A three-dimensional transient electromagnetic survey system

Abstract

The application discloses a three-dimensional transient electromagnetic measurement system, and relates to the technical field of geophysical prospecting, which comprises a transmitting subsystem, a receiving subsystem and a data processing subsystem, and is integrated on a vehicle platform; the transmitting subsystem is used for transmitting transient electromagnetic signals generated by a transmitting coil to each receiving coil; the receiving subsystem is used for receiving electromagnetic signals generated by each receiving coil; and the data processing subsystem is used for processing the received electromagnetic signals to obtain a three-dimensional electrical structure of the underground. The application adopts the transient electromagnetic method with high penetration capacity in near-surface detection, realizes three-dimensional detection and three-dimensional imaging of the near-surface target, solves the problem of difficult interpretation of the two-dimensional transient electromagnetic resistivity image, improves the imaging and interpretation accuracy of the three-dimensional target of the underground, and realizes high-precision detection of the near-surface.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration technology, and in particular relates to a three-dimensional transient electromagnetic measurement system. Background Technology

[0002] Transient electromagnetic methods (TEM) detect underground electrical structures by emitting transient electromagnetic fields and receiving induced signals. Traditional methods are mostly ground-based fixed measurements, resulting in low efficiency and insufficient spatial resolution. While two-dimensional vehicle-mounted TEM systems improve efficiency, they still have limitations in three-dimensional data acquisition and processing. Ground-penetrating radar (GPR) and TEM are the most important methods for efficient near-surface exploration. Three-dimensional GPR technology has wide applications in near-surface exploration due to its high resolution and efficient data acquisition. However, GPR has a shallow detection depth, making it difficult to detect targets at greater depths. Transient electromagnetic methods use relatively low-frequency electromagnetic waves to probe underground media in the time domain, achieving relatively greater penetration depth. The basic principle of TEM detection is to apply a pulsed current to a transmitting coil to generate a transient electromagnetic field, which in turn generates a secondary induced eddy current field in the underground medium. During the interval between the primary pulses, the receiving coil records the changes in induced voltage or induced magnetic field, and measures the attenuation characteristics of the secondary induced eddy current field, thereby acquiring underground geological information and imaging the underground medium. To recover the impulse response, a high-power multi-channel transient electromagnetic system simultaneously records the transmitted waveform and the ground response. The high-power multi-channel transient electromagnetic data is then interpreted based on the extracted ground impulse response. Supported by a major national scientific research and equipment development project, the research on the high-power multi-channel transient electromagnetic system has been completed, and the system is currently undergoing field testing. The transmitter system consists of a generator, an uncontrolled rectifier bridge, a pulse width modulation DC / DC full-bridge converter, an H-inverter bridge, and a mode generator capable of producing PRBS signals. The acquisition station has a dynamic range of 160 dB, a minimum detectable voltage of 50 nV, a synchronization accuracy of 5 μs, a sampling rate of 16 Ksps, and data transmission is based on the TCP / IP protocol. The high-power multi-channel transient electromagnetic system transmits the PRBS signal to the ground via a grounding wire, simultaneously recording the electromagnetic field response and the current transmitted over land. The Earth's impulse response can be obtained through deconvolution, and the subsurface resistivity value is ultimately calculated to reconstruct the subsurface resistivity distribution and locate the desired geological targets.

[0003] However, in urban applications, conventional transient electromagnetic systems have large coils and are susceptible to numerous interference factors; the limited space for ground-based detection in urban areas also makes measurement work difficult. Existing technologies have also proposed towed transient electromagnetic technology for acquiring and imaging transient electromagnetic data from urban roads, but this is a single-transmitter, single-receiver system, resulting in significant ambiguity in data interpretation and making the identification of potential underground hazards difficult. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a three-dimensional transient electromagnetic measurement system. Addressing the issues of shallow detection depth in three-dimensional ground-penetrating radar and the difficulty in target identification and low efficiency in forming three-dimensional detection using traditional two-dimensional transient electromagnetic methods, this system employs a transient electromagnetic method with high penetration capability in near-surface detection. This enables three-dimensional detection and imaging of near-surface targets, solving the problem of difficult interpretation of two-dimensional transient electromagnetic resistivity images, improving the imaging and interpretation accuracy of underground three-dimensional targets, and achieving high-precision near-surface detection.

