Air-ground cooperative excitation integrated time-frequency receiving aviation electromagnetic detection system and method

Abstract

The invention discloses an air-ground cooperative excitation integrated time-frequency receiving aviation electromagnetic detection system and method, and belongs to the technical field of aviation geophysical detection. The electromagnetic detection system comprises a time frequency receiver, a helicopter aviation time domain transmitter, a time frequency receiving coil and a ground frequency domain transmitter. According to the electromagnetic detection method, time-domain pulses are transmitted in the air through the helicopter, frequency-domain continuous waves are transmitted on the ground, the time-domain pulses and the frequency-domain continuous waves are excited synchronously and received in a full-aviation mode, and helicopter aviation time-domain electromagnetic data and ground-air frequency-domain electromagnetic data are obtained through one-time flight based on the frequency point splitting and data decoupling technology. The electromagnetic detection system integrates the high-resolution imaging capability of helicopter aviation time domain electromagnetism to a hectometer-level shallow part and the strong penetration characteristic of ground-air frequency domain electromagnetism to a deep part, and is particularly suitable for large-range resource exploration under complex surface conditions such as mountainous areas and water areas; the method can realize shallow geologic structure refining considering large-depth geologic structure detection.

Description

Technical Field

[0001] The present invention relates to the technical field of airborne geophysical exploration, and specifically to an air-ground collaborative excitation integrated time-frequency receiving airborne electromagnetic detection system and method. This transient electromagnetic detection system emits time-domain pulses through a helicopter airborne electromagnetic emission system and emits 2 n pseudo-random continuous waves through a ground frequency-domain emission system, and the two are simultaneously excited and the entire airborne electromagnetic is received, which can achieve the refinement of shallow geological structures while taking into account the detection of large-depth geological structures. Background Technique

[0002] The detection depth of the traditional all-airborne helicopter airborne time-domain electromagnetic system is only in the hundreds of meters level but has high resolution. The detection depth of the semi-airborne frequency-domain or time-domain electromagnetic detection with ground emission and airborne reception is deeper but the overall resolution is poor. Therefore, the all-airborne helicopter airborne time-domain electromagnetic system and the semi-airborne frequency-domain or time-domain electromagnetic detection system are integrated to conduct electromagnetic detection on the same survey area, so as to achieve the refinement of shallow stratum data while maintaining a large detection depth range. If the two electromagnetic detection systems work simultaneously, for the received electromagnetic signals, they are mutual interference sources, making it difficult to separate the electromagnetic signals from each other. Therefore, most of the existing combined schemes of helicopter airborne electromagnetic method and ground-air electromagnetic method are time-sharing excitation, and separate flight detections are required for the data of each system, with low efficiency and poor spatio-temporal matching of data. The following are some documents of the prior art.

[0003] CN202210596682.1 discloses a mixed-field source electromagnetic detection system, which needs to carry two types of coils, namely an airborne highly sensitive small-bandwidth coil and an airborne low-sensitive large-bandwidth coil respectively. Since it cannot achieve one-time flight detection and simultaneously receive ground electrical source and airborne magnetic source data, its detection cost and detection efficiency have not been optimized.

[0004] CN201711067239.0 discloses an airborne mixed-field source coded electromagnetic detection system, whose helicopter platform simultaneously carries high-frequency transmitting and receiving antennas, and low-frequency transmitting and receiving antennas. The time-domain and frequency-domain combined transmission is realized on the helicopter platform. The time-domain transient electromagnetic detection system detects deep geological bodies, and the low-frequency pseudo-random emission system is responsible for shallow geological bodies. However, due to the limitation of helicopter power supply for the excitation source, its detection depth is still in the hundreds of meters level, depending on the helicopter airborne time-domain electromagnetic system with load.

[0005] CN200810050865.3 discloses a combined field source emission device for the mixed-field source electromagnetic method, whose goal is to emit field source signals that can switch electrical sources and magnetic sources in a set of equipment. It is designed for ground emission sources and cannot be integrated into the helicopter airborne electromagnetic detection system due to the power limitation of the helicopter.

