superimposing moving footprints of continuous sampling data of transient electromagnetic full waveforms between the ground and the air. Background Technology

[0002] Ground-to-air transient electromagnetic (GTE) methods are widely used in mineral exploration and engineering applications due to their advantages over ground-based GTE methods, such as flexible transceiver equipment, good terrain adaptability, and high efficiency. Compared to airborne GTE methods, they offer greater exploration depth, higher signal-to-noise ratio, and lower cost. However, in practical applications, it has been found that during continuous sampling of GTE data, issues arise such as discontinuous data acquisition over time, misalignment of data acquisition periods by the signal acquisition unit, and inconsistent UAV flight speeds, leading to decreased sampling accuracy at sampling points. Furthermore, the inconsistency in UAV flight speed during sampling prevents the GTE system from achieving high-precision sampling at preset points, thus affecting the accuracy of the acquired data.

[0003] In summary, there is an urgent need to research a technology that can improve the accuracy of data acquired by the ground-to-air transient electromagnetic method. Summary of the Invention

[0004] The purpose of this invention is to provide a method for superimposing moving footprints of continuous sampling data of ground-to-air transient electromagnetic fields, so as to solve the technical problem of reduced exploration accuracy caused by continuous sampling of ground-to-air transient electromagnetic fields in the prior art.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A method for superimposing moving footprints from continuous sampling data of ground-to-air transient electromagnetic full waveforms includes the following steps: Step 1: Use a ground-to-air transient electromagnetic exploration system for signal transmission and reception; Step 2: Sort and match the coordinates of the continuous sampling data obtained in Step 1; Step 3: Perform periodic identification on the sorted and coordinate-matched full waveform data obtained in Step 2 to obtain the data with periodic alignment. Step 4: Superimpose positive and negative square waves on the period-aligned data obtained in Step 3, using a relative distance weighting method in space, to finally obtain optimized data with higher quality and accuracy; including the following sub-steps: Step 41: Superimpose positive and negative square waves on the period-aligned data obtained in Step 3 to obtain the superimposed data. Step 42: Perform relative distance weighted superposition on the data obtained in Step 41 after superimposing positive and negative square waves for each cycle to obtain the superimposed dense sampling data.

[0006] Furthermore, in step 1, the ground-to-air transient electromagnetic exploration system includes a transmitter, an unmanned aerial vehicle (UAV) platform, and a receiver. The transmitter is used to periodically provide alternating positive and negative trapezoidal current to a grounded long conductor or return source. The waveform of the trapezoidal current includes a rising edge, a continuous edge, a falling edge, and a power-off period. The receiver on the UAV platform is used to collect the induced electromotive force data of the rising edge, continuous edge, falling edge, and power-off period of the trapezoidal current using a full waveform linear recording method to obtain continuous sampling data.

[0007] Furthermore, in step 2, the data collected by the receiver of the UAV platform is sorted sequentially according to the preset survey lines and points in the survey area, so that the data collected multiple times at different times can be matched with the coordinates of the preset sampling points in the survey area, and the sorted and coordinate matched full waveform data is obtained.

[0008] Furthermore, in step 3, the full waveform data obtained after sorting and coordinate matching in step 2 is used with the response feature point at the instant of ground-to-air transient electromagnetic shutdown as the starting point of the complete cycle. Invalid periodic data is removed to ensure that the continuous sampling data on the entire measurement line has a complete cycle, and each cycle has four complete stages: rising edge, continuous edge, falling edge, and power-off period, to obtain the data after cycle alignment.

[0009] Furthermore, in step 41, the positive square wave in each period of the period-aligned data is subtracted from the negative square wave in that period and divided by 2 to obtain the superimposed data of the positive and negative square waves in each period, and the corresponding dense sampling attenuation curve for each period is obtained from the data.

[0010] Furthermore, step 42 includes the following process: Step 421, the th continuous sampling data X i Each sampled data Within the footprint area D, there is n sampling points ( For the j-th sampling point Its relative The distance is defined as: (1) The footprint range D is determined based on the actual number of times it needs to be superimposed; Step 422, Define Other sampling points within the footprint range D The relative distance weight is equal to distance The reciprocal of, as in equation (2): (2); Step 423, calculate the weighted sum of the relative distances within the footprint range D. ; Step 424: Normalize the relative distance weights for each data point: (3); Step 425: Perform relative distance weighted stacking to obtain the stacked dense sampling data. As in equation (4): (4); The data from each sampling point are superimposed according to the above-described moving footprints to obtain the superimposed dense sampling data; Step 426: Move the footprints sequentially according to the preset point spacing to complete the data superposition of each measuring point in the entire area.

[0011] Furthermore, the footprint range D is 1 times the preset point spacing.

