A method for correcting multi-transmitter inter-frame ground-air transient electromagnetic data

Abstract

The application relates to the field of electromagnetic exploration, in particular to a multi-transmit-frame ground-air transient electromagnetic data correction method, which comprises the following steps: for a plurality of transmit frames pre-arranged in a target exploration range, all detection points corresponding to each transmit frame are paired and collected, including a primary field measured field value in a transmit waveform falling edge period and secondary field response data in a pure induction period after the transmit waveform is turned off; the maximum value of the primary field of all detection points in the target exploration range is determined; the ratio between the maximum value of the primary field and the measured field value of each detection point is taken as an excitation correction coefficient of each detection point; the secondary field response data of the corresponding detection point is corrected by using the excitation correction coefficient of each detection point, so that standard secondary field data are obtained. The global maximum value of the measured primary field in the transmit waveform falling edge period is taken as a unified reference to correct the secondary field data point by point, so that the consistency fusion of the multi-transmit-frame ground-air transient electromagnetic data is realized.

Description

Technical Field

[0001] This application relates to the field of electromagnetic exploration, and more specifically, to a method for correcting ground-space transient electromagnetic data between multiple emission frames. Background Technology

[0002] Ground-to-air transient electromagnetic detection technology is a geophysical exploration technique that combines a ground-based transmitting line with an airborne receiving device. It boasts advantages such as large detection depth, strong terrain adaptability, high efficiency, and good resolution, and is widely used in mineral resource exploration, geological hazard investigation, underground cavity detection, and hydrogeological surveys. The core principle of this technology is as follows: a primary pulse electromagnetic field is transmitted underground via a ground-based transmitting line. After the pulse is turned off, the underground geological body generates a secondary eddy current field due to electromagnetic induction. The airborne receiving device collects the secondary field response data, and by analyzing the characteristics of the secondary field data, the electrical structure, spatial distribution, and morphological features of the underground geological body can be inverted.

[0003] Currently, mainstream loop-source ground-to-air transient electromagnetic transmission systems have inherent coverage limitations; the effective uniform electromagnetic field coverage area of ​​a single transmission loop is typically less than 1 square kilometer. In large-area, wide-scale field exploration and construction scenarios, the target detection area often far exceeds the effective coverage of a single transmission frame. Therefore, the industry generally adopts a zoned frame construction mode, which divides the overall working area into several interconnected and partially overlapping sub-regions. Each sub-region corresponds to an independent transmission frame to complete one field excitation and data acquisition operation. Finally, the detection data from multiple sub-regions are stitched together to form the overall detection result.

[0004] However, this construction method has a core technical flaw: the primary electromagnetic field generated by the rectangular ground-based transmission loop exhibits significant spatial non-uniformity. The electromagnetic field intensity is high and uniform in the central region of the transmission frame, while the intensity at the edges and offset regions decays rapidly and is severely distorted. The locations and coverage areas of the transmission frames differ across sub-regions, resulting in completely different primary field excitation intensities and field distribution characteristics for each frame. This leads to systematic deviations in the secondary field response data collected from different transmission frames at the same geological location, resulting in inconsistent data magnitudes and curve shapes across multiple transmission frames and a serious problem of data inconsistency between frames.

[0005] The aforementioned data deviations cannot be eliminated by conventional filtering, denoising, baseline correction, and other preprocessing methods. This directly leads to the failure of multi-frame data splicing and poor uniformity of data across the entire domain, significantly reducing the accuracy of subsequent data inversion and geological interpretation. It is also prone to problems such as false anomalies, anomaly misalignment, and signal distortion, which greatly limits the application of ground-to-air transient electromagnetic technology in large-area, high-precision exploration scenarios.

[0006] Regarding the aforementioned issue of inconsistent transient electromagnetic data across multiple emitter frames, the mainstream correction schemes in the industry and their existing shortcomings are as follows: (1) Mean adjustment correction method for overlapping regions This method, currently the most commonly used existing technology, involves using repeated detection data from overlapping areas of adjacent launch frames to calculate the mean deviation of the overlapping area data and then performing a unified adjustment correction on the overall data. However, this method can only correct random deviations caused by construction noise and equipment errors, and cannot identify or eliminate systematic deviations caused by primary field spatial inhomogeneities. Furthermore, the overlapping area data is easily affected by local underground anomalies and terrain interference, resulting in poor stability of the adjustment results. It completely fails in multi-launch frame detection scenarios without overlapping areas, exhibiting low correction accuracy and poor adaptability.

