Intelligent digital correlator based on GPS time correction

Abstract

The application discloses a kind of intelligent digital correlation instrument based on GPS time setting, with GPS global unified time as core timing reference, built-in positioning module and intelligent timing processing unit in equipment, satellite time signal can be received in real time, complete equipment local clock automatic calibration and dynamic error compensation, completely eliminate the cumulative error generated by local crystal oscillator.Simultaneously relying on standardization unified timing coordinate system, it provides high-precision timing support for multi-channel signal acquisition, data transmission, digital correlation operation, multi-device networking collaborative operation;Equipment carries adaptive time keeping algorithm, can cope with satellite obstruction, weak signal, short time lockout and other working conditions under timing stability problem, and cooperate with optimized signal filtering and error equalization mechanism, ensure that equipment continues high-precision stable operation under complex field environment.

Description

Technical Field

[0001] This invention relates to the field of municipal water supply network leakage technology, specifically to an intelligent digital correlator based on GPS time synchronization. Background Technology

[0002] Urban water supply networks are core infrastructure for ensuring urban livelihoods and utilizing water resources. During long-term service, these networks are prone to malfunctions such as pipe cracks and leaks at joints due to factors like pipe aging and soil corrosion. Therefore, accurate and efficient leak location technology is a core necessity for network operation and maintenance. Currently, the mainstream leak detection equipment in the industry is the acoustic digital correlator (DCR). Its core principle is to simultaneously collect leak turbulence noise signals from sensors at both ends of the pipe, and then calculate the leak location using the signal delay difference combined with sound velocity and pipe distance. Compared to traditional manual listening methods and zone measurement methods, the DCR has advantages in terms of high automation and wide positioning range, and has been widely used in pipeline leak detection. However, existing traditional DCRs still have many core technical deficiencies in actual complex operating conditions, making it difficult to meet the requirements for high-precision leak detection. Existing correlators generally employ analog audio signal wireless transmission systems. Examples include patent CN 114383785A and products from companies like Seba and Haomai Shuwei. Sound probes collect analog data and transmit it to a host computer for data processing and leak detection. However, analog data transmission is subject to varying degrees of interference. Two sets of similar devices operating close to each other can directly affect their normal operation. Furthermore, the software is often not updated for extended periods, resulting in low levels of intelligence. To address these shortcomings, this paper proposes a high-precision GPS-based intelligent digital correlator for leak detection. This system enables unified timing across multiple probes, boasts strong anti-interference capabilities, and a high degree of intelligence. By establishing an absolutely unified time reference through GPS satellite timing, it eliminates local clock drift errors, improves the accuracy of leak signal delay calculation and leak location, and adapts to leak detection needs in various complex pipeline network conditions. Summary of the Invention

[0003] In view of the problems existing in the prior art, the present invention discloses an intelligent digital correlator based on GPS time synchronization. The GPS global unified time is used as the core timing reference. The device has a built-in GPS or Beidou module and an intelligent timing processing unit, which can receive satellite timing signals in real time, complete the automatic calibration and dynamic error compensation of the device's local clock, and completely eliminate the cumulative error generated by the local crystal oscillator. Simultaneously, relying on a standardized and unified time-series coordinate system, it provides high-precision time-series support for multi-channel signal acquisition, data transmission, digital correlation calculation, and multi-device network collaborative operation. The equipment is equipped with an adaptive timekeeping algorithm, which can cope with time-series stability issues under conditions such as satellite obstruction, weak signals, and short-term loss of lock. Combined with an optimized signal filtering and error averaging mechanism, it ensures continuous high-precision and stable operation of the equipment in complex field environments. The technical solution adopted includes a receiver, a transmitter, and a transmitter module. The receiver consists of a main station system, a control system, a battery, a display and human-machine interaction module, a communication module one, a positioning module, a communication module two, a wireless module, and a wireless module antenna. The transmitter and transmitter have the same system structure, both consisting of a probe, a precision cable connector, an amplification and filtering module, an independent analog-to-digital conversion module, a controller, a transmitter positioning module, a transmitter GPS antenna, a transmitter wireless module, a transmitter wireless module antenna, and a transmitter battery module.