[0012] Compared with the prior art, the present invention has the following technical effects: The method of this invention utilizes continuous sampling of full-waveform data from ground-to-air transient electromagnetic (GTE) data. By employing a moving footprint superposition technique, it suppresses electromagnetic noise components in the observed signals, thereby ensuring the exploration accuracy of the GTE method. Compared to existing technologies, this invention addresses the issue of coordinate matching and period misalignment in continuous sampling data during implementation. It utilizes a weighted approach to achieve temporal and spatial superposition of GTE data, improving the signal-to-noise ratio of GTE field data. The method of this invention is applicable to the preprocessing of continuous sampling data in all GTE exploration.

[0013] In summary, this invention improves the accuracy of data collected by the ground-to-air transient electromagnetic system by sorting, matching coordinates, aligning periods, and superimposing data collected multiple times by the UAV signal receiving system using weighted superposition technology. Attached Figure Description

[0014] Figure 1 A schematic diagram of a ground-to-air transient electromagnetic detection system; Figure 2 A trajectory diagram of data acquisition for a ground-to-air transient electromagnetic system; Figure 3 A schematic diagram of continuously sampled data with misaligned periods; Figure 4 This is a schematic diagram of continuously sampled data after periodic alignment; Figure 5 This is a schematic diagram of continuous sampling data after the superposition of positive and negative square waves; Figure 6 A schematic diagram of ground-to-air transient electromagnetic single-point data after overlay processing of moving footprints; Figure 7 This is a ground-to-air transient electromagnetic multi-track map after overlay processing of moving footprints.

[0015] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0016] The specific embodiments of the present invention will be further described with reference to the accompanying drawings. It should be noted that all devices used in the present invention are those known in the art. Embodiments of the present invention are given below.

[0017] Example The method for superimposing moving footprints of continuous sampling data of ground-to-air transient electromagnetic full waveforms given in this embodiment specifically includes the following steps: Step 1: Use a ground-to-air transient electromagnetic exploration system for signal transmission and reception.

[0018] like Figure 1 As shown, the air-to-ground transient electromagnetic exploration system adopts a common air-to-ground transient electromagnetic exploration system in this field (in this embodiment, the AirTem124SD model is selected), including a transmitter, an unmanned aerial vehicle (UAV) platform, and its receiver. Wherein: The transmitter is used to periodically provide alternating positive and negative trapezoidal current to a grounded long conductor or return source. The waveform of the trapezoidal current includes rising edge, continuous edge, falling edge, and power-off period. The receiver on the UAV platform is used to collect the rising edge, continuous edge, falling edge, and induced electromotive force data during the power-off period of the trapezoidal wave current using a full waveform linear recording method, thus obtaining continuous sampling data.

[0019] Step 2: Sort and match the coordinates of the continuous sampling data obtained in Step 1.

[0020] The data collected by the UAV platform's receiver is sorted sequentially according to the pre-defined survey lines and points within the survey area. This allows data collected multiple times at different times to be matched with the coordinates of the pre-defined sampling points within the survey area, resulting in sorted and coordinate-matched full waveform data. The data acquisition trajectory after sorting and coordinate matching for the ground-to-air transient electromagnetic field is shown below. Figure 2 As shown, the continuous sampling data collected in step 1 is as follows: Figure 3 As shown.

[0021] Step 3: Perform periodic identification on the sorted and coordinate-matched full waveform data obtained in Step 2 to obtain periodically aligned data.

[0022] The sorted and coordinate-matched full waveform data obtained in step 2 is used with the response characteristic point at the instant of ground-to-air transient electromagnetic shutdown as the starting point of the complete cycle. Invalid periodic data is removed to ensure that the continuous sampling data along the entire measurement line has a complete cycle, and that each cycle has four complete stages: rising edge, duration, falling edge, and the power outage period. This results in cycle-aligned data, such as... Figure 4 As shown.

[0023] Step 4: The period-aligned data obtained in Step 3 is superimposed with positive and negative square waves. The superposition is performed using a relative distance weighting method in space, and finally, optimized data with higher quality and accuracy is obtained.

[0024] Step 41: Superimpose positive and negative square waves on the period-aligned data obtained in Step 3 to obtain the superimposed data.

[0025] Specifically, the process involves subtracting the negative square wave from the positive square wave in each period of the periodically aligned data and dividing by 2 to obtain the superimposed data of the positive and negative square waves in each period. This data is then used to derive the corresponding dense sampling attenuation curve for each period. Figure 5 As shown; Step 42 involves performing relative distance-weighted superposition on the data obtained in Step 41 after superimposing the positive and negative square waves of each cycle, resulting in superimposed densely sampled data. This includes the following process: Step 421, the i-th sampled data in the superimposed data X of each period of positive and negative square waves obtained in step 41. There are n sampling points within the footprint range D ( For the j-th sampling point Its relative The distance is defined as: (1) The footprint range D is determined according to the actual number of times it needs to be superimposed. In this embodiment, D is 1 times the preset point distance.

[0026] Step 422, Define Other sampling points within the footprint range D The relative distance weight is equal to distance The reciprocal of, as in equation (2): (2); Step 423, calculate the weighted sum of the relative distances within the footprint range D. .

