A tunnel GNSS combined adjustment method of an outside control network and a traverse inside control network

Abstract

This invention discloses a method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network, belonging to the field of engineering surveying technology. It utilizes an ultra-long external directional edge to jointly adjust the external GNSS measurement results and the internal traverse measurement results. Specifically, it includes the following steps: Step 1, designing the tunnel control network; Step 2, conducting external GNSS measurements to obtain independent adjustment result files; Step 3, conducting internal traverse measurements to obtain independent adjustment results; Step 4, merging the internal and external traverse measurement results; Step 5, performing integrated joint adjustment based on the merged results. This invention, through external GNSS static measurements, internal traverse measurements, and initial data processing, converts the GNSS ou2 result files into traverse in2 adjustment files. After merging, it performs a unified network joint adjustment using consistent constraint points and employs long-edge control at the entrance and exit points to achieve integrated adjustment of the internal and external control networks, improving the overall network accuracy and reliability.

Description

Technical Field

[0001] This invention relates to the field of engineering surveying technology, and in particular to a method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network. Background Technology

[0002] Planar control surveying is a core technical step in ensuring the accurate completion of tunnels, and its accuracy directly determines the quality of tunnel construction and the tunnel's completion. Currently, tunnel planar control surveying is mainly divided into two independent stages: external control surveying and internal control surveying. External control surveying typically employs Global Navigation Satellite System (GNSS) static surveying technology; internal surveying, due to limitations imposed by satellite signal obstruction, generally uses traverse surveying technology.

[0003] In traditional technical solutions, the adjustment calculations for the GNSS control network outside the tunnel and the traverse control network inside the tunnel are carried out independently, that is: GNSS control surveying outside the tunnel relies on the advantages of satellite positioning to quickly obtain high-precision coordinates of the tunnel portal control points. However, its output files (such as ou2 format) use a dedicated GNSS surveying data structure, which includes professional data such as satellite orbit, observation epoch, and baseline calculation. These data cannot be directly applied to the traverse adjustment system inside the tunnel. Traverse surveying inside the tunnel uses equipment such as total stations to collect observations of side lengths and angles, generating traverse adjustment files in in2 format. The adjustment process is constrained only by a few common control points at the tunnel entrance and exit, and lacks effective integration of GNSS data outside the tunnel. Due to the incompatibility of data formats and the lack of uniform adjustment benchmarks between the two control networks, current engineering practice usually only uses the coordinates of the portal control points obtained by GNSS measurement as the starting data for the traverse measurement inside the tunnel, without incorporating all the observation information of the GNSS control network into the overall network adjustment. This results in insufficient redundant observations, and the accuracy and reliability of the entire network depend on the accuracy of a few starting points. It is easy to affect the tunnel breakthrough accuracy due to the transmission of errors from the starting points. Meanwhile, existing technologies lack standardized methods for efficiently converting GNSS tunnel control network results into traverse adjustment compatible formats. Engineers need to manually convert data formats, which is not only inefficient but also prone to introducing human error. Furthermore, it cannot achieve integrated constraints on tunnel entrance and exit control points, making it difficult to leverage the synergistic advantages of GNSS surveying and traverse surveying.

[0004] Furthermore, under the traditional independent adjustment mode, the accuracy matching between the control network outside and inside the tunnel is poor, and the constraints are simple when adjusting the whole network. When there is an error in the measurement data of a certain link, it is impossible to check and correct it through redundant observations, which leads to a reduction in the overall accuracy and reliability of the tunnel control network. Especially for long-distance, large-section tunnels, traditional methods are difficult to meet the engineering requirements of high-precision breakthrough.

[0005] Therefore, there is an urgent need for a joint adjustment method that can organically integrate the tunnel GNSS external control network and the traverse internal control network to solve problems such as incompatible data formats, inconsistent adjustment benchmarks, and insufficient redundant observations, so as to achieve integrated adjustment of the two control networks and improve the overall accuracy and reliability of the tunnel control network. Summary of the Invention