[0004] As a preferred embodiment of the present invention, the main station system is responsible for the coordinated operation of all modules, including wireless module data transmission and reception and control, intelligent timing calibration, data synchronization acquisition and control, digital correlation processing, and data storage. The control system contains a control MCU module that communicates with the main station system via UART and serves as the execution mechanism for the entire system. A built-in power control module manages the power supply of the system modules and connects to the positioning module via UART, handling the reception and initial filtering of GPS data from the host device. The battery outputs +12.6V, which, after passing through the control system, powers the display and human-machine interface module, communication module, positioning module, and wireless module. The display and human-machine interface module consists of a touchscreen, control board, and booster board. Operators set essential parameters such as pipe material, length, and diameter using the touchscreen module; the main station system then acquires and processes these parameters. The display and human-machine interaction module receives system control commands and forwards them to the main station system. Through the control system and wireless module, these commands are transmitted to the transmitter and receiver, completing the control command distribution. The display and human-machine interaction module is also responsible for displaying test results, showing probe data signal spectrum information and location information of leak points. Communication module one uses Wi-Fi or 4G to build a local area network (LAN) for the host system. The host system and wireless module are connected to the LAN via network cable, enabling network interconnection throughout the system. Simultaneously, communication module one provides an external network interface to the LAN, allowing handheld tablet devices to connect and enabling remote screen projection. In special circumstances, communication module one can upload system processing inputs to the cloud system via the 4G module. Communication module two is a high-gain antenna combining GPS, Wi-Fi, and 4G. The GPS antenna operates at 1561±10MHz, the Wi-Fi at 2400MHz-2500MHz, and the 4G at 700MHz-2700MHz. It ensures normal GPS signal reception and 4G signal transmission and reception, and can provide Wi-Fi signals for network formation. The wireless module is connected to the routing module interface of communication module one via a network cable. The main station system communicates with the transmitter's wireless module and the transmitter's wireless module via the network interface. The wireless module antenna is a 15dB high-gain antenna, operating in the 902-928MHz frequency band, with a center frequency of 915MHz.

[0005] As a preferred embodiment of the present invention, the transmitter and transmitter have the same structure, both consisting of a probe, a precision cable connector, an amplification and filtering module, an independent analog-to-digital converter module, a controller, a transmitter positioning module, a transmitter GPS antenna, a transmitter wireless module, a transmitter wireless module antenna, and a transmitter battery module. The difference between the transmitter and transmitter lies in the controller system code ID and the GPS location information.

[0006] As a preferred embodiment of the present invention, the probe incorporates a precision piezoelectric sensor and a low-noise preamplifier circuit to acquire the leakage acoustic signal and perform the first-stage signal amplification. An amplification and filtering module performs the second-stage amplification of the acoustic signal, ensuring sufficient amplitude and signal-to-noise ratio. The probe and the amplification and filtering module are connected via a precision cable connector, which has four-pin aviation connectors at both ends. The four pins are for power supply (VCC), ground (GND), signal (SIG), and control (CTL). The transmitter positioning module uses a GPS module, with the GPS output pulse per second (PPM) as a reference, providing a unified clock reference for synchronous data acquisition by the probe. This ensures that the transmitter's analog-to-digital conversion and analog-to-digital conversion are synchronized to a single time acquisition signal, thus ensuring synchronous data acquisition. The transmitter's GPS antenna is a small-sized GPS antenna operating in the 1561±10MHz frequency range. The transmitter's battery module outputs +12V. The transmitter's wireless module connects to the controller via an RJ45 Ethernet port. The controller transmits data to the receiver's wireless module via a network interface, and finally to the main control system for processing.

[0007] In a preferred embodiment of this invention, the controller is the core of the entire transmitter's control system. It is responsible for wireless data communication with the receiver, including the transmission of control commands and the transmission of acquired data. The controller receives the digital signal output from the independent analog-to-digital converter, extracts data characteristics, and, along with system parameters (power information, GPS information) and raw acoustic data, transmits it to the receiver via the transmitter's wireless module according to a specific data format. The receiver simultaneously receives both the transmitter and the data transmitted from it, performs relevant data algorithm processing, and, combined with the set pipe parameter information, calculates the leak location.