[0007] (2) Numerical simulation field source correction method This method constructs a numerical simulation model of the electromagnetic field of the emission loop, simulates and calculates the theoretical intensity of the primary field at different locations, and corrects the measured secondary field data based on the theoretical field values. However, this method has obvious limitations: the numerical simulation model is an ideal homogeneous model, which cannot match actual working conditions such as complex terrain in the field, non-uniform electrical properties of the strata, and deformation of the emission loop. The simulated field values ​​deviate significantly from the actual excitation field values, and significant residual errors still exist after correction. At the same time, the numerical simulation is computationally intensive and extremely inefficient, making it unsuitable for large-scale batch processing of field exploration data.

[0008] (3) Overall normalization correction method This method achieves data uniformity by performing global extreme value normalization on the secondary field data of all transmitter frames. However, this method only performs numerical scaling of the data and does not take into account the essential characteristics of the field source excitation. It cannot eliminate the signal distortion caused by the differences in primary field excitation between different transmitter frames, which will destroy the geological response characteristics of the original secondary field, resulting in the loss of real geological anomaly information and seriously affecting the reliability of subsequent geological interpretation.

[0009] In summary, none of the existing technologies have proposed a solution to the core problem of uneven primary field excitation in multiple emitter frames. They generally suffer from defects such as low correction accuracy, poor adaptability, easy loss of effective mass signals, and low computational efficiency. They cannot achieve high-precision consistency correction of multi-emitter frame data and cannot meet the engineering requirements of large-area high-precision ground-to-air transient electromagnetic exploration. Summary of the Invention

[0010] In view of this, this application provides a ground-to-space transient electromagnetic data correction method between multiple transmitter frames to overcome the shortcomings of existing ground-to-space transient electromagnetic data correction technologies for multiple transmitter frames, and to solve the problem that existing technologies cannot eliminate the secondary field data system deviation caused by the uneven spatial distribution of the primary field of the transmitter frames and the inconsistent excitation conditions of multiple transmitter frames.

[0011] The technical solution provided in this application is as follows: A method for correcting ground-to-space transient electromagnetic data between multiple transmission frames, comprising: For multiple pre-deployed transmission frames within the target exploration area, all detection points corresponding to each transmission frame are paired and collected, including the primary field measured value during the falling edge of the transmission waveform and the secondary field response data during the pure induction period after the transmission waveform is turned off. Determine the maximum value of the first field at all detection points within the target exploration range; The ratio between the maximum value of the primary field and the measured value of the primary field at each detection point is used as the excitation correction coefficient for each detection point. The secondary field response data of the corresponding detection points are corrected by using the excitation correction coefficients of each detection point to obtain standard secondary field data.

[0012] In one possible implementation, the multiple launch frames within the target exploration range are rectangular launch loops; the multiple launch frames are arranged in an overlapping area or a non-overlapping arrangement.

[0013] In one possible implementation, the pairing and acquisition of the primary field measured value and the secondary field response data of each detection point is performed by an aerial receiving device, which includes an unmanned aerial vehicle platform, a receiver, and a receiving coil.

[0014] In one possible implementation, the transmitted waveform is a bipolar trapezoidal wave, which includes a forward power supply phase and a reverse power supply phase. The positive power supply phase includes rising edge, power supply, falling edge, and power off. The falling edge is the turn-off transition phase, and the measured field value during the falling edge period is used to reflect the true excitation field strength of the corresponding detection point.

[0015] In one possible implementation, the standard secondary field data corresponding to each detection point is represented as the product of the secondary field response data corresponding to each detection point and the excitation correction coefficient.

[0016] In one possible implementation, after correcting the secondary field response data of each detection point, the method further includes: All corrected standard secondary field data are integrated into a unified global dataset for data inversion and global imaging of underground geological bodies.

[0017] Compared with the prior art, the technical solution provided in this application has the following beneficial effects: (1) For the first time, the inherent physical law that the measured primary field value and the secondary field response value are linearly proportional at the falling edge of the transmitted waveform is utilized to take the measured primary field value as the core benchmark for secondary field data correction, thereby solving the problem of inconsistent data in multiple transmission frames from the perspective of field source excitation.

[0018] (2) The innovative approach of synchronously pairing the primary field observation during the falling edge and the secondary field during the pure off period ensures that the primary field data is free from underground geological signal interference, accurately reflects the true excitation field strength at the measuring point, and provides a reliable data basis for high-precision calibration.

[0019] (3) Using the maximum value of the primary field in the whole domain as a unified benchmark, construct point-by-point quantization correction coefficients to achieve standardization and consistency correction of secondary field data in different launch frames and different spatial locations, taking into account both data fidelity and whole-domain uniformity.

[0020] (4) No need for overlapping area support of the launch frame, adaptable to any partition layout mode and complex field conditions, and realizes multi-launch frame data fusion correction without dead angles and with high precision. Attached Figure Description

[0021] Figure 1 This is a flowchart of a multi-transmitter frame ground-to-space transient electromagnetic data correction method provided in Embodiment 1 of this application.

