Online target point window period measurement method and system based on PPK post-processing

Abstract

The application discloses an online target point sky window period measurement method and system based on PPK post-processing, and on the basis of a GNSS RTK measurement method, proposes a data solution method of PPK post-processing, can carry out the sky window period measurement of the online target point under the premise that the offline basic control network result is not obtained, and completes the target point layout, measurement and vehicle-mounted Li DAR scanning measurement work through one time of going online, effectively solves the difficulties of tight working period of business line railway re-measurement, short sky window time, great safety risk of existing line operation and the like while reducing the going online frequency of workers, compares and checks the method of the leveling actual measurement result and the fitting result, reduces the error probability of data processing, effectively guarantees the target control network result quality, and proposes a new solution method for the online target control network measurement in the re-measurement work in the railway operation period.

Description

Technical Field

[0001] This invention relates to the field of surveying and mapping technology, specifically to a method and system for measuring online target points during skylight periods based on PPK post-processing. Background Technology

[0002] Railways are the main artery of the national economy, a major project for people's livelihood, and the backbone of the comprehensive transportation system, playing a vital role in economic and social development. Faced with the large-scale modern operational railway lines, traditional resurveying methods, such as total stations and track inspection trolleys, are no longer sufficient to meet the ever-increasing demand for resurveying. While vehicle-mounted or airborne LiDAR scanning measurement technology can effectively improve the efficiency of operational railway resurveying, it requires the results of an online target control network to control the quality of the LiDAR scanning point cloud results. How to quickly and accurately deploy and acquire target control network results is a crucial factor affecting the development of LiDAR scanning measurement technology and significantly impacts the efficiency of operational railway resurveying.

[0003] Existing online target control network measurements typically employ methods such as total stations, static GNSS, and RTK, which suffer from drawbacks such as low operational efficiency, high labor costs, and the necessity to use basic control network results. These methods are insufficient to meet the needs of resurveying tasks on operational railway lines with tight schedules and short online monitoring windows. Furthermore, some resurveying tasks on operational railway lines require the simultaneous establishment of offline basic control networks, which places new demands on the adoption of measurement technologies. Summary of the Invention

[0004] This application provides a method and system for measuring online target points during track maintenance windows based on PPK post-processing, in order to solve the problems of tight schedules, short track maintenance windows, and high safety risks of existing line operations during resurveys on existing railway lines.

[0005] According to the first aspect, one embodiment provides a method for measuring online target points during skylight periods based on PPK post-processing, the method comprising:

[0006] Based on project requirements, a basic control network for the resurvey of operational railway lines was established.

[0007] During the skylight period, online target point deployment, online target point leveling, GNSS-based online target point measurement, and vehicle-mounted LiDAR scanning measurement were carried out, while offline basic control network measurement was carried out during the remaining time periods.

[0008] Based on the original measurement data of the offline basic control network, the results of the offline basic control network are obtained, and the seven parameters are calculated in segments;

[0009] Based on the raw GNSS measurement data of the online target points, the PPK post-processing calculation is performed using a seven-parameter fitting method to obtain the online target point results, which include the fitted plane coordinates and fitted elevation coordinates of the target points.

[0010] Based on the original leveling data of the online target points, the leveling elevation of the online target points is obtained through adjustment calculation. The fitted elevation of the online target points is compared with the leveling elevation to check the quality of the fitted data. It is determined whether the difference between the fitted elevation and the leveling elevation exceeds the preset threshold. If it does, the cause is identified and dealt with to obtain the final online target control network result.

[0011] Furthermore, the method also includes:

[0012] The obtained online target control network results are used to correct the POS trajectory line of the vehicle-mounted LiDAR scan, resulting in point cloud results that meet the measurement accuracy. Based on the point cloud results, the scanning measurement results of the operating railway line are obtained.

[0013] Furthermore, the offline basic control network includes an offline basic horizontal control network and an offline basic vertical control network.

[0014] Furthermore, GNSS-based online target point measurement specifically includes:

[0015] Before the start of the skylight period, a GNSS reference station is set up at the selected offline basic control point. A GNSS receiver is used to connect to the reference station and measure the coordinates of the reference station. Once the GNSS receiver is in a fixed working state, the online target point measurement work is started after the start of the skylight period.

[0016] Furthermore, GNSS-based online target point measurement specifically includes:

[0017] The online target point measurement uses a two-round operation mode. Set the parameters as required, enter the target point name, and measure the online target points in sequence.