[0006] The purpose of this invention is to provide a method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for joint adjustment of a tunnel GNSS external control network and a traverse internal control network, which involves conducting GNSS external control surveys and traverse internal control surveys, and using an ultra-long external directional side to jointly adjust the external GNSS measurement results with the internal traverse measurement results, specifically including the following steps: Step 1: Design the tunnel control network according to the project type and tunnel length, and clarify the technical requirements; Step 2: Conduct GNSS measurements outside the tunnel according to the technical design and obtain independent adjustment results files outside the tunnel; Step 3: Conduct traverse surveys inside the tunnel according to the technical design, and process the traverse survey results inside the tunnel based on the independent adjustment results document outside the tunnel to obtain the independent adjustment results of the traverse survey inside the tunnel. Step 4: Extract the traverse measurement results from the independent adjustment results file outside the tunnel, and merge the traverse measurement results inside the tunnel and the traverse measurement results outside the tunnel; Step 5: Perform integrated adjustment of the tunnel interior and exterior based on the merged results.

[0008] Preferably, in step one, the technical requirements that need to be clearly defined in the technical design include, but are not limited to, the baseline, accuracy level, network type, starting point data, observation equipment, and data processing software for the control network inside and outside the tunnel.

[0009] Preferably, the specific process of step two is as follows: Based on the accuracy level, network type, and observation equipment requirements specified in the technical design documents, multiple GNSS receivers were used for static observation operations. During the observation process, the principle of observation in each time period was strictly followed, and the observation time period was divided according to the scale of the control network. Each time period was guaranteed to have sufficient observation duration to meet the data validity requirements. At the same time, auxiliary information including but not limited to the observation time period, satellite status and meteorological conditions was recorded. After the observation is completed, the original observation data is converted into a common data format, converting the special format data collected by the GNSS receiver into a general data format. The converted data undergoes static data processing to verify whether the accuracy of the starting point meets the usage requirements, resulting in an OU2 output file ready for use.

[0010] Preferably, in step two, the static data processing of the converted data specifically includes: Baseline data processing involves calculating the core parameters of each observed baseline and removing gross errors that occur in baseline settlement. The core parameters include, but are not limited to, coordinate increments, side lengths, and azimuth angles. Repeated baseline accuracy monitoring compares the observation structure of the same baseline at different time periods to verify the consistency and stability of baseline measurements; Complete the accuracy testing of synchronous and asynchronous loops, and verify the overall internal consistency accuracy of the network by calculating the closure error to ensure that there are no systematic errors; Unconstrained adjustment is a network-wide adjustment performed without external starting data constraints to evaluate the accuracy level of the control network itself.

[0011] Constraint adjustment is the process of performing constraint adjustment under external constraints.

[0012] Preferably, after the constraint adjustment in the static data processing is completed, the accuracy of the starting point is rechecked to see if it meets the requirements of engineering use. The reliability of the starting data is verified by comparing the deviation between the known coordinates of the starting point and the adjusted coordinates. If the accuracy of the starting point does not meet the requirements, the starting point needs to be re-selected or additional observations need to be made. If the accuracy meets the standard, all processing results will be integrated to generate an OU2 format result file containing core information including but not limited to control point coordinates, accuracy indicators, and adjustment report.

[0013] Preferably, the specific process of step three is as follows: For the field survey of the traverse inside the tunnel, a total station is used to conduct the survey in a station-by-station observation mode. During the survey, it is necessary to ensure that the instrument is accurately centered and leveled. The horizontal angle, vertical angle and side length data are obtained by using the left and right face double measurement method. At the same time, the environmental parameters inside the tunnel are recorded in detail. After the field data collection is completed, the process moves to the initial processing stage. Based on the adjustment results of the GNSS control network outside the tunnel, the starting coordinates of the traverse inside the tunnel are set, and independent adjustment calculations are carried out. Then, the side length two-dimensional correction is performed, and the side length projection correction is completed according to the tunnel projection surface requirements to ensure that the side length data is consistent with the control network benchmark. The accuracy assessment of the traverse survey inside the tunnel is carried out, with four core verification indicators: loop closure error, angular mean error, distance mean error, and relative closure error of the traverse length. After all accuracy indicators meet the specifications, information including but not limited to traverse point coordinates, observation data, correction parameters, and accuracy assessment reports is integrated to generate an in2 adjustment file that meets the accuracy standards for traverse surveying.