[0008] The beneficial effects of this invention are as follows: This invention uses GPS PPM pulses as a time synchronization reference to achieve synchronized data acquisition across all channels, ensuring accurate and reliable pipeline detection and positioning data. Adding a GPS module to the transmitter integrates positioning and ranging functions, allowing direct calculation of pipeline laying distances and eliminating the need for manual on-site pipeline length measurement – ​​a first in the industry. The transmitter incorporates a built-in leakage acoustic wave feature database, comparing real-time acquired acoustic wave data with feature samples in the database to filter out environmental interference noise and eliminate invalid interference data before relevant calculations, improving the accuracy of the calculation results. The device is equipped with a wireless communication module with a built-in frequency hopping mechanism, allowing multiple devices to operate synchronously at the same time and location; the module can automatically switch the configured carrier frequency, effectively avoiding signal interference between devices. The transmitter designed in this invention has probe expansion capabilities; the hardware interface and circuit architecture support multi-channel probe external expansion, with a maximum of 8 probes that can be connected to the entire unit. Attached Figure Description

[0009] Figure 1These are schematic diagrams of the structures of the various devices in this invention;

[0010] Figure 2 This is a schematic diagram of the receiver operation of the present invention;

[0011] Figure 3 This is a schematic diagram of the transmitter operation of the present invention. Detailed Implementation

[0012] Example 1

[0013] like Figure 1 As shown, this invention discloses an intelligent digital correlator based on GPS time synchronization. The technical solution adopted includes a receiver 000, a transmitter 100, and a transmitter 200. The receiver 000 consists of a main station system 001, a control system 002, a battery 003, a display and human-computer interaction module 004, a communication module one 005, a positioning module 006, a communication module two 007, a wireless module 008, and a wireless module antenna 009. The transmitters 100 and 200 have the same system structure, both consisting of a probe 101 and connected by precision cables. The transmitter consists of a transmitter 102, an amplification and filtering module 103, an independent analog-to-digital converter module 104, a controller 105, a transmitter positioning module 106, a transmitter GPS antenna 107, a transmitter wireless module 108, a transmitter wireless module antenna 109, and a transmitter battery module 110. The probe 101 and the amplification and filtering module 103 are connected by a precision cable connector 102. The output of the amplification and filtering module 103 is connected to the independent analog-to-digital converter module 104 to complete the conversion of analog signals to digital signals, and sends the digitized sound wave signal to the controller 105.

[0014] Example 2

[0015] like Figure 2 As shown, this invention discloses an intelligent digital correlator based on GPS time synchronization. The working process of receiver 000 is as follows: S1: The main station system 001 starts working, sets the pipe length L, pipe material, and pipe diameter, calculates the sound velocity c based on empirical parameters, initializes the GPS module, and waits for the host GSP to successfully acquire satellites. S2: Positioning module 006 is successfully acquiring satellite data and is outputting positioning data and PPS signal normally. S3: The main station system 001 broadcasts a data acquisition command to inform the transmitter 100 and the probe 101 on the transmitter 200 to start data acquisition; S4: After waiting for 500ms, the master station system 001 sends a command to obtain data from the transmitter 100 module; S5: The master station system 001 waits for the transmitter 100 to transmit the collected data to the receiver 000 via the transmitter wireless module 108 and the transmitter wireless module antenna 109 on the transmitter 100. If the data is not fully received, continue waiting. After the data is fully received, proceed to step S6. S6: Master station system 001, sends a command to obtain data from transmitter module 100; S7: The master station system 001 waits for the transmitter 200 to transmit the collected data to the receiver 000 via the transmitter wireless module 108 and the transmitter wireless module antenna 109 on the transmitter 200. If the data reception is incomplete, continue waiting. After data reception is complete, proceed to S8; S8: The main station system 001 will receive data x11 and x22 from the two probes and perform windowing processing; x1 = Hn .* x11 (1) x2 = Hn .* x22 (2) Where: Hn is an 8192-point Hanning window; (.*) operation represents dot product; S9: Perform a Fourier transform on the windowed data, that is: fx1 = fft(x1) (3) fx2 = fft(x2) (4) Where: fft() represents Fourier transform; S10: Perform frequency domain filtering on the frequency domain data Xc1 and Xc2, that is: Xc1 = Hf .* fx1 (5) Yc1 = Hf .* fx2 (6) Where: Hf represents the filter window function, Hf is even-symmetric, and its length is the same as the length of fx1; S11: Perform the cross-correlation algorithm Scxy on the frequency domain data Xc1 and Xc2, i.e.: Scxy = Yc1 .* conj(Xc1) (7) Where: conj() represents taking the conjugate, and ( .* ) operation represents the dot product operation; S12: Perform inverse FFT operation on Scxy data; scxy = ifft(Scxy) (8) S12: Perform spectral rearrangement on the scxy data, that is, swap the positions of the (0 - N / 2 - 1) and (N / 2 - N - 1) data in scxy: Y = Shiftifft(scxy) (9) S13: Find the index of the maximum point in the rearranged data abs(Y), i.e.: n = find(Y == max(abs(Y))) (10) In the formula: abs() represents taking the absolute value of Y; S14: Calculate the leak location X based on the leak point, that is: X = 0.5 * (L + n * c / Fs) (11) Where: L: is the length of the pipe; n is the delay time point calculated in the formula, n<0 indicates that the waveform of the second channel leads the waveform of the first channel, n>0 indicates that the waveform of the second channel lags the waveform of the first channel; c is the speed of sound, the speed at which sound waves propagate in different pipes; Fs is the sampling frequency of 8000Hz; S15: Display and update the graphical interface, jump to S3, and broadcast the data acquisition command.