[0018] Furthermore, based on the original measurement data of the offline basic control network, the results of the offline basic control network are obtained, and seven parameters are calculated in segments, specifically including:

[0019] The results of the offline basic control network are obtained by segmented or whole-network adjustment.

[0020] When calculating the seven parameters, the project should be divided into sections based on the actual situation. For long and narrow operating railway lines, sections of 10-15 kilometers are appropriate.

[0021] Furthermore, based on the raw GNSS measurement data of the online target points, a seven-parameter fitting method was used to perform PPK post-processing calculations to obtain the online target point results, specifically including:

[0022] The raw measurement data from the GNSS receiver is exported and converted to the same coordinate system as the results of the offline basic control network. The results of the offline basic control network include three-dimensional constrained adjustment results and three-dimensional unconstrained adjustment results. The three-dimensional unconstrained adjustment results of the base station points are used as the reference for coordinate transformation. When the matching effect of the base station results is not good, the results of the check points are used as the reference for coordinate transformation.

[0023] The data after coordinate transformation is then transformed back to a latitude and longitude coordinate system for use in seven-parameter fitting calculations.

[0024] Furthermore, based on the original measurement data of the online target point leveling survey, the leveling elevation of the online target point is obtained through adjustment calculation, specifically including:

[0025] Using the offline elevation control points as the starting or ending point, the online target points are measured and adjusted using the traverse route measurement method to obtain the online target point leveling elevation.

[0026] According to a second aspect, one embodiment provides an online target point window time measurement system based on PPK post-processing, the system comprising:

[0027] The offline basic control network deployment module is used to deploy the offline basic control network of operating railway lines based on project requirements;

[0028] The online and offline measurement modules are used to carry out online target point deployment, online target point leveling, GNSS-based online target point measurement, and vehicle-mounted LiDAR scanning measurement during the skylight period, and to carry out offline basic control network measurement during other periods.

[0029] The offline basic control network results acquisition module is used to acquire offline basic control network results based on the original measurement data of the offline basic control network, and to calculate the seven parameters in segments;

[0030] The PPK post-processing module is used to perform PPK post-processing calculations based on the raw GNSS measurement data of the online target points using a seven-parameter fitting method to obtain the online target point results. The online target point results include the fitted plane coordinates and fitted elevation of the target points.

[0031] The online target point result verification module is used to obtain the leveling elevation of the online target points through adjustment calculation based on the original leveling data of the online target points. It compares the fitted elevation of the online target points with the leveling elevation to check the quality of the fitted data, and determines whether the difference between the fitted elevation and the leveling elevation exceeds a preset threshold. If it exceeds the threshold, the cause is identified and processed to obtain the final online target control network result.

[0032] Furthermore, the method also includes:

[0033] The point cloud result quality control module is used to use the obtained online target control network results to correct the vehicle-mounted LiDAR scanning POS trajectory line, so as to obtain point cloud results that meet the measurement accuracy, and obtain the scanning measurement results on the operating railway line based on the point cloud results.

[0034] This application provides a method and system for online target point measurement during a skylight period based on PPK post-processing. During the skylight period, online target point deployment, online target point leveling, GNSS-based online target point measurement, and vehicle-mounted LiDAR scanning measurement are carried out, while offline basic control network measurement is conducted during other periods. A seven-parameter fitting method is used for PPK post-processing to calculate the online target point results. The fitted elevation of the online target points is compared with the leveling elevation to check the quality of the fitted data. It is determined whether the difference between the fitted elevation and the leveling elevation exceeds a preset threshold. If it does, the cause is identified and addressed to obtain the final online target control network results. Based on the GNSS RTK measurement method, this invention proposes a PPK post-processing data solution method. This method enables simultaneous online target point measurements during designated monitoring windows, even without obtaining the offline basic control network results. It completes target point deployment, measurement, and vehicle-mounted LiDAR scanning in a single online session. This reduces the frequency of staff on-site visits and effectively addresses challenges such as tight schedules, short monitoring windows, and high safety risks associated with existing railway line resurveys. By comparing and verifying the leveling measurement results with the seven-parameter fitting results, the probability of data processing errors is reduced, effectively ensuring the quality of the target control network results. This provides a new solution for online target control network construction measurements during railway operation resurveys. Attached Figure Description

[0035] Figure 1 A flowchart illustrating an online target point skylight period measurement method based on PPK post-processing, as provided in one embodiment of the present invention;

[0036] Figure 2 This invention provides a coordinate transformation result of the original GNSS measurement data of an online target point in a PPK post-processing-based online target point skylight period measurement method, as an embodiment of the present invention.