[0006] CN200810143301.4 discloses a combined field source artificial source frequency domain electromagnetic sounding method, which is a combination of low / mid / high frequency transmitters and low / mid / high frequency receivers. By means of a combined current excitation signal composed of different main frequencies and different powers, the geoelectric response information of all frequencies in different frequency groups is received simultaneously at one time. However, this method is a frequency domain ground electromagnetic detection method and cannot achieve rapid geological detection in complex terrain areas. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides an air-ground collaborative excitation integrated time-frequency receiving airborne electromagnetic detection system and method. By means of the full reception of the ground frequency domain electromagnetic electrical source response and the airborne time domain electromagnetic magnetic source response, the frequency point separation and the electromagnetic response decoupling method, one flight can take into account the shallow high-resolution of the helicopter time domain electromagnetic method and the large-depth detection of the air-ground frequency domain electromagnetic method. Based on the flexible helicopter platform, the present invention combines the shallow high-resolution advantage of the helicopter airborne time domain electromagnetic detection and the large-depth advantage of the helicopter air-ground frequency domain electromagnetic detection, and realizes the all-round electromagnetic exploration with extremely high efficiency, rapidity, large range and adaptability to harsh geological conditions.

[0008] In order to achieve the above object, the solution provided by the present invention is as follows: An air-ground collaborative excitation integrated time-frequency receiving airborne electromagnetic detection system, comprising a helicopter mounting device and a ground device. Among them, the helicopter mounting device includes in-cabin equipment and a suspended device suspended below the helicopter by a suspension rope. The suspended device is electrically connected to the in-cabin equipment through a cable; The suspended device includes: A helicopter airborne time domain electromagnetic transmitting coil; A helicopter airborne time domain electromagnetic compensation coil electrically connected to the helicopter airborne time domain transmitting coil; An attitude sensor installed on the helicopter airborne time domain electromagnetic transmitting coil; A time-frequency receiving coil fixed on a horizontal cross-tension rope; A preamplifier fixed on the suspension rope and electrically connected to the time-frequency receiving coil; The in-cabin equipment includes: A helicopter airborne time domain transmitter electrically connected to the helicopter airborne time domain electromagnetic transmitting coil, which is used to generate a bipolar pulse current in the helicopter airborne time domain electromagnetic transmitting coil as a magnetic source; A time-frequency receiver, which is used to collect the induced voltage signal amplified by the preamplifier from the time-frequency receiving coil and other auxiliary information; A radar altimeter, which is used to obtain the helicopter height above the ground information and transmit the height above the ground information to the time-frequency receiver; A GPS device is used to obtain the GPS information of a helicopter and transmit the GPS information to a time-frequency receiver; The ground device includes: Two grounding electrodes inserted into the ground; A ground frequency-domain transmitter electrically connected to the grounding electrodes, which is used to generate 2 n pseudo-random continuous wave currents in the two grounding electrodes; the ground frequency-domain transmitter and the two grounding electrodes are located on the same straight line; A ground station is used to obtain the three-component magnetic field data of the natural field. The ground station includes a three-component receiving sensor and a supporting acquisition device; Among them, the helicopter airborne time-domain transmitter and the ground frequency-domain transmitter are excited simultaneously, and the time-domain electromagnetic excitation fundamental frequency of the helicopter airborne time-domain transmitter and its odd harmonics, and the 2 n minimum frequency difference between the two sets of frequency points of all excitation frequency points of the pseudo-random of the ground frequency-domain transmitter is greater than 0.

[0009] As a specific implementation manner of the present invention, the X and Y components in the three-component sensor in the ground station are respectively parallel to the geomagnetic north-south direction and the east-west direction, and the Z component is completely perpendicular to the geoid.

[0010] As a specific implementation manner of the present invention, the relative height difference between the equipment in the cabin and the suspended equipment is 30 meters to 50 meters.