[0016] Example 3

[0017] like Figure 3 As shown, this invention discloses an intelligent digital correlator based on GPS time synchronization. The transmitter's workflow is as follows: S1: Power on, transmitter 100 starts up, initializes host configuration parameters, starts transmitter positioning module 106 to start satellite search, satellite search is successful, continue to the next stage; S2: Wait for the receiver 000 to send the start acquisition command, loop and wait until the transmitter wireless module antenna 109 and transmitter wireless module 108 receive the acquisition command, then proceed to the next step; S3: Wait for the next PPM pulse from the transmitter wireless module 108. If the pulse arrives, proceed to the next step. S4: Controller 105 starts the independent analog-to-digital conversion module 104 to collect 8192 points in one frame. After the collection is completed, the data in one frame is analyzed and judged, and compared with the feature parameters in the built-in database to determine whether it is a water leakage sound wave signal. S5: Wait for the receiver 000 to receive the data command from the transmission probe 101. If not received, continue waiting; if the transmitter wireless module 108 receives the command, proceed to the next step S6. S6: The transmitter wireless module 108 collects 1 frame of data; the controller 105 packages the collected raw data, the analyzed water leakage sound wave characteristic data, the system power, the working status and other information, and sends them to the receiver 000 in a certain data format through the transmitter wireless module 108 and the transmitter wireless module antenna 109. S7: Send data. Continue sending data until all data has been sent, then proceed to the next step, S8. S8: Wait for the next wireless acquisition command and proceed to step S2; After receiving GPS data uploaded by transmitters 100 and 200, receiver 000 calculates the pipe length using the following method: When the pipes tested by transmitters 100 and 200 are straight lines, the pipe length is calculated based on the straight-line distance. Transmitter 100 transmits GPS coordinates as latitude. longitude Elevation Transmitter 200 sends GPS data in latitude B, longitude L, and elevation H, according to the conversion formula from geodetic coordinates to rectangular coordinates: (12) (13) (14) (15) (16) (17) In the formula: The square of the first eccentricity e of the reference ellipsoid = 0.00669438499959 (18) (12)~(14) Middle ; (19) In equation (18) Reference ellipsoid semi-major axis ; (20) , , The transmitter (200) sends the geodetic latitude, geodetic longitude, and geodetic height of the GPS. , , Spatial rectangular coordinates; conversion formula from spatial rectangular coordinates to station tangent plane coordinates: (twenty one) In the formula, ( , ) represents the geodetic latitude and longitude of the survey station (also known as the benchmark point). , , () represents the spatial rectangular coordinates of the measuring station. Thus, through the coordinate transformations in the above two steps, the GPS coordinates of a point are converted into the coordinates of the station's tangential plane. Since the pipelines are basically on the same horizontal plane, the result of formula (21) is... Calculated It should be 0. The straight-line distance between transmitter (100) and transmitter (200) is: (twenty two) When the pipeline is not straight, the transmitter (100) is taken as the reference point, that is, the GPS point of the transmitter (100) is... longitude Elevation The transmitter (200) collects a series of GPS points along the pipeline at the two probe placement points as follows: , , ),in . Substituting into formula (22), we can obtain ( , , ) (twenty three) The total distance S is obtained by summing the real-time distances every second, i.e.: ; (twenty four).

[0018] While the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and modifications or variations without creative effort are still within the protection scope of the present invention.