[0014] Preferably, the specific process of step four is as follows: Convert the GNSS measurement data outside the tunnel to the traverse adjustment data format; The ou2 result file generated by GNSS measurements is read by the conversion program; The core information related to traverse adjustment in the OU2 output file is accurately extracted using the preset data parsing rules in the conversion program. The core information is processed for format adaptation using a custom algorithm in the conversion program to generate the in2 adjustment file for the traverse measurement angles corresponding to the GNSS data outside the tunnel.

[0015] Preferably, in step four, the core information related to traverse adjustment in the ou2 result file includes, but is not limited to, the plane side length, azimuth angle and their relative accuracy.

[0016] Preferably, the specific process of step five is as follows: Merge the in2 adjustment files: Merge the in2 adjustment files of the traverse survey inside the tunnel and the in2 adjustment files of the GNSS conversion outside the tunnel according to equal precision weighting to obtain the merged in2 result; Constraint control points are determined, and based on the merged in2 results and constraint control points, traverse adjustment software is used to perform integrated adjustment of the tunnel interior and exterior to obtain GNSS and traverse joint adjustment results.

[0017] Preferably, determining the constraint control point specifically means: determining a GNSS constraint point at each of the two tunnel entrances outside the tunnel to form an ultra-long starting edge. The selection of the starting point is based on the common point of the GNSS and the traverse control point.

[0018] The technical effects and advantages of this invention are as follows: This invention provides a joint adjustment method for the tunnel GNSS external control network and the traverse internal control network, aiming to solve the problems of low accuracy and difficulty in data fusion caused by the traditional independent adjustment of internal and external control networks. This method first completes the technical design of tunnel plane control surveying, then conducts external GNSS static surveys and internal traverse surveys separately, and completes initial data processing. Using a self-developed MATLAB program, the GNSS ou2 result files are converted into traverse in2 adjustment files. After merging the two types of files, a joint adjustment of the entire network is carried out using consistent constraint points. This method incorporates redundant GNSS observation data, and its core advantages are: 1) The use of extra-long side control at the entrance and exit eliminates the risk of tunnel measurement accidents caused by insufficient directional accuracy and unstable point position when using short side traverse constraints at conventional tunnel entrances. At the same time, it significantly reduces the starting reference deviation caused by the large vertical angle of the short starting side in mountainous areas with large vertical deviation.

[0019] 2) It realizes the integrated adjustment of the control network inside and outside the tunnel, which greatly improves the accuracy and reliability of the entire network. Moreover, the data processing is highly automated and easy to operate, which has strong engineering practicality and promotion value. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of the method of the present invention.

[0021] Figure 2 This is the overall network diagram of the joint adjustment in an embodiment of the present invention.

[0022] Figure 3 This is a GNSS network diagram in an embodiment of the present invention.

[0023] Figure 4 This is a diagram of the traverse measurement network in an embodiment of the present invention.

[0024] Figure 5 This is a diagram showing the joint adjustment results in an embodiment of the present invention.

[0025] Figure 6 This is a diagram illustrating the software application of the present invention.

[0026] Figure 7 This is a diagram of the core information data of the ou2 result file generated by GNSS measurement in this embodiment of the invention.

[0027] Figure 8 This is a data graph showing the core information data of the ou2 result file in this embodiment of the invention after being extracted and processed by MATLAB.

[0028] Figure 9 This is a data diagram from the adjustment file of the tunnel traverse measurement in2 in an embodiment of the present invention.

[0029] Figure 10 This is a data diagram from the adjustment file of the tunnel traverse measurement in2 in an embodiment of the present invention.

[0030] Figure 11 This is a data diagram of the combined adjustment files of the in2 data for the traverse measurement inside and outside the tunnel in this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides, for example Figures 1-11 The method shown is a joint adjustment method for the external GNSS control network and the internal traverse control network of a tunnel. Based on the tunnel plane control survey scheme, GNSS external control surveys and internal traverse control surveys are carried out. The GNSS control network results are converted from the OU2 results file of the GNSS static survey into the in2 adjustment file of the traverse survey using a self-developed MATLAB program. The in2 adjustment files of the traverse survey are merged, and the external GNSS measurement results and the internal traverse survey results are jointly adjusted using an ultra-long external directional edge. The specific steps include: Step 1: Design the tunnel plane control network measurement technology. The technical design should clearly define the reference, accuracy level, network type, starting point data, observation equipment, and data processing software for the control network inside and outside the tunnel.