[0005] To achieve the above objectives, the present invention provides a three-dimensional transient electromagnetic measurement system, comprising:

[0006] The system comprises a transmitting subsystem, a receiving subsystem, and a data processing subsystem, all integrated into the vehicle platform.

[0007] The transmitting subsystem is used to transmit transient electromagnetic signals generated by the transmitting coil to each receiving coil;

[0008] The receiving subsystem is used to receive electromagnetic signals generated by each receiving coil;

[0009] The data processing subsystem is used to process the received electromagnetic signals to obtain the underground three-dimensional electrical structure.

[0010] Optionally, the transmitting subsystem includes a power module, a GPS receiving module, a wireless transceiver module, a display module, a status monitoring module, and a control module;

[0011] The power module is used to power itself and the transmitting and receiving coils;

[0012] The GPS receiving module is used to receive satellite synchronization signals, process them, and obtain the latitude and longitude information and PPS second pulse signal of the target area.

[0013] The wireless transceiver module is used for wireless communication between the control module and the host.

[0014] The display module is used to connect to the control module and display the status of the host;

[0015] The status monitoring module is used to detect the status of the overall system;

[0016] The control module is used to sample the current of the transmitting coil through a current sensor to obtain a voltage signal that is proportional to the current. After passing through the corresponding filtering and amplification circuits, the signal enters the high-speed ADC and is processed by the FPGA to obtain the current sample.

[0017] Optionally, the power module includes a low-voltage unit and a high-voltage unit;

[0018] The low-voltage unit is used for the instrument's own power supply loop. The energy comes from the internal 12V lithium battery or the external 12V lithium battery. After passing through the selector, it enters the DC-DC conversion circuit in the power controller to obtain the different operating voltages required by the instrument.

[0019] The high-voltage unit is an energy loop used to power the coil. The energy comes from the external power supply input port of the transmitting coil, and after passing through the overcurrent protection circuit and the overvoltage protection circuit, it enters the H-bridge. The H-bridge drive module provides a suitable IGBT drive waveform to drive the H-bridge, and then transmits it out through the transmitting coil.

[0020] Optionally, the GPS receiving module includes: a GPS antenna, an LNA amplifier, and a controller, wherein after the GPS antenna receives the synchronization signal from the satellite, it is preprocessed by the LNA amplifier to obtain the required latitude and longitude information and PPS second pulse signal.

[0021] Optionally, the wireless transceiver module includes an antenna and an LNA amplifier, wherein the antenna is bidirectionally connected to the LNA amplifier, the LNA amplifier is bidirectionally connected to the wireless transceiver module, and the wireless transceiver module is bidirectionally connected to the control module.

[0022] Optionally, the receiving subsystem includes a signal processing module, a GPS positioning module, and a control and measurement module;

[0023] The signal processing module is used to process the electromagnetic signal generated by the receiving coil to obtain the processed electromagnetic signal.

[0024] The GPS positioning module is used to perform secondary measurement positioning based on the acquired latitude and longitude information and PPS second pulse signal;

[0025] The control and measurement module is used to control the terminal equipment and parameter settings, and to perform tests and system measurements after confirming that the GPS signal is valid.

[0026] Optionally, the signal processing module includes a signal preprocessing unit, a signal amplification and filtering unit, and an ADC unit;

[0027] The signal preprocessing unit is used to preprocess the electromagnetic signal generated by the receiving coil to obtain the preprocessed electromagnetic signal.

[0028] The signal amplification and filtering unit is used to amplify and filter the preprocessed electromagnetic signal to obtain the filtered electromagnetic signal.