[0037] Figure 3 This invention provides a method for measuring online target points during a window of time based on PPK post-processing, in which PPK post-processing is used to obtain online target point results.

[0038] Figure 4 A method for measuring online target points during a skylight period based on PPK post-processing, as provided in one embodiment of the present invention, compares the leveling elevation of the target point with the fitted elevation.

[0039] Figure 5This is a schematic diagram of the logical structure of an online target point window period measurement system based on PPK post-processing, provided as an embodiment of the present invention. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0041] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0042] The first embodiment of this invention provides a method for measuring online target points during skylight periods based on PPK post-processing. The following is a combination of... Figure 1 Please provide a detailed explanation.

[0043] In step S100, the basic control network of the operating railway line is laid out based on project requirements.

[0044] Specifically, the offline basic control network includes an offline basic horizontal control network and an offline basic vertical control network. The offline basic control network serves two purposes: firstly, it provides starting data for online target control network measurements; secondly, it provides base station locations for vehicle-mounted LiDAR scanning measurements.

[0045] In step S200, during the skylight period, online target point deployment, online target point leveling, GNSS-based online target point measurement, and vehicle-mounted LiDAR scanning measurement are carried out, while offline basic control network measurement is carried out during the remaining time periods.

[0046] Online target point leveling is a method of measuring the leveling elevation of online target points using a level or spirit level.

[0047] This invention employs GNSS PPK technology and, based on the GNSS RTK measurement method, proposes a data processing method using PPK (Post-Processing Kinematic) post-processing. The GNSS-based online target point measurement specifically includes:

[0048] Before the start of the skylight period, a GNSS reference station is set up at the selected offline basic control point. A GNSS receiver is used to connect to the reference station and measure the coordinates of the reference station. Once the GNSS receiver is in a fixed working state, the online target point measurement work is started after the start of the skylight period. The online target point measurement uses a two-round operation mode. The parameters are set as required, the target point name is entered, and the online target points are measured in sequence.

[0049] The specific preparations are as follows:

[0050] 1) After setting up the GNSS base station at the selected baseline control point, connect the antenna, correctly position the altimeter and measure the base station instrument height. Create a new project in the handheld device, select the National Coordinate System 2000, set the central meridian, and leave other values ​​as default. Enter the control point name and instrument height in the handheld device, and use single-point positioning mode to collect terrain points.

[0051] 2) Setting up the base station: Use the self-starting base station - external radio mode, select RTCM3.2 differential format, and set the baud rate and altitude cutoff angle. Select the antenna height, add the single-point positioning coordinates obtained in the previous step, and the base station setup is complete after successful library selection. The instrument will automatically disconnect.

[0052] 3) Rover setup: After connecting the GNSS receiver, enter the rover setup, select Huace radio and check the protocol. The channel setting should be consistent with the base station channel, and the baud rate should be lower than the base station baud rate. After the instrument is fixed, you can start the operation.

[0053] The target point measurement work is carried out in the following specific way:

[0054] 1) Target point measurement: With the instrument fixed, enter the point measurement mode. Select control point measurement as the acquisition method, set the number of repetitions to 2, the number of measurement points to 10, set the horizontal and vertical limits, and set the delay time to 8 seconds after fixing. After setting, enter the target point number and instrument height (vertical height) and start the measurement.

[0055] 2) Checkpoint measurement: Measure at least two offline basic control points before going online and after going offline for data quality check. At the same time, they can be used to calculate the target point results in place of the base station if the base station coordinate measurement is incorrect.

[0056] The measurement work of the offline basic control network includes the measurement of the offline basic horizontal control network and the measurement of the offline basic elevation control network.

[0057] A track maintenance window is a period during which no trains are running on the railway, allowing personnel to work online. This embodiment makes full use of the brief track maintenance window period on the operating line to measure the target points online, while conducting offline control network measurements during other times. This allows for simultaneous measurement of online target points during the track maintenance window period, even before the results of the offline basic control network are obtained. Furthermore, the target point deployment, measurement, and onboard LiDAR scanning measurement can be completed in a single online operation. This effectively solves the difficulties of tight schedules, short track maintenance windows, and high safety risks associated with existing line operations, while reducing the frequency of personnel going online.

[0058] In step S300, based on the original measurement data of the offline basic control network, the results of the offline basic control network are obtained, and the seven parameters are calculated in segments.