[0022] Figure 2 This is a schematic diagram of the ground-to-air transient electromagnetic emission waveform provided in Embodiment 1 of this application.

[0023] Figure 3 This is a diagram of the ground-to-air transient electromagnetic multi-emission frame detection device provided in Embodiment 1 of this application. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0025] Example 1 See Figure 1 This is a flowchart of a multi-transmitter frame ground-to-space transient electromagnetic data correction method provided in Embodiment 1 of this application. Figure 1 As shown, the specific implementation steps of the above method include: Step 101: For the multiple pre-deployed transmitting frames within the target exploration range, pair and collect all the detection points corresponding to each transmitting frame, including the primary field measured value during the falling edge of the transmitted waveform and the secondary field response data during the pure induction period after the transmitted waveform is turned off.

[0026] In this embodiment, the entire detection area is divided into several continuous and connected sub-detection areas based on the target exploration area and the effective coverage area of ​​a single transmitter frame. Rectangular transmitter loops (transmitter frames) are independently deployed for each sub-area, and construction parameters such as the deployment coordinates, side length, transmission current, and position attitude of each transmitter frame are recorded. All sub-areas are fully covered without omission, and a small number of overlapping areas or non-overlapping deployments can be set according to construction needs.

[0027] Furthermore, a ground-to-air transient electromagnetic synchronous acquisition mode is adopted for the sub-region corresponding to each transmitting frame. A bipolar trapezoidal wave transmission current is applied to the ground transmitting frame. For example... Figure 2 As shown, the bipolar trapezoidal wave includes a forward power supply phase and a reverse power supply phase. The forward power supply phase includes the rising edge, power supply, falling edge, and power outage. During the falling edge of the transmitted waveform, there is no underground secondary field interference, and the acquired primary field value is the true excitation field strength of the transmitting source at that measuring point, accurately reflecting the actual excitation energy at that point and unaffected by the electrical characteristics of underground geological bodies.

[0028] Therefore, this application collects the primary field values ​​at each detection point during the falling edge of the transmitted waveform (the turn-off transition phase). B 1. During the pure induction period after the transmitted waveform is completely turned off, the secondary field response data B2 of the corresponding measurement point is collected. All measurement points complete the pairing acquisition of primary and secondary fields at the same location and in the same sequence to ensure that the two sets of data are completely corresponding in spatial and temporal dimensions.

[0029] In some embodiments, the pairing and acquisition of primary field measured values ​​and secondary field response data at each detection point is performed by an air-to-air receiving device. For example... Figure 3 As shown, the airborne receiving equipment is a transient electromagnetic airborne receiving system based on an unmanned aerial vehicle (UAV) system, including an UAV platform, a receiver, and a receiving coil.

[0030] Step 102: Determine the maximum value of the primary field at all detection points within the above target exploration range.

[0031] Step 103: Use the ratio between the maximum value of the primary field and the measured value of the primary field at each detection point as the excitation correction coefficient for each detection point.

[0032] Specifically, based on the physical relationship that the primary field and the secondary field are linearly proportional, the maximum value of the primary field is selected from all transmitting frames and all measuring points in the entire domain. B 1max This serves as a unified reference field value. For each detection point, the excitation correction coefficient for that detection point is calculated. K , represented as: K = B 1max / B1i In the formula, B 1i Indicates the first i The measured field value at each measuring point. K This represents the excitation correction coefficient for the corresponding detection point.

[0033] This correction coefficient can accurately characterize the field strength difference of each measuring point relative to the optimal excitation reference in the whole domain, and fully quantify the non-uniform deviation of the primary field excitation at different firing frames and different spatial positions.

[0034] Step 104: Correct the secondary field response data of the corresponding detection points using the excitation correction coefficients of each detection point to obtain standard secondary field data.

[0035] Specifically, the secondary field response data of each detection point is corrected using the excitation correction coefficients of each detection point to obtain the corrected standard secondary field data. B 2 std , represented as: B 2 std = B 2i × K In the formula, B 2i Indicates the first i The original secondary field response data of each measuring point B 2 std This represents the secondary field data of the unified reference after correction.

[0036] In this embodiment, all measurement points covered by all transmitter frames are traversed to complete the point-by-point correction of all secondary field data. All corrected standard secondary field data are integrated into a unified dataset for the entire domain, eliminating system data deviations between multiple transmitter frames, achieving benchmark unification and data comparability of detection data from different transmitter frames and different locations, and completing the consistency correction of ground-to-air transient electromagnetic data between multiple transmitter frames.