[0029] The ADC unit is used to digitally process the filtered electromagnetic signal to obtain a digital signal.

[0030] Optionally, the data processing subsystem includes a curve normalization unit, a three-dimensional data measurement unit, and a data imaging unit;

[0031] The curve normalization unit is used to collect data to obtain attenuation curves of channels 1-12, and normalize the attenuation curves according to the distribution of the primary field to obtain attenuation curve profiles of channels 1-12.

[0032] The three-dimensional data measurement unit is used to run the vehicle system, continuously measure and sample, and obtain three-dimensional measurement data by measuring the distance between measurement points along the vehicle's direction of travel.

[0033] The data imaging unit is used to image the attenuation curve shape and resistivity of the data to determine a three-dimensional image of the underground target.

[0034] Technical effects of the invention:

[0035] (1) In terms of detection efficiency: The single-transmitter-multiple-receiver data measurement mode is adopted, which improves the efficiency of field detection data acquisition, saves working time, and reduces detection costs compared with traditional two-dimensional measurement.

[0036] (2) Detection capability: Improve the detection capability of underground targets, provide a basis for three-dimensional imaging of underground targets and obtain the three-dimensional structure of the target body, and obtain more information on the underground structure;

[0037] (3) Detection effect: While ensuring the detection effect of two-dimensional structures, it provides better detection effect for three-dimensional geological structures, especially for isometric and linear targets;

[0038] (4) Anti-interference: Multiple receiving coils are used to reduce the interference caused by the presence of local metal objects under a single coil on the transient electromagnetic receiving signal. Attached Figure Description

[0039] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0040] Figure 1 This is a schematic diagram of the transmitting coil and receiving coil structure according to an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the overall vehicle-mounted system structure according to an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of a three-dimensional transient electromagnetic measurement system according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the transmission subsystem structure according to an embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the power module structure in the transmitting subsystem of an embodiment of the present invention;

[0045] Figure 6 This is a schematic diagram of the GPS receiving module structure in the transmitting subsystem of an embodiment of the present invention;

[0046] Figure 7 This is a schematic diagram of the wireless transceiver module structure in the transmitting subsystem of an embodiment of the present invention;

[0047] Figure 8 This is a schematic diagram of the display module structure in the transmitting subsystem of an embodiment of the present invention;

[0048] Figure 9 This is a schematic diagram of the status monitoring module structure in the launch subsystem of this invention.

[0049] Figure 10 This is a schematic diagram of the control module structure in the launch subsystem of an embodiment of the present invention;

[0050] Figure 11 This is a schematic diagram of the receiving subsystem structure according to an embodiment of the present invention;

[0051] Figure 12 This is a schematic diagram of the signal processing module structure in the receiving subsystem of this invention.

[0052] Figure 13 This is a schematic diagram of the GPS positioning module structure in the receiving subsystem of this invention.

[0053] Figure 14 This is a schematic diagram of the control and measurement module structure in the receiving subsystem of this invention. Detailed Implementation

[0054] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0055] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0056] like Figure 1As shown, this embodiment of a three-dimensional transient electromagnetic measurement system comprises four parts: a transmitting coil, a transmitter, a receiving coil, and a receiver. Multiple receiving coils are connected to a multichannel receiver, and the transmitting coil is connected to the transmitter, forming a one-to-many system. The transmitting coil has a rectangular structure with multiple turns (2-5 turns) wound; the receiving coil has a circular structure with multiple turns (10-30 turns) wound, and multiple sets are connected in series. The transmitting coil is placed at the rear end of the transmitting coil, and a compensation coil is used to counteract the strong signal influence of the primary field, reducing the blind zone of the received signal and increasing the effective signal length. Since the secondary induced field at different receiving positions has certain differences, the received signal needs further normalization. Figure 2 This is a schematic diagram of an onboard control system. Figure 1 The detection system is towed by a tractor, with a distance of 3-6 meters between the tractor and the transmitting coil to reduce interference from the tractor. The transmitting and receiving system is housed inside the tractor and is equipped with a GPS measurement and control system.