[0059] The above steps specifically include: obtaining the results of the offline basic control network by means of segmented or whole-network adjustment; segmenting the calculation of the seven parameters according to the actual situation of the project, and for long and narrow operating railways, the segment should be 10-15 kilometers.

[0060] Specifically, the seven parameters are calculated in segments: For the resurvey of a strip-shaped operating railway line, the segments for calculating the seven parameters should not be too long. At the same time, shorter segments will increase the amount of calculation. The segment distance should be 10-15 kilometers. In areas with gentle terrain, the segment distance can be appropriately increased. The seven parameters are calculated using Hi-Target HGO software.

[0061] In step S400, based on the original GNSS measurement data of the online target points, the PPK post-processing calculation is performed using a seven-parameter fitting method to obtain the online target point results, which include the fitted plane coordinates and fitted elevation of the target points.

[0062] The above steps specifically include: exporting the raw measurement data from the GNSS receiver in the required format; organizing the data according to several parameters such as point name, point type, spatial rectangular X coordinate, spatial rectangular Y coordinate, and spatial rectangular Z coordinate; and then converting the data to the same coordinate system as the offline basic control network results. The offline basic control network results include three-dimensional constrained adjustment results and three-dimensional unconstrained adjustment results. The three-dimensional unconstrained adjustment results of the base station points are used as the reference for coordinate transformation. When the matching effect of the base station results is poor, the check point results are used as the reference for coordinate transformation. The coordinate transformation data is as follows: Figure 2 As shown; the coordinate-transformed data is then transformed back to a latitude and longitude coordinate system for seven-parameter fitting calculation. The PPK post-processing calculation yields the online target point results as shown. Figure 3 As shown.

[0063] In step S500, based on the original leveling data of the online target points, the leveling elevation of the online target points is obtained through adjustment calculation. The fitted elevation of the online target points is compared with the leveling elevation to check the quality of the fitted data. It is determined whether the difference between the fitted elevation and the leveling elevation exceeds a preset threshold. If it does, the cause is identified and processed to obtain the final online target control network result.

[0064] The target point coordinates obtained from the seven-parameter fitting include both planar and elevation coordinates. The planar coordinates have higher accuracy, but the elevation coordinates have slightly lower accuracy. By comparing and verifying the results with the leveling measurements, the probability of data processing errors is reduced, effectively ensuring the quality of the target control network results.

[0065] Specifically, taking the offline elevation control points as the starting or ending point, the online target points are measured using the traverse route measurement method and adjustment calculations are performed to obtain the online target point leveling elevation.

[0066] The fitted elevations were compared with the leveling elevations. The elevations of the statistical points were found to be poor, with some results as follows: Figure 4 As shown, under normal circumstances, the difference between the two should be less than 20mm; for sections where the difference in elevation results exceeds the limit, analyze the reasons and solve the problems.

[0067] In step S600, the obtained online target control network results are used to correct the vehicle-mounted LiDAR scanning POS trajectory line to obtain point cloud results that meet the measurement accuracy. Based on the point cloud results, the scanning measurement results on the operating railway line (including point cloud results and other data extracted from the point cloud results as required by the contract) are obtained.

[0068] By applying the online target point measurement method based on PPK post-processing of this invention to a re-survey project of an operating railway line in Inner Mongolia, the measurement of the offline basic control network and the online target control network were carried out simultaneously, which greatly shortened the task period and reduced the frequency of personnel going online. Under the premise of ensuring personnel safety, the project cost was reduced, and the quality of the target control network results was qualified, which well met the correction requirements of the vehicle-mounted LiDAR point cloud scanning data. This provides a new and efficient solution for the operation of re-survey projects of operating railway lines.

[0069] This invention provides a method for measuring online target points during railway operation windows based on PPK post-processing. It acquires offline target point results using PPK post-processing on the basis of GNSS RTK mode, overcoming the limitation of not being able to obtain offline basic control network results in advance. This fully utilizes the short operation window period of railway lines, achieving the goal of completing the measurement in a single online operation. It allows for simultaneous online and offline measurement work, accelerating project progress while effectively reducing the frequency of personnel going online and minimizing online operation accidents. This is of great significance for the efficient and safe operation of railway operation period re-measurement projects. The method of comparing and verifying the leveling measurement results with the seven-parameter fitting results reduces the probability of data processing errors and effectively ensures the quality of the target control network results.