[0011] An air-ground collaborative excitation integrated time-frequency receiving airborne electromagnetic detection method includes the following steps: S1. Arrange the ground frequency-domain transmitter, the grounding electrodes and the ground station according to the location of the survey area, and set the survey line; determine the time-domain electromagnetic excitation fundamental frequency of the helicopter airborne time-domain transmitter f 0 and the 2 n pseudo-random excitation fundamental frequency of the ground frequency-domain transmitter f 1 ; Determine the time-domain electromagnetic excitation fundamental frequency f 0 and the 2 n pseudo-random excitation fundamental frequency f 1 rules are as follows: Taking the maximum of the minimum frequency difference between the time-domain electromagnetic excitation fundamental frequency and its odd harmonics, and all excitation frequency points of the 2 n pseudo-random as the optimization objective, determine each excitation fundamental frequency, and its objective function is the following formula: ; ; N0 Indicates the order of the harmonic wave excited by time-domain electromagnetic excitation; n Indicates 2 n Pseudo-random order; Or, taking the minimum frequency difference between two sets of frequency points, namely the odd and even harmonics of the fundamental frequency of time-domain electromagnetic excitation and 2 n Pseudo-random all excitation frequency points, as the optimization objective, to determine each excitation fundamental frequency, and its objective function is as follows: ; ; When solving the above objective function, it is found that under the above two conditions, the two excitation fundamental frequencies and the maximized minimum frequency difference respectively satisfy specific relationships. Therefore, the specific relationships can be used to determine each excitation fundamental frequency, thereby reducing the calculation amount. Therefore, as a specific embodiment of the present invention, Taking the minimum frequency difference between two sets of frequency points, namely the fundamental frequency of time-domain electromagnetic excitation and its odd harmonics, and 2 n Pseudo-random all excitation frequency points, as the optimization objective to determine each excitation fundamental frequency, the two excitation fundamental frequencies satisfy the following relationship: ; In the formula, m Is any non-negative integer. At this time, the obtained maximized minimum frequency difference is: ; Taking the minimum frequency difference between two sets of frequency points, namely the odd and even harmonics of the fundamental frequency of time-domain electromagnetic excitation and 2 n Pseudo-random all excitation frequency points, as the optimization objective to determine each excitation fundamental frequency, the two excitation fundamental frequencies satisfy the following relationship: ; At this time, the obtained maximized minimum frequency difference is: ; In this step, the waveform of the helicopter airborne time-domain transmitter can select a suitable bipolar triangular wave or bipolar trapezoidal wave pulse according to relevant geological data information; when arranging the grounding electrodes, the distance between the poles and the geographical location are determined according to the survey area range to ensure that the outermost end of the survey area is within the action range of the frequency-domain excitation field; the ground station should be set near the survey area and away from human interference; the survey line should be designed with horizontal equal intervals in the survey area according to the detection resolution, and reciprocating lines are set in key areas.

[0012] S2. Start the equipment, including turning on the hoisting equipment using the ground power supply; This step includes starting the ground station and collecting the three-component magnetic field data of the natural field; according to the determined 2 n Pseudo-random excitation frequencyf 1 Start the ground frequency-domain transmitter; when using the ground power supply, turn on the time-frequency receiver and the radar altimeter, and the GPS device (including its auxiliary system), and according to the determined fundamental frequency of electromagnetic excitation in the time domain f 0 Start the helicopter airborne time-domain transmitter in conjunction with the waveform, and turn on the attitude sensor located on the helicopter airborne time-domain electromagnetic emission coil; disconnect the ground power supply after connecting the helicopter power supply; S3. The helicopter flies along the survey line under the condition of keeping the height of the suspended equipment 30 m to 200 m above the ground. During the flight, the helicopter airborne time-domain transmitter and the ground frequency-domain transmitter are excited simultaneously. The time-frequency receiver collects electromagnetic data, the radar altimeter obtains the helicopter's height information above the ground, and the GPS device obtains the helicopter's GPS information. Moreover, the height information above the ground and the GPS information are bound to the electromagnetic data through time stamps; In this step, the electromagnetic data collected by the time-frequency receiver is the time-domain magnetic source electromagnetic response signal excited in the air and the frequency-domain electric source electromagnetic response signal excited on the ground, which are induced by the time-frequency receiving coil and pre-amplified by a low-noise pre-amplifier.