[0057] like Figure 3 As shown, this embodiment provides a three-dimensional transient electromagnetic measurement system, including:

[0058] The system comprises a transmitting subsystem, a receiving subsystem, and a data processing subsystem, all integrated into the vehicle platform.

[0059] The transmitting subsystem is used to transmit transient electromagnetic signals generated by the transmitting coil to each receiving coil;

[0060] The receiving subsystem is used to receive electromagnetic signals generated by each receiving coil;

[0061] The data processing subsystem is used to process the received electromagnetic signals to obtain the underground three-dimensional electrical structure.

[0062] Furthermore, the transmitting subsystem includes a power module, a GPS receiving module, a wireless transceiver module, a display module, a status monitoring module, and a control module;

[0063] The power module is used to power itself and the transmitting and receiving coils;

[0064] The GPS receiving module is used to receive satellite synchronization signals, process them, and obtain the latitude and longitude information and PPS second pulse signal of the target area.

[0065] The wireless transceiver module is used for wireless communication between the control module and the host.

[0066] The display module is used to connect to the control module and display the status of the host;

[0067] The status monitoring module is used to detect the status of the overall system;

[0068] The control module is used to sample the current of the transmitting coil through a current sensor to obtain a voltage signal that is proportional to the current. After passing through the corresponding filtering and amplification circuits, the signal enters the high-speed ADC and is processed by the FPGA to obtain the current sample.

[0069] Furthermore, the power module includes a low-voltage unit and a high-voltage unit;

[0070] The low-voltage unit is used for the instrument's own power supply loop. The energy comes from the internal 12V lithium battery or the external 12V lithium battery. After passing through the selector, it enters the DC-DC conversion circuit in the power controller to obtain the different operating voltages required by the instrument.

[0071] The high-voltage unit is an energy loop used to power the coil. The energy comes from the external power supply input port of the transmitting coil, and after passing through the overcurrent protection circuit and the overvoltage protection circuit, it enters the H-bridge. The H-bridge drive module provides a suitable IGBT drive waveform to drive the H-bridge, and then transmits it out through the transmitting coil.

[0072] Furthermore, the GPS receiving module includes a GPS antenna, an LNA amplifier, and a controller. After receiving the synchronization signal from the satellite, the GPS antenna is preprocessed by the LNA amplifier to obtain the required latitude and longitude information and PPS second pulse signal.

[0073] Furthermore, the wireless transceiver module includes an antenna and an LNA amplifier, wherein the antenna is bidirectionally connected to the LNA amplifier, the LNA amplifier is bidirectionally connected to the wireless transceiver module, and the wireless transceiver module is bidirectionally connected to the control module.

[0074] Specifically, such as Figure 4 As shown, the line terminal device connects to the transient electromagnetic system via a wireless module. Under the control of the control system, driven by the precise time signal from the GPS receiving system, the external transmitting coil is powered and converted into the required waveform by the power supply system and applied to the transmitting coil. The changing current is transmitted through the coil in the form of an electromagnetic field. Status monitoring monitors the operating status of each circuit in real time and provides real-time protection for the circuit.

[0075] like Figure 5As shown, the power module is divided into two parts: low-voltage and high-voltage. The low-voltage part is the instrument's own power supply loop, with energy sourced from an internal or external 12V lithium battery. After passing through a selector, it enters the DC-DC converter circuit within the power controller to obtain the different operating voltages required by the instrument. The high-voltage part is the power supply loop for the coil, with energy sourced from the external transmitting coil power input port. After passing through overcurrent and overvoltage protection circuits, it enters the H-bridge. The H-bridge driver module provides a suitable IGBT drive waveform to drive the H-bridge, and finally, the energy is transmitted through the transmitting coil. The transmitting coil provides a path for dissipating the transmitted energy of the transient electromagnetic instrument. A reasonable external transmitting coil power supply voltage is selected based on its internal resistance, theoretically based on a current not exceeding 80% of the instrument's maximum transmitting current.