[0070] Corresponding to the above-disclosed method for measuring online target window time periods based on PPK post-processing, this invention also discloses a system for measuring online target window time periods based on PPK post-processing, such as... Figure 5 As shown, it specifically includes:

[0071] The offline basic control network deployment module is used to deploy the offline basic control network of operating railway lines based on project requirements;

[0072] The online and offline measurement modules are used to carry out online target point deployment, online target point leveling, GNSS-based online target point measurement, and vehicle-mounted LiDAR scanning measurement during the skylight period, and to carry out offline basic control network measurement during other periods.

[0073] The offline basic control network results acquisition module is used to acquire offline basic control network results based on the original measurement data of the offline basic control network, and to calculate the seven parameters in segments;

[0074] The PPK post-processing module is used to perform PPK post-processing calculations based on the raw GNSS measurement data of the online target points using a seven-parameter fitting method to obtain the online target point results. The online target point results include the fitted plane coordinates and fitted elevation of the target points.

[0075] The online target point result verification module is used to obtain the leveling elevation of the online target point through adjustment calculation based on the original leveling data of the online target point. It compares the fitted elevation of the online target point with the leveling elevation to check the quality of the fitted data, and determines whether the difference between the fitted elevation and the leveling elevation exceeds a preset threshold. If it exceeds the threshold, the cause is identified and processed to obtain the final online target control network result.

[0076] The point cloud result quality control module is used to use the obtained online target control network results to correct the vehicle-mounted LiDAR scanning POS trajectory line, so as to obtain point cloud results that meet the measurement accuracy, and obtain the scanning measurement results on the operating railway line based on the point cloud results.

[0077] Furthermore, the PPK post-processing module is specifically used for:

[0078] The raw measurement data from the GNSS receiver is exported and converted to the same coordinate system as the results of the offline basic control network. The results of the offline basic control network include three-dimensional constrained adjustment results and three-dimensional unconstrained adjustment results. The three-dimensional unconstrained adjustment results of the base station points are used as the reference for coordinate transformation. When the matching effect of the base station results is not good, the results of the check points are used as the reference for coordinate transformation.

[0079] The data after coordinate transformation is then transformed back to a latitude and longitude coordinate system for use in seven-parameter fitting calculations.

[0080] It should be noted that for a detailed description of the online target point skylight period measurement system based on PPK post-processing provided in the embodiments of the present invention, please refer to the relevant description of the online target point skylight period measurement method based on PPK post-processing provided in the embodiments of this application, which will not be repeated here.

[0081] Those skilled in the art will understand that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to achieve the above functions. For example, the program can be stored in the memory of a device, and when the program in the memory is executed by the processor, all or part of the above functions can be achieved. In addition, when all or part of the functions in the above embodiments are implemented by computer programs, the program can also be stored in a server, another computer, disk, optical disk, flash drive, or external hard drive, etc., and can be downloaded or copied to the memory of a local device, or the system of the local device can be updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be achieved.

[0082] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the ideas of this invention.

Claims

1. A method for measuring online target points during skylight periods based on PPK post-processing, characterized in that, The method includes: Deploy the underground basic control network of the operational railway line based on project requirements; During the skylight period, online target point deployment, online target point leveling, GNSS-based online target point measurement, and vehicle-mounted LiDAR scanning measurement were carried out, while offline basic control network measurement was carried out during the remaining time periods. Based on the original measurement data of the offline basic control network, the results of the offline basic control network are obtained, and the seven parameters are calculated in segments; Based on the raw GNSS measurement data of the online target points, the PPK post-processing calculation is performed using a seven-parameter fitting method to obtain the online target point results, which include the fitted plane coordinates and fitted elevation of the target points. Based on the original data of online target point leveling measurement, the leveling elevation of the online target point is obtained through adjustment calculation. The fitted elevation of the online target point is compared with the leveling elevation to check the quality of the fitted data. It is determined whether the difference between the fitted elevation and the leveling elevation exceeds the preset threshold. If it exceeds the threshold, the cause is identified and processed to obtain the final online target control network result. in: Based on the raw GNSS measurement data of the online target points, the PPK post-processing calculation was performed using a seven-parameter fitting method to obtain the online target point results, specifically including: The raw measurement data from the GNSS receiver is exported and converted to the same coordinate system as the results of the offline basic control network. The results of the offline basic control network include three-dimensional constrained adjustment results and three-dimensional unconstrained adjustment results. The three-dimensional unconstrained adjustment results of the base station points are used as the reference for coordinate transformation. When the matching effect of the base station results is not good, the results of the check points are used as the reference for coordinate transformation. The data after coordinate transformation is then transformed back to a latitude and longitude coordinate system for use in seven-parameter fitting calculations.