[0013] S4. After the flight, collect the data of the time-frequency receiver, the attitude sensor and the ground station, and split the collected data according to the survey line, and align the electromagnetic data with the geographical location; S5. Data processing: Based on the fundamental frequency of electromagnetic excitation in the time domain and its odd harmonic frequencies and 2 n pseudo-random excitation frequency points, the electromagnetic data processed in step S4 is processed by equal-amplitude comb filtering or other filters and then decimated to obtain the helicopter airborne time-domain electromagnetic decimated data, and the ground-air frequency-domain frequency point data is obtained by fast Fourier transform or quadrature phase-locking, completing data decoupling; S6. Inversion imaging: According to the ground-air frequency-domain electromagnetic inversion imaging method, calculate the apparent resistivity of the exploration area ρ 频 by calculating the apparent resistivity of the ground-air frequency-domain frequency point data and the ground station signal; according to the helicopter airborne electromagnetic inversion imaging method, calculate the resistivity of the exploration area ρ 时 .

[0014] Beneficial effects: The present invention first proposes an airborne electromagnetic detection system of "simultaneously exciting helicopter airborne time-domain pulse and ground-air frequency-domain continuous wave, and integrally receiving time-frequency signals in the air by helicopter", and proposes a time-frequency signal decoupling method supporting the airborne electromagnetic detection system. By separately setting the frequency points of time-frequency excitation and screening the frequencies of electromagnetic data, the data aliasing problem in simultaneous integrated reception is solved. Generally speaking, based on the high mobility of the helicopter platform, the present invention constructs a set of electromagnetic exploration systems with full terrain coverage and high efficiency by integrating the high-resolution imaging ability of airborne time-domain electromagnetic for shallow subsurface within hundreds of meters and the strong penetration characteristics of ground-air frequency-domain electromagnetic for deep subsurface. It is particularly suitable for large-scale resource exploration under complex surface conditions such as mountainous areas and water areas. Compared with the electromagnetic time-frequency excitation methods adopted by other ground sources, it can achieve the effect of refined shallow detection while taking into account large detection depths. Compared with separately conducting flight detections for ground-air frequency-domain electromagnetic and airborne time-domain electromagnetic, it has low detection costs and high detection efficiency. Brief Description of the Drawings

[0015] Figure 1 is a schematic diagram of the airborne electromagnetic detection system with integrated time-frequency reception for airborne-ground collaborative excitation of the present invention; Figure 2 is a schematic diagram of the frequency point data of the 8.4 Hz fundamental frequency, 7th order, 2 n pseudo-random frequency-domain electromagnetic after data decoupling in Example 2; Figure 3 is a schematic diagram of the trace data of the 25 Hz fundamental frequency time-domain electromagnetic after data decoupling in Example 2; Figure 4 is a schematic diagram of the frequency point data of the 7.5 Hz fundamental frequency, 7th order, 2 n pseudo-random frequency-domain electromagnetic after data decoupling in Example 3; Figure 5 is a schematic diagram of the trace data of the 75 Hz fundamental frequency time-domain electromagnetic after data decoupling in Example 3; In the figure, helicopter 1; time-frequency receiver 2; radar altimeter 3; GPS device 4; helicopter airborne time-domain transmitter 5; time-frequency receiving coil 6; helicopter airborne time-domain electromagnetic transmitting coil 7; helicopter airborne time-domain compensation coil 8; preamplifier 9; attitude sensor 10; ground frequency-domain transmitter 11; grounding electrode 12; ground station 13. Detailed Embodiments

[0016] The following further elaborates on the present invention in detail in conjunction with embodiments and the accompanying drawings, but the implementation manners of the present invention are not limited thereto.