[0033] First, clarify the control network datum: calculate whether the projection distortion of the design projection system meets the requirements. If it does not, establish an independent coordinate system for the tunnel project, using the tunnel center meridian as the central meridian of the projection surface, and the average elevation of the tunnel track surface or road surface as the design elevation of the projection surface to reduce length distortion and meet the tunnel breakthrough accuracy requirements. Specifically, when selecting the projection elevation surface, calculate the difference between the length of the measuring edge referred to this projection elevation surface and the length of the measuring edge on the Gaussian projection surface. Compare this length difference with the control network datum, and select a projection elevation surface that meets the requirements based on the comparison results (if the difference is greater than the corresponding value of the control datum, then it is determined that the requirements are not met). The formula for calculating the length of the measuring edge referred to the projection elevation surface is:

[0034] In the formula, To calculate the distance measurement side length on the projected elevation surface, The horizontal distance on the average elevation surface at both ends of the measuring side is denoted as . The elevation of the projection surface of the independent coordinate system for tunnel engineering. The horizontal distance elevation between the two endpoints of the measuring side is given. The radius of curvature of the normal section of the reference ellipsoid along the measuring side; The formula for calculating the length of the measuring side on the Gaussian projection plane is:

[0035] In the formula, Let be the length of the measuring side on the Gaussian projection plane. To measure the distance from the midpoint of the side to the central meridian, This represents the increment of the x-coordinates of the two endpoints of the measuring side. The average radius of curvature of the midpoint of the ranging edge on the reference ellipsoid; Then, the accuracy level is determined: taking into account the scale of the project and the high-precision requirements of special scenarios such as railways, the accuracy level of the GNSS control network outside the tunnel and the traverse control network inside the tunnel is determined according to the tunnel length and specifications; in tunnel projects with opposite excavation and central connection, the technical requirements for tunnel plane control measurement are shown in the table below.

[0036]

[0037] Secondly, the network structure should be clearly defined: the external GNSS network should adopt a network-connected structure to improve network strength and reliability. Each tunnel entrance should have 3-4 control points with mutual visibility. During network design, 6-8 control points at the entrance and exit must form a synchronous direct observation system, with no fewer than 2 observation periods per ring, forming a stable and reliable GNSS network lock. Control points should be stable and reliable entry points, preferably located in the middle of the entrance and exit control points to allow for more adjustment checks during traverse surveying. The specific layout should meet the following requirements: 1. The control network outside the tunnel should be laid out in a polygonal combination pattern along the line connecting the two tunnel entrances to form a closed check condition; the control points at the entrance and exit should be connected by the direct observation side to form a long-side control network to enhance the strength of the pattern. 2. Control points should be located in places with open views, good visibility, firm soil, and that are not easily damaged; 3. The line of sight should be at least 1 meter away from the obstacle. When crossing water or sand, the line of sight should be increased appropriately. 4. For mountain stations with difficult terrain and dense forests, the site should be cleared and leveled to facilitate observation.

[0038] Closed traverse loops or crossed double traverses are laid inside the tunnel to increase the verification conditions. The specific layout must meet the following requirements: 1. The side length of the conductor inside the tunnel should be laid out according to the length of the survey design. When the side length is shorter than 200m, reinforcement measures should be taken. 2. The traverse lines inside the tunnel should be laid out in polygonal closed loops, with each loop consisting of 4 to 6 sides. Long tunnels should be laid out in intersecting double traverse loops, and the points of the intersecting double traverse lines should be staggered in front and behind. 3. Traverse points should be located in places with minimal construction interference, stable and reliable, and convenient for station setup and storage. The line of sight should be at least 0.2m away from the tunnel wall or facilities inside the tunnel. 4. For parallel twin-tunnel tunnels, it is advisable to set up traverse points at the cross passage between the two tunnels for joint measurement to form a traverse network.

[0039] At the same time, the technical specifications of observation equipment such as GNSS receivers and total stations should be clearly defined to ensure that the accuracy of the equipment matches the control network level; among them, the frequency band of GNSS receivers is generally multi-mode and multi-frequency, the observations include at least carrier phase and pseudorange, the number of receivers for synchronous observation is not less than 2, and the antenna is generally selected as earth type; The functional requirements of the data processing software should be clearly defined, and it should support core operations such as baseline calculation, adjustment calculation, and accuracy assessment, so as to provide a comprehensive and standardized technical basis for subsequent tunnel and cavern measurement work.