[0076] A GPS receiver module consists of an antenna, an LNA, and a controller, etc. Figure 6 As shown, after the GPS antenna receives the synchronization signal from the satellite, it is preprocessed by the LNA amplifier and then enters the GPS receiver module to obtain the required latitude and longitude information and PPS second pulse signal for use by the control system.

[0077] like Figure 7 As shown, the wireless transceiver module enables wireless connection between the wireless terminal and the host computer, allowing all operations to be performed via the wireless terminal, avoiding the inconvenience of operating through the host computer. Measurement data is displayed in real-time via the wireless terminal and can be generated into graphs with a single click.

[0078] like Figure 8 As shown, the display module displays the main status of the host, such as battery voltage, transmission voltage, transmission current, GPS status information, alarm information, etc.

[0079] like Figure 9 As shown, the status monitoring module enables real-time monitoring of key components of the entire instrument, including but not limited to the functions shown in the above images. This system aims to improve the overall integrity of the system and make the product easier to maintain. The off-time detection circuit and constant voltage clamping circuit are integrated into this module, enabling the transmitter's functions and basic parameter measurements.

[0080] like Figure 10 As shown, the real-time processing system consists of an FPGA and a CPU. The current in the transmitting coil is sampled by a current sensor, resulting in a voltage signal proportional to the current. After appropriate filtering and amplification circuitry, this signal enters the high-speed ADC, where it is further processed by the FPGA to obtain a complete current sample. The system includes an Ethernet port for easy application expansion and a reserved SD card for convenient dual data backup, ensuring data integrity.

[0081] Furthermore, the receiving subsystem includes a signal processing module, a GPS positioning module, and a control and measurement module;

[0082] The signal processing module is used to process the electromagnetic signal generated by the receiving coil to obtain the processed electromagnetic signal.

[0083] The GPS positioning module is used to perform secondary measurement positioning based on the acquired latitude and longitude information and PPS second pulse signal;

[0084] The control and measurement module is used to control the terminal equipment and parameter settings, and to perform tests and system measurements after confirming that the GPS signal is valid.

[0085] Specifically, such as Figure 11 As shown, driven by the PPS second pulse, the transmitting and receiving systems achieve strict synchronization. After the receiving coil receives the eddy current field signal from the object under test, it is amplified and filtered and then enters the digital processing unit in the control system for signal processing, completing the subsequent digital processing and storage.

[0086] Furthermore, such as Figure 12 As shown, the signal processing module includes a signal preprocessing unit, a signal amplification and filtering unit, and an ADC unit;

[0087] The signal preprocessing unit is used to preprocess the electromagnetic signal generated by the receiving coil to obtain the preprocessed electromagnetic signal.

[0088] The signal amplification and filtering unit is used to amplify and filter the preprocessed electromagnetic signal to obtain the filtered electromagnetic signal.

[0089] The ADC unit is used to digitally process the filtered electromagnetic signal to obtain a digital signal.

[0090] like Figure 13 As shown, the GPS positioning system provides the PPS second pulse and latitude and longitude information required by the control system to realize the time synchronization of measurement and location information recording functions, which facilitates accurate positioning of secondary measurements for abnormal points.

[0091] like Figure 14 As shown, the control and measurement module: After the control system is initialized, it starts and performs a self-test. If the self-test fails or is not completed, it returns to the start process to perform a retest. When the system self-test is completed, it attempts to connect the terminal device. If the connection times out, it proves that the device is not connected properly and it is necessary to wait for the terminal device again. When the terminal device is successfully connected, the measurement parameters can be set, and the validity of the GPS signal can be determined. When the GPS signal is detected, the terminal device performs a self-test and selects appropriate parameters based on the test results, and finally starts the system measurement.