[0017] Example 1: Please refer to Figure 1, which shows a schematic diagram of a specific structure of the integrated airborne and ground collaborative excitation time-frequency receiving airborne electromagnetic detection system of the present invention. The integrated airborne and ground collaborative excitation time-frequency receiving airborne electromagnetic detection system of the present invention includes a helicopter mounting device and a ground device. Among them, the ground device is arranged on the ground, and the helicopter mounting device flies with helicopter 1. The helicopter mounting device further includes in-cabin equipment and suspended equipment. The suspended equipment is structurally connected to helicopter 1 through a suspension rope and electrically connected through a cable, and the relative height between the two is 30 meters to 50 meters.

[0018] The suspended equipment includes a helicopter airborne time-domain electromagnetic transmitting coil 7, a helicopter airborne time-domain electromagnetic compensation coil 8, an attitude sensor 10, a time-frequency receiving coil 6, and a preamplifier 9. Among them, the helicopter airborne time-domain electromagnetic compensation coil 8 is electrically connected to the helicopter airborne time-domain electromagnetic transmitting coil 7; the attitude sensor 10 is installed on the helicopter airborne time-domain electromagnetic transmitting coil 7; the time-frequency receiving coil 6 is a flexible time-frequency receiving coil and is fixed on a horizontal cross-tension rope; the preamplifier 9 uses a low-noise preamplifier and is fixed on the suspension rope and electrically connected to the time-frequency receiving coil 6.

[0019] The in-cabin equipment includes a helicopter airborne time-domain transmitter 5, a time-frequency receiver 2, a radar altimeter 3, and a GPS device 4. Among them, the helicopter airborne time-domain transmitter 5 is electrically connected to the helicopter airborne time-domain electromagnetic transmitting coil 7 and is used to generate a bipolar pulse current in the helicopter airborne time-domain electromagnetic transmitting coil 7; the time-frequency receiver 2 is used to collect the induced voltage signal amplified by the preamplifier 9 from the time-frequency receiving coil 6 and other auxiliary information; the radar altimeter 3 is used to obtain the height information of helicopter 1 from the ground and transmit this information to the time-frequency receiver 2; the GPS device 4 is used to obtain the GPS information of helicopter 1 and transmit this information to the time-frequency receiver 2.

[0020] The ground device includes a ground frequency-domain transmitter 11, two grounding electrodes 12, and a ground station 13. Among them, the two grounding electrodes 12 are connected to both ends of a cable and inserted into the soil. The cable is electrically connected to the ground frequency-domain transmitter 11, and the two grounding electrodes 12 and the cable are on a straight line. The ground frequency-domain transmitter is used to generate 2 n pseudo-random continuous wave current in the two grounding electrodes; the ground station 13 includes a three-component receiving sensor and a supporting acquisition device, which is used to obtain the three-component magnetic field data of the natural field. The X and Y components in the three-component sensor are parallel to the geomagnetic north-south direction and the east-west direction respectively, and the Z component is completely perpendicular to the geoid. The helicopter airborne time-domain transmitter 5 in the air and the ground frequency-domain transmitter 11 are excited simultaneously, and the time-domain electromagnetic excitation fundamental frequency of the helicopter airborne time-domain transmitter and its odd harmonics, and the 2 n pseudo-random all excitation frequency points of the ground frequency-domain transmitter. The minimum frequency difference between these two groups of frequency points is greater than 0.