[0040] The basic technical requirements for satellite positioning and measurement operations are shown in the table below:

[0041] The main technical requirements for traverse surveying are shown in the table below:

[0042] Step two involves conducting GNSS measurements and data processing outside the tunnel according to the technical design. First, relying on the accuracy level, network type, and observation equipment requirements specified in the technical design documents, multiple GNSS receivers are used for static observation. During the observation process, the principle of time-period observation is strictly followed (the points observed in each time period are determined by the technical design, which is crucial to the tightness of the network structure and cannot be arbitrarily adjusted. For example, in the first time period, four control points are observed at the entrance and four at the inclined shaft, meaning eight control points are observed simultaneously for 1-2 hours; repeated observation in a time period means measuring twice within that time period; in the next time period, the four points at the inclined shaft remain stationary, and then three to four points at the exit or the next inclined shaft are measured). Observation time periods are divided according to the scale of the control network (the scale of GNSS measurements in a tunnel mainly comes from having two entrances and N inclined shafts, the number of control points at each entrance or inclined shaft, and the simultaneous connection of several points from adjacent entrances to form time periods). Sufficient observation time is ensured for each time period to meet data validity requirements. Simultaneously, auxiliary information such as the observation time period, satellite status, and meteorological conditions are recorded to provide a complete basis for subsequent data processing.

[0043] After observation, the raw observation data is first converted to a common format, transforming the receiver-acquired data in its proprietary format to facilitate subsequent static data processing. Static data processing is carried out step-by-step according to a standardized workflow: The first step is to process the baseline data, calculate the core parameters such as the coordinate increment, side length and azimuth of each observation baseline, and remove gross errors that occur in the baseline calculation. The second step is to conduct repeated baseline accuracy testing, comparing the observation results of the same baseline at different time periods to verify the consistency and stability of the baseline measurements; In GNSS network baseline processing, the length difference of the remeasured baseline should not meet the following conditions:

[0044] In the formula, Indicates a difference in length, in millimeters; This indicates the baseline measurement error, expressed in millimeters. Errors in GNSS network baseline measurements The calculation formula is:

[0045] In the formula, Fixed error, in millimeters; This is the proportional error coefficient, in millimeters; The baseline length and the distance between adjacent points are in kilometers; and the accuracy grading is shown in the table below:

[0046] The third step is to complete the accuracy testing of the synchronous loop and asynchronous loop, and verify the overall internal consistency accuracy of the network by calculating the closure error to ensure that there are no systematic errors. Among them, the GNSS network field baseline processing results include the coordinate closure error of the asynchronous loop or traverse route and the closure error of each coordinate component. , , The following conditions must be met:

[0047]

[0048]

[0049]

[0050]

[0051] If only two synchronization edges in a three-sided synchronization loop have independent results, the result of the third synchronization edge should be the algebraic sum of the other two edges. When the result of the third synchronization edge and the algebraic sum of the other two edges are frequently not zero, , , It should meet the following requirements:

[0052]

[0053]

[0054] In the formula, Measurement error in the baseline; , , represents the closure difference of each coordinate component, in millimeters; n is the number of closed loop edges; The coordinate closure error of the conforming route is expressed in millimeters. For synchronous observation periods of 4 or more stations, after processing the observations of each side, all possible loop closure errors should be checked; The fourth step is to implement unconstrained adjustment, which involves adjusting the entire network without external starting data constraints, and evaluating the accuracy level of the control network itself. Specifically, the GNSS network adjustment includes: The overall adjustment should be performed in the 2000 National Geodetic Coordinate System or the International Earth Reference Frame (ITRF); when the epochs of each subgrid are different, a unified reduction should be performed using plate tectonics models and velocity fields. In the overall adjustment, the total variance-covariance matrix of the starting point should be introduced and multiplied by an appropriate relaxation factor for weighting; The overall adjustment should include a post-hoc unit weight variance factor. The significance of the transformation parameters should be tested; after testing, insignificant transformation parameters should be eliminated and the adjustment should be performed again. After adjustment, the following should be output: geodetic coordinates of each point in the 2000 National Geodetic Coordinate System, geocentric coordinate components and geodetic coordinate components of each baseline, corrections for each baseline, adjustment values ​​and their accuracy, etc. After adjustment, the accuracy of the GNSS network should meet the relevant regulations.