2. The method for measuring online target points during a window of time based on PPK post-processing as described in claim 1, characterized in that, The method further includes: The obtained online target control network results are used to correct the POS trajectory line of the vehicle-mounted LiDAR scan, resulting in point cloud results that meet the measurement accuracy. Based on the point cloud results, the scanning measurement results of the operating railway line are obtained.

3. The method for measuring online target points during a window of time based on PPK post-processing as described in claim 1, characterized in that, The offline basic control network includes an offline basic horizontal control network and an offline basic vertical control network.

4. The method for measuring online target points during a window of time based on PPK post-processing as described in claim 1, characterized in that, GNSS-based online target point measurement specifically includes: Before the start of the skylight period, a GNSS reference station is set up at the selected offline basic control point. A GNSS receiver is used to connect to the reference station and measure the coordinates of the reference station. Once the GNSS receiver is in a fixed working state, the online target point measurement work is started after the start of the skylight period.

5. The method for measuring online target points during a window of time based on PPK post-processing as described in claim 4, characterized in that, GNSS-based online target point measurement also includes: The online target point measurement uses a two-round operation mode. Set the parameters as required, enter the target point name, and measure the online target points in sequence.

6. The method for measuring online target points during a window of time based on PPK post-processing as described in claim 1, characterized in that, Based on the original measurement data of the offline basic control network, the results of the offline basic control network are obtained, and seven parameters are calculated in segments, specifically including: The results of the offline basic control network are obtained by segmented or whole-network adjustment. When calculating the seven parameters, the project should be divided into sections based on the actual situation. For long and narrow operating railway lines, sections of 10-15 kilometers are appropriate.

7. The method for measuring online target points during a window of time based on PPK post-processing as described in claim 1, characterized in that, Based on the original measurement data of the online target point leveling survey, the leveling elevation of the online target point is obtained through adjustment calculation, specifically including: Using the offline elevation control points as the starting or ending point, the online target points are measured and adjusted using the traverse route measurement method to obtain the online target point leveling elevation.

8. A system for measuring online target points during skylight periods based on PPK post-processing, characterized in that, The system includes: The offline basic control network deployment module is used to deploy the offline basic control network of operating railway lines based on project requirements; The online and offline measurement modules are used to carry out online target point deployment, online target point leveling, GNSS-based online target point measurement, and vehicle-mounted LiDAR scanning measurement during the skylight period, and to carry out offline basic control network measurement during other periods. The offline basic control network results acquisition module is used to acquire offline basic control network results based on the original measurement data of the offline basic control network, and to calculate the seven parameters in segments; The PPK post-processing module is used to perform PPK post-processing calculations based on the raw GNSS measurement data of the online target points using a seven-parameter fitting method to obtain the online target point results. The online target point results include the fitted plane coordinates and fitted elevation of the target points. The online target point result verification module is used to obtain the leveling elevation of the online target point through adjustment calculation based on the original leveling data of the online target point. It compares the fitted elevation of the online target point with the leveling elevation to check the quality of the fitted data, and determines whether the difference between the fitted elevation and the leveling elevation exceeds a preset threshold. If it exceeds the threshold, the cause is identified and processed to obtain the final online target control network result. in: Based on the raw GNSS measurement data of the online target points, the PPK post-processing calculation was performed using a seven-parameter fitting method to obtain the online target point results, specifically including: The raw measurement data from the GNSS receiver is exported and converted to the same coordinate system as the results of the offline basic control network. The results of the offline basic control network include three-dimensional constrained adjustment results and three-dimensional unconstrained adjustment results. The three-dimensional unconstrained adjustment results of the base station points are used as the reference for coordinate transformation. When the matching effect of the base station results is not good, the results of the check points are used as the reference for coordinate transformation. The data after coordinate transformation is then transformed back to a latitude and longitude coordinate system for use in seven-parameter fitting calculations.

9. The online target point window period measurement system based on PPK post-processing according to claim 8, characterized in that, The system also includes: The point cloud result quality control module is used to use the obtained online target control network results to correct the vehicle-mounted LiDAR scanning POS trajectory line, so as to obtain point cloud results that meet the measurement accuracy, and obtain the scanning measurement results on the operating railway line based on the point cloud results.

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