[0021] Embodiment 2: An airborne-ground collaborative excitation integrated time-frequency receiving airborne electromagnetic detection method, comprising the following steps: S1. Arrange a ground frequency-domain transmitter, a grounding electrode, and a ground station according to the location of the survey area, and set survey lines; determine the time-domain electromagnetic excitation fundamental frequency of the helicopter airborne time-domain transmitter f 0 and the 2 n pseudo-random excitation fundamental frequency of the ground frequency-domain transmitter f 1 ; Specifically, after selecting the time-domain electromagnetic excitation fundamental frequency of 25 Hz and the excitation fundamental frequency of the 2 n pseudo-random sequence to be in the range of 5 Hz to 10 Hz and its order to be 7, with the goal of maximizing the minimum frequency difference between the time-domain electromagnetic excitation fundamental frequency and its odd harmonics, and all the excitation frequency points of the 2 n pseudo-random sequence (step size: 0.1 Hz), select the fundamental frequency of the 2 n pseudo-random sequence to be 8.4 Hz. According to the geological data information, set the time-domain electromagnetic excitation triangular current waveform, with the excitation current peak value of 500 A. Arrange 30 mutually parallel horizontal survey lines at an interval of 100 m. The two grounding electrode points are located at the edge of the exploration area, with a straight-line distance of 3 km, and the ground frequency-domain transmitter is placed in the middle position between the two grounding poles. The ground station is arranged 2 km northeast of the survey area, far away from high-voltage wires and factories, and calibrate the three-component sensor. The X / Y components are aligned with the geomagnetic north-south / east-west directions respectively, and the verticality error of the Z component is < 0.5°; S2. Start the equipment, including starting the ground station, and collecting the three-component magnetic field data of the natural field; start the ground frequency-domain transmitter according to the determined 2 n pseudo-random excitation frequency f 1 ; use the ground power supply to turn on the time-frequency receiver and the radar altimeter, the GPS device (including its auxiliary system), and start the time-domain transmitter according to the determined time-domain electromagnetic excitation fundamental frequency f 0 and the waveform; turn on the attitude sensor on the helicopter airborne time-domain electromagnetic emission coil; S3. The helicopter flies along the survey line under the condition of keeping the height of the suspended equipment 30 m to 150 m above the ground. During the flight, the helicopter airborne time-domain transmitter and the ground frequency-domain transmitter are simultaneously excited. The time-frequency receiver collects electromagnetic data (including the helicopter airborne time-domain electromagnetic response signal and the ground-air frequency-domain electromagnetic response signal) at a sampling rate of 192 kHz. The radar altimeter obtains the helicopter's height information above the ground, and the GPS device obtains the helicopter's GPS information, and the height information above the ground and the GPS information are bound to the electromagnetic data through time stamps; S4. After the flight, turn off the helicopter airborne time-domain transmitter and the ground frequency-domain transmitter; enable the ground power supply to take out the data in the time-frequency receiver, take out the attitude sensor data, and save the three-component magnetic field data of the ground station to end the ground station acquisition work. Intercept the collected data according to the survey line, GPS data points and the planned survey line position coordinate points, and align the electromagnetic data with the geographical location through the time stamp and GPS information; S5. Data processing: Based on the fundamental frequency of the time-domain electromagnetic excitation and its odd harmonic frequencies and 2 n pseudo-random excitation frequency points, the electromagnetic data processed in step S4 is subjected to equal-amplitude comb filtering and then decimated to obtain the helicopter airborne time-domain electromagnetic decimated data, and the ground-air frequency-domain frequency point data is obtained through fast Fourier transform to complete the decoupling of the electromagnetic data. The decoupled ground-air frequency-domain frequency point data is as Figure 2 shown. Its frequency point curves are smooth, the relationship between frequency points is clear, and the response amplitude levels are close; the decoupled helicopter airborne time-domain electromagnetic decimated data is as Figure 3 shown. Each time trace curve is smooth, the relationship between traces is significant, and there is no overlap of curves between traces; S6. Inversion imaging: According to the ground-air frequency-domain electromagnetic inversion imaging method, calculate the apparent resistivity of the ground-air frequency-domain frequency point data and the ground station signal to obtain the apparent resistivity information ρ 频 of the exploration area; according to the helicopter airborne electromagnetic inversion imaging method, calculate the resistivity of the helicopter airborne time-domain electromagnetic decimated data to obtain the resistivity information ρ 时 of the exploration area; S7. Data interpretation: Combine the constructed metallogenic geological model with the inversion imaging to delineate the electromagnetic anomaly area, and combine geological data such as strata, structures, and geochemical analysis in the anomaly area to optimize the target area and achieve effective exploration of mineral resources.