Claims

1. An intelligent digital correlator based on GPS time synchronization, characterized in that: It includes a receiver (000), a transmitter (100), and a transmitter (200); the receiver (000) consists of a main station system (001), a control system (002), a battery (003), a display and human-computer interaction module (004), a communication module one (005), a positioning module (006), a communication module two (007), a wireless module (008), and a wireless module antenna (009); the transmitter (100) and transmitter (200) have the same system structure, both consisting of a probe (101), a precision cable connector (102), and an amplification and filtering module (103). The transmitter consists of an independent analog-to-digital converter module (104), a controller (105), a transmitter positioning module (106), a transmitter GPS antenna (107), a transmitter wireless module (108), a transmitter wireless module antenna (109), and a transmitter battery module (110). The probe (101) and the amplification and filtering module (103) are connected by a precision cable connector (102). The output of the amplification and filtering module (103) is connected to the independent analog-to-digital converter module (104) to complete the conversion of analog signals to digital signals and send the digitized acoustic wave signals to the controller (105).

2. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The communication module 1 (005) uses a Wi-Fi-4G module to build a host local area network. The host system (001) and the wireless module (008) are connected to the local area network via a network cable.

3. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The positioning module (006) uses GPS to acquire GPS satellite data and calibrates the system clock through PPS time pulses, providing a unified clock reference for the entire system.

4. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The positioning module (006) uses a Beidou module to acquire Beidou satellite data and calibrates the system clock through PPS time pulses, providing a unified clock reference for the entire system.

5. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The second communication module (007) adopts a three-in-one high-gain antenna composed of GPS, wifi and 4G. The GPS working frequency band of the antenna is 1561±10MHz, the wifi working frequency band is 2400MHz-2500MHz, and the 4G working frequency band is 700MHz-2700MHz.

6. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The wireless module antenna (009) is a 15dB high-gain antenna with an operating frequency band of 902-928MHz and a center frequency of 915MHz.

7. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The probe (101) has a built-in precision piezoelectric sensor and a low-noise preamplifier circuit to acquire the leakage sound wave signal and amplify the first stage of the signal; the precision cable connector (102) has 4-core aviation connectors at both ends, and the 4 cores of the cable are power supply VCC, ground GND, signal SIG and control CTL respectively; the transmitter positioning module (106) adopts a GPS module, which uses the GPS output pulse PPM as a reference to provide a unified clock reference for the probe synchronous data acquisition; the transmitter GPS antenna (107) adopts a small-sized GPS antenna with a working frequency range of 1561±10MHz; the transmitter battery module (110) outputs +12V voltage.

8. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The system code IDs of the controllers (105) of transmitters (100) and (200) are different, and their GPS location information is different.

9. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The working process of the receiver (000) is as follows: S1: The main station system (001) starts working, sets the pipe length L, pipe material, and pipe diameter, calculates the sound velocity c based on empirical parameters, initializes the GPS module, and waits for the host GSP to successfully search for satellites. S2: The positioning module (006) is successfully searching for satellites and is outputting positioning data and PPS signal normally. S3: The main station system (001) broadcasts a data acquisition command to inform the transmitter (100) and the probe (101) on the transmitter (200) to start acquiring data; S4: The master station system (001) waits for 500ms and then sends a command to obtain data from the transmitter (100) module; S5: The main station system (001) waits for the transmitter (100) to transmit the collected data to the receiver (000) through the transmitter wireless module (108) and the transmitter wireless module antenna (109) on the transmitter (100); if the data has not been fully received, it continues to wait; After receiving the data, proceed to step S6; S6: The main station system (001) sends a command to obtain data from the transmitter (100) module; S7: The main station system (001) waits for the transmitter (200) to transmit the collected data to the receiver (000) through the transmitter wireless module (108) and the transmitter wireless module antenna (109) on the transmitter (200); if the data is not fully received, continue to wait; if the data is fully received, proceed to S8; S8: The main station system (001) will receive data x11 and x22 from the two probes and perform windowing processing; x1 = Hn .* x11 (1) x2 = Hn .* x22 (2) Where: Hn is an 8192-point Hanning window; (.*) operation represents dot product; S9: Perform a Fourier transform on the windowed data, that is: fx1 = fft(x1) (3) fx2 = fft(x2) (4) Where: fft() represents Fourier transform; S10: Perform frequency domain filtering on the frequency domain data Xc1 and Xc2, that is: Xc1 = Hf .* fx1 (5) Yc1 = Hf .* fx2 (6) Where: Hf represents the filter window function, Hf is even-symmetric, and its length is the same as the length of fx1; S11: Perform the cross-correlation algorithm Scxy on the frequency domain data Xc1 and Xc2, i.e.: Scxy = Yc1 .* conj(Xc1) (7) Where: conj() represents taking the conjugate, and ( .* ) operation represents the dot product operation; S12: Perform inverse FFT operation on Scxy data; scxy = ifft(Scxy) (8) S12: Perform spectral rearrangement on the scxy data, that is, swap the positions of the (0 - N / 2 - 1) and (N / 2 - N - 1) data in scxy: Y = Shiftifft(scxy) (9) S13: Find the index of the maximum point in the rearranged data abs(Y), i.e.: n = find(Y == max(abs(Y))) (10) In the formula: abs() represents taking the absolute value of Y; S14: Calculate the leak location X based on the leak point, that is: X = 0.5 * (L + n * c / Fs) (11) Where: L: is the length of the pipe; n is the delay time point calculated in the formula, n<0 indicates that the waveform of the second channel leads the waveform of the first channel, n>0 indicates that the waveform of the second channel lags the waveform of the first channel; c is the speed of sound, the speed at which sound waves propagate in different pipes; Fs is the sampling frequency of 8000Hz; S15: Display and update the graphical interface, jump to S3, and broadcast the data acquisition command.