[0092] Furthermore, the data processing subsystem includes a curve normalization unit, a three-dimensional data measurement unit, and a data imaging unit;

[0093] The curve normalization unit is used to collect data to obtain attenuation curves of channels 1-12, and normalize the attenuation curves according to the distribution of the primary field to obtain attenuation curve profiles of channels 1-12.

[0094] The three-dimensional data measurement unit is used to run the vehicle system, continuously measure and sample, and obtain three-dimensional measurement data by measuring the distance between measurement points along the vehicle's direction of travel.

[0095] The data imaging unit is used to image the attenuation curve shape and resistivity of the data to determine a three-dimensional image of the underground target.

[0096] Specifically, the collected data yields attenuation curves of channels 1-12. These curves are then normalized based on the primary field distribution to obtain attenuation curve profiles of channels 1-12. The vehicle-mounted system operates at speeds of 3-10 km / h, completing one sampling cycle per second during continuous measurement. The spacing between measurement points along the vehicle's direction of travel is 0.8-2.7 meters, resulting in a 12×n three-dimensional dataset during continuous measurement. The attenuation curve morphology and resistivity of the data are then imaged to determine a three-dimensional image of the underground target.

[0097] This invention employs a small-coil transmitting and receiving detection technology, forming a three-dimensional single-transmitter, multi-receiver system with a single coil transmitting and multiple coils receiving. By improving upon the conventional two-dimensional single-transmitter, single-receiver detection method and developing single-transmitter, multi-receiver detection technology, it solves the problem that conventional detection systems can only achieve two-dimensional detection and cannot identify three-dimensional underground targets. Single-transmitter, multi-receiver transient electromagnetic measurement can also form a two-dimensional cross-section and advance along the measurement direction to complete three-dimensional underground measurement. Especially for linear underground targets, which appear as point features in conventional two-dimensional detection but as linear features in three-dimensional detection, the underground target is easier to identify on the three-dimensional inversion image. Therefore, this invention can more clearly identify underground pipelines and potential geological hazards. Furthermore, due to the short data acquisition time of this invention, a measurement speed of 3-10 km / h can still be achieved even with 10-64 superpositions, making it possible for rapid and large-scale detection in fields such as underground pipeline measurement, geological hazard detection, and soil exploration.

[0098] This invention is achieved through the following technical solutions: First, a framework for a small-coil three-dimensional transient electromagnetic measurement system is constructed. In urban environments and regional detection, transient electromagnetic detection is conducted using a vehicle-mounted method. The transient electromagnetic system is located at the rear of the vehicle and includes a 1.6m × 2m multi-turn rectangular transmitting coil. Sixteen receiving coils are located on the outer side of the short side of the transmitting coil. The receiving coils are multi-turn coils with a diameter of 5cm, spaced 5cm apart, and 0.5-0.8m away from one side of the transmitting coil. The transmitting and receiving coils are located in the same plane, 10-20cm above the ground, and supported by a non-metallic frame. Second, the measurement and control system includes a GPS receiving system, which controls the transmission and measurement, as well as the measurement positioning. Third, the transmitting system transmits a rectangular square wave with a current between 10-30A. The measurement system begins measurement after the transmission is powered off, with a measurement duration of 10ms. Fourth, based on multi-channel reception, the characteristics of the primary field are used for normalization, followed by resistivity inversion or imaging to form a three-dimensional underground resistivity distribution map along the measurement direction.