[0022] Example 3: The steps are the same as those in Example 2, except that some parameters are different. The specific differences are as follows: In step S1, after selecting the fundamental frequency of the time-domain electromagnetic excitation as 75 Hz and 2 n the fundamental frequency of the pseudo-random sequence is between 5 Hz and 10 Hz and its order is 7, taking the minimum frequency difference between the odd and even harmonics of the fundamental frequency of the time-domain electromagnetic excitation and 2 n all the excitation frequency points of the pseudo-random as the optimization target (the step size is 0.5 Hz), select 2 nThe fundamental frequency of the pseudo-random sequence is 7.5 Hz. According to the geological data information, a trapezoidal current waveform for electromagnetic excitation in the time domain is set, and the peak value of the excitation current is 400 A. 50 mutually parallel horizontal survey lines are arranged at intervals of 100 m. The two electrode points are located at the edge of the exploration area, with a straight-line distance of 5 km, and the ground frequency-domain transmitter is placed at the middle position between the two pole points. The ground station is arranged 1.5 km northeast of the survey area. It is far away from high-voltage wires and factory buildings. The calibration three-component sensors X / Y are aligned with the geomagnetic north-south / east-west directions respectively, and the verticality error of the Z component is < 0.5°.

[0023] In step S3, the helicopter flies along the survey line while keeping the height of the suspended equipment 30 m to 100 m above the ground.

[0024] In step S5, the decoupled ground-air frequency-domain electromagnetic data at each frequency point are as Figure 4 shown. The curves at each frequency point are smooth, and the relationships between frequency points are clear; the decoupled helicopter airborne time-domain electromagnetic trace data are as Figure 5 shown. The curves of each time trace are smooth, and the relationships between traces are significant.

[0025] The above is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be covered within the protection scope of the present invention.

Claims

1. An air-ground coordinated excitation integrated time-frequency receiving airborne electromagnetic detection system, characterized in that: It includes a helicopter mounting device and a ground device, wherein the helicopter mounting device includes equipment in the cabin and a hanging device hung under the helicopter via a hanging rope, and the hanging device is electrically connected to the equipment in the cabin via a cable; The hoisting equipment comprises: Helicopter aviation time domain electromagnetic transmitting coil; A helicopter aviation time domain electromagnetic compensation coil electrically connected to the helicopter aviation time domain electromagnetic transmitting coil; An attitude sensor mounted on the helicopter's aviation time-domain electromagnetic transmitting coil; A time and frequency receiving coil fixed on the horizontal cross rope; a preamplifier fixed to the suspension rope and electrically connected to the time-frequency receiving coil; The cabin equipment includes: a helicopter aviation time domain transmitter electrically connected to the helicopter aviation time domain transmitting coil, for generating a bipolar pulse current in the helicopter aviation time domain transmitting coil; A time-frequency receiver, used to collect the induced voltage signal and other auxiliary information from the time-frequency receiving coil and amplified by the preamplifier; A radar altimeter, used to obtain the height information of the helicopter above the ground, and transmit the height information above the ground to the time-frequency receiver; A GPS device, used to obtain GPS information of the helicopter and transmit the GPS information to the time-frequency receiver; The ground device comprises: two grounding electrodes driven into the ground; A ground frequency domain transmitter electrically connected to the ground electrodes, for generating 2 n Pseudo-random continuous wave current; the ground frequency domain transmitter and the two ground electrodes are located on the same straight line; A ground station, used to obtain three-component magnetic field data of a natural field, the ground station comprising a three-component receiving sensor and a matching collection device; The helicopter aviation time domain transmitter and the ground frequency domain transmitter are excited simultaneously, and the time domain electromagnetic excitation fundamental frequency and its odd harmonics of the helicopter aviation time domain transmitter and the 2 n The minimum frequency difference between the two sets of frequency pairs of all pseudo-random excitation frequency points is greater than 0.