[0037] The corrected global data benchmark is unified and highly comparable, completely solving problems such as misalignment of multi-frame data splicing, false anomalies, and data discontinuity. It significantly improves the accuracy of transient electromagnetic data inversion and global imaging effect, providing high-quality data support for large-area geological exploration, resource evaluation, and disaster detection.

[0038] Compared with the prior art, the technical solution provided in Embodiment 1 of this application has the following beneficial effects: (1) Eliminates multi-emission frame data deviation from the root cause, with extremely high correction accuracy. This application abandons the indirect correction method of existing technologies that rely on simulated data and overlapping area data. Instead, it directly collects the actual measured values ​​of the primary field at each measurement point as the correction benchmark, accurately quantifies the excitation inhomogeneity of different emitter frames and different positions, eliminates the secondary field system deviation from the root cause of the primary field excitation difference, and completely solves the problem of inconsistent data among multiple emitter frames. The correction accuracy is far higher than that of traditional adjustment methods and numerical simulation methods.

[0039] (2) It fully preserves the effective quality signal, and the data reliability is strong. This application performs correction based on the inherent physical proportional relationship between the primary and secondary fields. It only eliminates the systematic errors caused by field source excitation, without changing the underground geological response characteristics corresponding to the secondary field data. It fully preserves the effective signals of underground anomalies and changes in the electrical properties of strata, avoiding problems such as signal distortion and anomaly loss caused by traditional normalization correction and simulation correction, and significantly improving the accuracy of subsequent geological interpretation.

[0040] (3) Wide adaptability, no construction conditions restrictions This application does not rely on the overlapping area data of the transmitter frame, supports arbitrary partitioning construction modes with or without overlap, and is suitable for complex terrain and large-scale full-domain exploration scenarios. It is not affected by actual field conditions such as transmitter loop deformation, small current fluctuations, and uneven strata, and has strong robustness. It is applicable to all loop source ground-to-space transient electromagnetic detection systems.

[0041] (4) High computational efficiency, suitable for batch engineering applications The correction algorithm in this application is simple and logically clear. It does not require complex numerical simulation modeling and massive iterative calculations. It can complete the correction by performing point-by-point calculations on measured data. The calculation speed is fast, which can realize the automated and rapid correction of large batches of field exploration data and fully meet the needs of engineering and large-scale applications.

[0042] (5) Improve the quality of exploration results across the entire region The corrected global data benchmark is unified and highly comparable, completely solving problems such as misalignment of multi-frame data splicing, false anomalies, and data discontinuity. It significantly improves the accuracy of transient electromagnetic data inversion and global imaging effect, providing high-quality data support for large-area geological exploration, resource evaluation, and disaster detection.

[0043] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for correcting ground-to-space transient electromagnetic data between multiple transmission frames, characterized in that, include: For multiple pre-deployed transmitting frames within the target exploration area, all detection points corresponding to each transmitting frame are paired and collected, including the primary field measured value during the falling edge of the transmitted waveform and the secondary field response data during the pure induction period after the transmitted waveform is turned off. Determine the maximum value of the first field at all detection points within the target exploration range; The ratio between the maximum value of the primary field and the measured value of the primary field at each detection point is used as the excitation correction coefficient for each detection point. The secondary field response data of the corresponding detection points are corrected by using the excitation correction coefficients of each detection point to obtain standard secondary field data.

2. The multi-transmitter inter-frame ground-to-space transient electromagnetic data correction method according to claim 1, characterized in that, The multiple launch frames within the target exploration area are rectangular launch loops; the multiple launch frames are arranged in either overlapping or non-overlapping areas.

3. The multi-transmitter inter-frame ground-to-space transient electromagnetic data correction method according to claim 1, characterized in that, The pairing and acquisition of primary field measured values ​​and secondary field response data at each detection point is performed by an aerial receiving device, which includes an unmanned aerial vehicle platform, a receiver, and a receiving coil.

4. The multi-transmitter inter-frame ground-to-space transient electromagnetic data correction method according to claim 1, characterized in that, The transmitted waveform is a bipolar trapezoidal wave, which includes a forward power supply phase and a reverse power supply phase. The positive power supply phase includes rising edge, power supply, falling edge, and power off. The falling edge is the turn-off transition phase, and the measured field value during the falling edge period is used to reflect the true excitation field strength of the corresponding detection point.

5. A method for correcting ground-to-space transient electromagnetic data between multiple transmission frames according to claim 1, characterized in that, The standard secondary field data corresponding to each detection point is represented as the product of the secondary field response data corresponding to each detection point and the excitation correction coefficient.

6. The multi-transmitter inter-frame ground-to-space transient electromagnetic data correction method according to claim 1, characterized in that, After correcting the secondary field response data of each detection point, the method further includes: All corrected standard secondary field data are integrated into a unified global dataset for data inversion and global imaging of underground geological bodies.

Images