10. The intelligent digital correlator based on GPS time synchronization according to claim 1, characterized in that: The transmitter (100) operates as follows: S1: Power on, the transmitter (100) host starts, initializes the host configuration parameters, starts the transmitter positioning module (106) to start satellite search, satellite search is successful, and continues to the next stage; S2: Wait for the receiver (000) to send the start acquisition command, and wait in a loop until the transmitter wireless module antenna (109) and transmitter wireless module (108) receive the acquisition command, and then proceed to the next stage; S3: Wait for the next PPM pulse from the transmitter wireless module (108). If the pulse arrives, proceed to the next step. S4: The controller (105) starts the independent analog-to-digital conversion module (104) to work, collect 8192 points in 1 frame. After the collection is completed, the data of 1 frame is analyzed and judged, and compared with the feature parameters of the built-in database to determine whether it is a water leakage sound wave signal. S5: Wait for the receiver (000) to receive the data command from the transmission probe (101); if not received, continue to wait; if the transmitter wireless module (108) receives the instruction, proceed to the next step S6; S6: The transmitter wireless module (108) collects data in 1 frame; the controller (105) packages the collected raw data, the analyzed water leakage sound wave characteristic data, the system power, the working status and other information, and sends them to the receiver (000) in a certain data format through the transmitter wireless module (108) and the transmitter wireless module antenna (109). S7: Send data; if data is not completely sent, continue sending data; once data transmission is complete, proceed to the next step S8. S8: Wait for the next wireless acquisition command and proceed to step S2; After receiving GPS data uploaded by transmitter 100 and GPS data from transmitter 200, receiver (000) calculates the pipe length as follows: When the pipes tested by transmitter (100) and transmitter (200) are straight, the pipe length is calculated based on the straight-line distance; transmitter (100) transmits GPS coordinates as latitude. longitude Elevation The transmitter (200) sends GPS coordinates as latitude B, longitude L, and elevation H, according to the conversion formula from geodetic coordinates to rectangular coordinates: (12) (13) (14) (15) (16) (17) In the formula: The square of the first eccentricity e of the reference ellipsoid = 0.00669438499959 (18) (12)~(14) Middle ; (19) In equation (18) Reference ellipsoid semi-major axis ; (20) , , The transmitter (200) sends the geodetic latitude, geodetic longitude, and geodetic height of the GPS. , , Spatial rectangular coordinates; conversion formula from spatial rectangular coordinates to station tangent plane coordinates: （21） In the formula, ( , ) represents the geodetic latitude and longitude of the survey station (also known as the benchmark point). , , ) represents the spatial rectangular coordinates of the measuring station; thus, through the coordinate transformation in the above two steps, the GPS coordinates of a point are converted into the coordinates of the station's center tangent plane; since the pipeline is basically in the same horizontal plane, the result of formula (21) Calculated It should be 0; The straight-line distance between transmitter (100) and transmitter (200) is: （22） When the pipeline is not straight, the transmitter (100) is taken as the reference point, that is, the GPS point of the transmitter (100) is... longitude Elevation The transmitter (200) collects a series of GPS points along the pipeline at the two probe placement points. , , ),in ; Substituting into formula (22), we can obtain ( , , ); (23) The total distance S is obtained by summing the real-time distances every second, i.e.: ； (24)。

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