2. The air-ground coordinated excitation integrated time-frequency receiving airborne electromagnetic detection system according to claim 1 is characterized in that: The relative height difference between the equipment in the cabin and the suspended equipment is 30 meters to 50 meters.

3. The air-ground coordinated excitation integrated time-frequency receiving airborne electromagnetic detection system according to claim 1 is characterized in that: The X and Y components of the three-component sensor are parallel to the geomagnetic north-south direction and the east-west direction respectively, and the Z component is completely perpendicular to the geoid.

4. A method for air-ground coordinated excitation integrated time-frequency receiving airborne electromagnetic detection, using the air-ground coordinated excitation integrated time-frequency receiving airborne electromagnetic detection system according to any one of claims 1 to 3 for detection, characterized in that: The steps include: S1. Arrange the ground frequency domain transmitter, ground electrode and ground station according to the location of the survey area, and set the survey line; determine the time domain electromagnetic excitation fundamental frequency of the helicopter aviation time domain transmitter f 0 and 2 of the terrestrial frequency domain transmitter n Pseudo-random excitation fundamental frequency f 1; Determine the fundamental frequency of the time domain electromagnetic excitation f 0 and 2 n Pseudo-random excitation fundamental frequency f The rules for 1 are as follows: To maximize the fundamental frequency and its odd harmonics, 2 n The minimum frequency difference of the two sets of frequency points of all pseudo-random excitation frequency points is the optimization target to determine each excitation fundamental frequency; or, to maximize the odd and even harmonics of the time domain electromagnetic excitation fundamental frequency, 2 n The minimum frequency difference between these two frequency pairs of all pseudo-random excitation frequencies is the optimization target, and each excitation fundamental frequency is determined; S2, start the equipment, including starting the hoisting equipment using the ground power supply; S3, the helicopter flies along the survey line under the condition of keeping the height of the hanging equipment 30 meters to 200 meters above the ground. During the flight, the helicopter aviation time domain transmitter and the ground frequency domain transmitter are simultaneously excited, the time and frequency receiver collects electromagnetic data, the radar altimeter obtains the height information of the helicopter above the ground, and the GPS device obtains the GPS information of the helicopter, and the height information and the GPS information are bound to the electromagnetic data through a timestamp; S4, after the flight, collect data from the time-frequency receiver, the attitude sensor and the ground station, split the collected data according to the survey line, and align the electromagnetic data with the geographical location; S5, data processing: based on the fundamental frequency of electromagnetic excitation in the time domain and its odd harmonic frequencies and 2 n Pseudo-random excitation frequency points, the electromagnetic data processed in step S4 is processed by equal-amplitude comb filtering or other filters to obtain helicopter aviation time domain electromagnetic channel extraction data, and the ground-to-air frequency domain frequency point data is obtained by fast Fourier transform or orthogonal phase locking to complete data decoupling; S6. Inversion imaging: According to the ground-space frequency domain electromagnetic inversion imaging method, the ground-space frequency domain frequency point data and the ground station signal are used to calculate the apparent resistivity to obtain the apparent resistivity information ρ of the exploration area. 频 According to the helicopter airborne electromagnetic inversion imaging method, the helicopter airborne time domain electromagnetic extraction data is used for resistivity calculation to obtain the resistivity information of the exploration area ρ 时 .

5. The air-ground coordinated excitation integrated time-frequency receiving airborne electromagnetic detection method according to claim 4 is characterized in that: Determining the fundamental frequency of electromagnetic excitation in the time domain f 0 and 2 n Pseudo-random excitation fundamental frequency f The rule of 1 is simplified to: the fundamental frequency of electromagnetic excitation in the time domain f 0 and 2 n Pseudo-random excitation fundamental frequency f 1 satisfies the following relationship: or ; In the formula, m is any non-negative integer.

Images