[0027] Step 424: Normalize the relative distance weights for each data point: (3); Step 425: Perform relative distance weighted stacking to obtain the stacked dense sampling data. As in equation (4): (4).

[0028] The data from each sampling point are superimposed according to the aforementioned moving footprints to obtain the superimposed dense sampling data, such as... Figure 6 As shown.

[0029] Step 426: Move the footprints sequentially according to the preset point spacing to complete the data superposition of each measuring point in the entire area, obtaining the ground-to-space transient electromagnetic response of the entire exploration area that can be used for inversion imaging. The data after superposition of all measuring points is as follows: Figure 7 As shown.

[0030] Figure 6 and Figure 7 The middle part is the attenuation curve and multi-channel curve formed by superimposing the continuous sampling data of the ground-to-air transient electromagnetic full waveform onto the moving footprints. Figure 6 , Figure 7 It can be seen that the attenuation curve is smooth overall, and the multi-channel curves have strong lateral continuity, indicating that this technology can significantly improve the quality of ground-to-air transient electromagnetic field data.

Claims

1. A method for moving footprint stacking of ground-air transient electromagnetic full waveform continuous sampling data, characterized in that, Specifically, the steps include the following: Step 1: Use a ground-to-air transient electromagnetic exploration system for signal transmission and reception; Step 2: Sort and match the coordinates of the continuous sampling data obtained in Step 1; Step 3: Perform periodic identification on the sorted and coordinate-matched full waveform data obtained in Step 2 to obtain periodically aligned data; Step 4: Superimpose positive and negative square waves on the period-aligned data obtained in Step 3, using a relative distance weighting method in space, to finally obtain optimized data with higher quality and accuracy; including the following sub-steps: Step 41: Superimpose positive and negative square waves on the period-aligned data obtained in Step 3 to obtain the superimposed data. Step 42 involves performing relative distance-weighted superposition on the data obtained in Step 41 for each period of positive and negative square waves, resulting in superimposed densely sampled data; this includes the following process: Step 421, the jth sampling data in the continuous sampling data X i There are n sampling points in the footprint range D , for the jth sampling point in it, the distance relative to is defined as:​ （1） The footprint range D is determined based on the actual number of times it needs to be superimposed; Step 422, define the relative distance weight of other sampling points within the footprint range D is equal to the inverse of the distance , as formula (2): ​ （2）； Step 423, calculate the weighted sum of the relative distances within the footprint range D. ; Step 424: Normalize the relative distance weights for each data point: （3）； Step 425: Perform relative distance weighted stacking to obtain the stacked dense sampling data. As in equation (4): （4）； The data from each sampling point are superimposed according to the aforementioned moving footprints to obtain the superimposed dense sampling data; Step 426: Move the footprints sequentially according to the preset point spacing to complete the data superposition of each measuring point in the entire area.

2. The method for superimposing moving footprints from ground-to-air transient electromagnetic full-waveform continuous sampling data as described in claim 1, characterized in that, In step 1, the ground-to-air transient electromagnetic exploration system includes a transmitter, an unmanned aerial vehicle (UAV) platform, and a receiver. The transmitter is used to periodically provide alternating positive and negative trapezoidal current to a grounded long conductor or return source. The waveform of the trapezoidal current includes a rising edge, a continuous edge, a falling edge, and a period of power failure. The receiver on the UAV platform is used to collect the induced electromotive force data of the rising edge, continuous edge, falling edge, and power failure period of the trapezoidal current using a full waveform linear recording method to obtain continuous sampling data.

3. The method for superimposing moving footprints from ground-to-air transient electromagnetic full-waveform continuous sampling data as described in claim 2, characterized in that, In step 2, the data collected by the receiver of the UAV platform is sorted according to the pre-set survey lines and points in the survey area, so that the data collected multiple times at different times can be matched with the coordinates of the pre-set sampling points in the survey area, and the sorted and coordinate matched full waveform data is obtained.

4. The method for superimposing moving footprints from ground-to-air transient electromagnetic full-waveform continuous sampling data as described in claim 2, characterized in that, In step 3, the full waveform data obtained after sorting and coordinate matching in step 2 is used with the response feature point at the instant of ground-to-air transient electromagnetic shutdown as the starting point of the complete cycle. Invalid periodic data is removed to ensure that the continuous sampling data on the entire measurement line has a complete cycle, and each cycle has four complete stages: rising edge, continuous edge, falling edge, and power-off period, to obtain the data after cycle alignment.

5. The method for superimposing moving footprints of continuous sampling data of ground-to-air transient electromagnetic full waveform as described in claim 2, characterized in that, In step 41, specifically, the positive square wave in each period of the period-aligned data is subtracted from the negative square wave in that period and divided by 2 to obtain the data after the positive and negative square waves are superimposed in each period, and the dense sampling attenuation curve corresponding to each period is obtained from the data.

6. The method for superimposing moving footprints from ground-to-air transient electromagnetic full-waveform continuous sampling data as described in claim 2, characterized in that, The footprint range D is 1 times the preset point spacing.

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