[0055] Meanwhile, after the baseline vector check meets the requirements, the three-dimensional baseline vector and its corresponding variance-covariance are used as observation information, and the three-dimensional coordinates of a point are used as the starting point for calculation. Unconstrained adjustment is performed, and the three-dimensional coordinates of each point, each baseline vector and its correction and accuracy are output. In unconstrained adjustment, the absolute value of the corrections to the baseline components. It should meet the following requirements:

[0056]

[0057]

[0058] The fifth step is to carry out constrained adjustment, which involves completing the constrained adjustment work under external constraints. Specifically, this means introducing the import and export starting point data selected in the technical design and constraining the entire network to a unified coordinate datum. In the overall adjustment process, the baseline vectors after unconstrained adjustment should be used in the 2000 National Geodetic Coordinate System for either three-dimensional or two-dimensional constrained adjustment. The adjustment results should include the three-dimensional or two-dimensional coordinates in the corresponding coordinate system, baseline vector corrections, baseline side lengths, azimuths, transformation parameters, and their corresponding accuracy. In constrained adjustment, the absolute value of the difference between the baseline component corrections and the corresponding corrections for the same baseline in the unconstrained adjustment result after gross error removal is considered. It should meet the following requirements:

[0059]

[0060]

[0061] The main technical requirements for the satellite positioning and measurement control network are shown in the table below:

[0062] It should be noted that when the baseline length is less than 500m, the mean square error of the side length for first, second, and third order should be less than 5mm, the mean square error of the side length for fourth order should be less than 7.5mm, and the mean square error of the side length for fifth order should be less than 10mm.

[0063] After the adjustment is completed, the key is to check whether the accuracy of the starting point meets the needs of the project. The reliability of the starting data is verified by comparing the deviation between the known coordinates of the starting point and the adjusted coordinates. If the accuracy of the starting point does not meet the requirements, the starting point needs to be re-selected or supplemented observations need to be made. If the accuracy meets the standards, all processing results are integrated to generate an OU2 format result file containing core information such as control point coordinates, accuracy indicators, and adjustment report. This file serves as the final result of the GNSS control network outside the tunnel, providing basic data support for subsequent data format conversion and joint adjustment work.