[0099] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A three-dimensional transient electromagnetic measurement system, characterized in that, include: The system comprises a transmitting subsystem, a receiving subsystem, and a data processing subsystem, all integrated into the vehicle platform. The transmitting subsystem is used to transmit transient electromagnetic signals generated by the transmitting coil to each receiving coil; The receiving subsystem is used to receive electromagnetic signals generated by each receiving coil; The receiving subsystem includes a signal processing module, a GPS positioning module, and a control and measurement module; The signal processing module is used to process the electromagnetic signal generated by the receiving coil to obtain the processed electromagnetic signal. The GPS positioning module is used to perform secondary measurement positioning based on the acquired latitude and longitude information and PPS second pulse signal; The control and measurement module is used to control the terminal equipment and parameter settings, and to perform tests and system measurements after confirming that the GPS signal is valid. The signal processing module includes a signal preprocessing unit, a signal amplification and filtering unit, and an ADC unit; The signal preprocessing unit is used to preprocess the electromagnetic signal generated by the receiving coil to obtain the preprocessed electromagnetic signal. The signal amplification and filtering unit is used to amplify and filter the preprocessed electromagnetic signal to obtain the filtered electromagnetic signal. The ADC unit is used to digitally process the filtered electromagnetic signal to obtain a digital signal. The data processing subsystem is used to process the received electromagnetic signals to obtain the underground three-dimensional electrical structure. The data processing subsystem includes a curve normalization unit, a three-dimensional data measurement unit, and a data imaging unit; The curve normalization unit is used to collect data to obtain attenuation curves of channels 1-12, and normalize the attenuation curves according to the distribution of the primary field to obtain attenuation curve profiles of channels 1-12. The three-dimensional data measurement unit is used to run the vehicle system, continuously measure and sample, and obtain three-dimensional measurement data by measuring the distance between measurement points along the vehicle's direction of travel. The data imaging unit is used to image the attenuation curve shape and resistivity of the data to determine the three-dimensional image of the underground target. The transmitting subsystem includes a power module, a GPS receiving module, a wireless transceiver module, a display module, a status monitoring module, and a control module; The power module is used to power itself and the transmitting and receiving coils; The GPS receiving module is used to receive satellite synchronization signals, process them, and obtain the latitude and longitude information and PPS second pulse signal of the target area. The wireless transceiver module is used for wireless communication between the control module and the host. The display module is used to connect to the control module and display the status of the host; The status monitoring module is used to detect the status of the overall system; The control module is used to sample the current of the transmitting coil through a current sensor to obtain a voltage signal that is proportional to the current. After passing through the corresponding filtering and amplification circuits, the signal enters the high-speed ADC and is processed by the FPGA to obtain the current sample. The power module includes a low-voltage unit and a high-voltage unit; The low-voltage unit is used for the instrument's own power supply loop. The energy comes from the internal 12V lithium battery or the external 12V lithium battery. After passing through the selector, it enters the DC-DC conversion circuit in the power controller to obtain the different operating voltages required by the instrument. The high-voltage unit is used as an energy loop to supply power to the coil. The energy comes from the external power supply input port of the transmitting coil. After passing through the overcurrent protection circuit and the overvoltage protection circuit, it enters the H-bridge. The H-bridge drive module provides the IGBT drive waveform to drive the H-bridge and transmits it out through the transmitting coil. The GPS receiving module includes a GPS antenna, an LNA amplifier, and a controller. After receiving the synchronization signal from the satellite, the GPS antenna is preprocessed by the LNA amplifier to obtain the required latitude and longitude information and PPS second pulse signal. The wireless transceiver module includes an antenna and an LNA amplifier, wherein the antenna is bidirectionally connected to the LNA amplifier, the LNA amplifier is bidirectionally connected to the wireless transceiver module, and the wireless transceiver module is bidirectionally connected to the control module. The detection is carried out on a vehicle. The transient electromagnetic system is located at the rear of the vehicle and includes a multi-turn rectangular transmitting coil. There are 16 receiving coils on the outside of the short side of the transmitting coil. The transmitting and receiving coils are located in the same plane. The transmitting system transmits rectangular square waves. The measurement system starts measuring after the transmission is powered off. Based on the multi-channel reception, the characteristics of the primary field are used for normalization. Then, resistivity inversion or imaging is performed to form a three-dimensional underground resistivity distribution map along the measurement direction.

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