[0064] Step 3: Field surveying and initial data processing of the traverse within the tunnel. A total station is used to measure the traverse station by station within the tunnel. Based on the results of the GNSS survey outside the tunnel (referring to using GNSS results alone, selecting a short side at the tunnel entrance, and performing independent constraint adjustment of the traverse network without GPS network, the purpose being to check accuracy and perform distance corrections), independent adjustment and side length corrections are performed. The accuracy of the traverse surveying within the tunnel is then evaluated (specifically including loop closure error, angle error, distance error, and relative closure error along the entire traverse length). After all steps are completed, a traverse surveying adjustment file (in2) is generated, showing that the internal accuracy meets the correction requirements. The field surveying and initial data processing of the traverse within the tunnel were carried out strictly in accordance with the technical design requirements of the tunnel's horizontal control network. During the field surveying phase, a high-precision total station was used to conduct the traverse survey in a station-by-station observation mode. During measurement, it was essential to ensure accurate instrument centering and leveling. Horizontal angles, vertical angles, and side lengths were obtained using both left- and right-face measurement methods. Simultaneously, environmental parameters such as temperature, humidity, and air pressure within the tunnel were recorded in detail to provide a basis for subsequent side length corrections. During the observation process, closed traverse loops or intersecting double traverse networks were prioritized to ensure the control network had sufficient verification conditions. Station verification was conducted immediately after each observation to avoid gross errors introduced by instrumental or operational mistakes. After the field data collection is completed, the process moves to the initial processing stage. First, based on the adjustment results of the GNSS control network outside the tunnel, the starting coordinates of the traverse inside the tunnel are set (taking a short side outside the tunnel, and performing initial adjustment in the same way as conventional traverse adjustment), and independent adjustment calculations are carried out. Then, the side length two-dimensional correction is performed, and the side length projection correction is completed according to the tunnel projection surface requirements to ensure that the side length data is consistent with the control network benchmark. After completing the adjustment and correction, the focus is on evaluating the accuracy of the traverse survey within the tunnel. The core verification includes four indicators: loop closure error, angular mean square error, distance mean square error, and relative closure error along the entire traverse length. Each indicator must strictly meet the accuracy requirements of the technical design. If any exceedances are found, the cause must be analyzed promptly, and supplementary or remeasurement should be organized. Once all accuracy indicators meet the specifications, all information, including traverse point coordinates, observation data, correction parameters, and accuracy evaluation reports, is integrated to generate an internally accurate traverse survey adjustment file (in2). This lays a solid data foundation for subsequent merging and joint adjustment of data from inside and outside the tunnel. Step four involves converting the GNSS measurement data outside the tunnel into the traverse adjustment data format. The core of this conversion is to build a dedicated conversion program using MATLAB software. First, the program reads the ou2 result file generated by the GNSS measurement. This file contains various types of data, including satellite observations, baseline calculations, and adjustment results. The program uses preset data parsing rules to accurately extract the core information related to the traverse adjustment, focusing on identifying three key parameters: "plane side length, azimuth angle and their relative accuracy," and removing redundant irrelevant data such as satellite orbits and observation epochs. Subsequently, a custom algorithm was used to adapt the extracted core data to a suitable format: the planar side lengths and azimuth data calculated by GNSS were converted into a format recognizable by the traverse adjustment system, while retaining relative accuracy information as the basis for subsequent weighting. This ensured that the converted data not only met the structural requirements of the in2 adjustment file but also fully preserved the high-precision characteristics of GNSS measurements. Finally, an in2 adjustment file for traverse side lengths and azimuths corresponding to the external GNSS data was generated, achieving data format unification between the external GNSS results and the internal traverse results, thus removing format compatibility obstacles for the subsequent merging and joint adjustment of the two types of data. Figures 7-8 As shown; Step 5, as Figures 9-1As shown, the GNSS traverse network data outside the tunnel and the traverse network data inside the tunnel are merged. The in2 adjustment files of the traverse measurement inside the tunnel and the in2 adjustment files converted from GNSS outside the tunnel are merged according to equal or unequal precision weighting. In this embodiment, equal precision weighting is used. The second-order GNSS control network is used outside the tunnel, and the second-order tunnel traverse control network is used inside the tunnel. Then, the integrated adjustment inside and outside the tunnel is performed. The merged in2 adjustment file is used, and a GNSS constraint point is fixed on each side outside the tunnel to form an ultra-long starting edge. The starting point is selected from the common point of GNSS and traverse control points. The integrated adjustment inside and outside the tunnel is performed using traverse adjustment software. In this embodiment, the test case uses JJ01-PSD1 with a length of 4836m through the long side. The weakest difference between the final adjustment result and the reliable independent one-way adjustment result is ΔX=2.7mm and ΔY=0mm, which verifies the reliability of the result.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network, characterized in that, Conducting GNSS control surveys outside the tunnel and traverse control surveys inside the tunnel, and using an ultra-long external directional side to jointly adjust the GNSS survey results outside the tunnel and the traverse survey results inside the tunnel, specifically including the following steps: Step 1: Design the tunnel control network according to the project type and tunnel length, and clarify the technical requirements; Step 2: Conduct GNSS measurements outside the tunnel according to the technical design and obtain independent adjustment results files outside the tunnel; Step 3: Conduct traverse surveys inside the tunnel according to the technical design, and process the traverse survey results inside the tunnel based on the independent adjustment results document outside the tunnel to obtain the independent adjustment results of the traverse survey inside the tunnel. Step 4: Extract the traverse measurement results from the independent adjustment results file outside the tunnel, and merge the traverse measurement results inside the tunnel and the traverse measurement results outside the tunnel; Step 5: Perform integrated adjustment of the tunnel interior and exterior based on the merged results.

2. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 1, characterized in that, In step one, the technical requirements that need to be clearly defined in the technical design include, but are not limited to, the baseline, accuracy level, network type, starting point data, observation equipment, and data processing software for the control network inside and outside the tunnel.

3. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 1, characterized in that, The specific process of step two is as follows: Based on the accuracy level, network type, and observation equipment requirements specified in the technical design documents, multiple GNSS receivers were used for static observation operations. During the observation process, the principle of observation in each time period was strictly followed, and the observation time period was divided according to the scale of the control network. Each time period was guaranteed to have sufficient observation duration to meet the data validity requirements. At the same time, auxiliary information including but not limited to the observation time period, satellite status and meteorological conditions was recorded. After the observation is completed, the original observation data is converted into a common data format, converting the special format data collected by the GNSS receiver into a general data format. The converted data undergoes static data processing to verify whether the accuracy of the starting point meets the usage requirements, resulting in an OU2 output file ready for use.

4. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 3, characterized in that, In step two, the static data processing of the converted data specifically includes: Baseline data processing involves calculating the core parameters of each observed baseline and removing gross errors that occur in baseline settlement. The core parameters include, but are not limited to, coordinate increments, side lengths, and azimuth angles. Repeated baseline accuracy monitoring compares the observation structure of the same baseline at different time periods to verify the consistency and stability of baseline measurements; Complete the accuracy testing of synchronous and asynchronous loops, and verify the overall internal consistency accuracy of the network by calculating the closure error to ensure that there are no systematic errors; Unconstrained adjustment is a network-wide adjustment performed without external starting data constraints to evaluate the accuracy level of the control network itself. Constraint adjustment is the process of performing constraint adjustment under external constraints.

5. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 4, characterized in that, After the constraint adjustment in the static data processing is completed, the accuracy of the starting point is rechecked to see if it meets the requirements of engineering use. The reliability of the starting data is verified by comparing the deviation between the known coordinates of the starting point and the adjusted coordinates. If the accuracy of the starting point does not meet the requirements, the starting point needs to be re-selected or additional observations need to be made. If the accuracy meets the standard, all processing results will be integrated to generate an OU2 format result file containing core information including but not limited to control point coordinates, accuracy indicators, and adjustment report.

6. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 1, characterized in that, The specific process of step three is as follows: For the field survey of the traverse inside the tunnel, a total station is used to conduct the survey in a station-by-station observation mode. During the survey, it is necessary to ensure that the instrument is accurately centered and leveled. The left-face and right-face observation methods are used to obtain the horizontal angle, vertical angle and side length data. At the same time, the environmental parameters inside the tunnel are recorded in detail. After the field data collection is completed, the process moves to the initial processing stage. Based on the adjustment results of the GNSS control network outside the tunnel, the starting coordinates of the traverse inside the tunnel are set, and independent adjustment calculations are carried out. Then, the side length two-dimensional correction is performed, and the side length projection correction is completed according to the tunnel projection surface requirements to ensure that the side length data is consistent with the control network benchmark. The accuracy assessment of the traverse survey inside the tunnel is carried out, with four core verification indicators: loop closure error, angular mean error, distance mean error, and relative closure error of the traverse length. After all accuracy indicators meet the specifications, information including but not limited to traverse point coordinates, observation data, correction parameters, and accuracy assessment reports is integrated to generate an in2 adjustment file that meets the accuracy standards for traverse surveying.

7. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 1, characterized in that, The specific process of step four is as follows: Convert the GNSS measurement data outside the tunnel to the traverse adjustment data format; The ou2 result file generated by GNSS measurements is read by the conversion program; The core information related to traverse adjustment in the OU2 output file is accurately extracted using the preset data parsing rules in the conversion program. The core information is processed for format adaptation using a custom algorithm in the conversion program to generate the in2 adjustment file for the traverse measurement angles corresponding to the GNSS data outside the tunnel.

8. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 7, characterized in that, In step four, the core information related to traverse adjustment in the ou2 result file includes, but is not limited to, plane side length, azimuth angle and their relative accuracy.

9. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 1, characterized in that, The specific process of step five is as follows: Merge the in2 adjustment files: Merge the in2 adjustment files of the traverse survey inside the tunnel and the in2 adjustment files of the GNSS conversion outside the tunnel according to equal precision weighting to obtain the merged in2 result; Constraint control points are determined, and based on the merged in2 results and constraint control points, traverse adjustment software is used to perform integrated adjustment of the tunnel interior and exterior to obtain GNSS and traverse joint adjustment results.

10. The method for joint adjustment of the tunnel GNSS external control network and the traverse internal control network according to claim 9, characterized in that, Specifically, determining the constraint control points means: determining a GNSS constraint point at each of the two tunnel entrances outside the tunnel to form an ultra-long starting edge. The starting point is selected from the common points of the GNSS and traverse control points.

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