A reference station network coordinate encryption method based on single-reference station VRS technology

Abstract

This invention proposes a reference station network coordinate encryption method based on single-reference-station VRS technology, belonging to the field of satellite navigation and high-precision positioning. The specific process is as follows: The reference station GNSS receiver receives non-differential pseudorange observation data and non-differential carrier phase observation data broadcast by GNSS satellites, forming non-differential observation equations for pseudorange and carrier phase; based on the non-differential pseudorange and carrier phase observation equations, the non-differential error corrections for the pseudorange and carrier phase observations of a single reference station in the reference station network are obtained; based on the principle of spatial correlation of atmospheric errors, during the generation of a single VRS, it is assumed that the atmospheric errors of the actual reference station and the VRS to be generated are consistent. Using the non-differential error corrections of the single reference station, the accurate coordinates of the VRS to be generated, and the satellite position, virtual pseudorange and carrier phase observations are generated to replace the actual reference station, thereby achieving reference station network coordinate encryption; thus protecting the real-time data of the reference station network.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation and high-precision positioning, and specifically relates to a method for encrypting reference station network coordinates based on single reference station VRS technology. Background Technology

[0002] The Continuous Operational Reference System (CORS) is a crucial spatial data infrastructure in my country, integrating advanced technologies such as satellite positioning, computer networking, and digital communication. It not only establishes and maintains a baseline framework for urban mapping but also provides high-precision time and space information automatically, around the clock, and in real-time. This meets the precise positioning and navigation requirements of various industries and users, and is directly applied to modern information management scenarios such as urban planning, land surveying, cadastral management, urban and rural construction, environmental monitoring, and disaster prevention and mitigation.

[0003] The positioning accuracy of the Global Navigation Satellite System (GNSS) is difficult to improve effectively due to observation errors. High-precision positioning relies on error correction information provided by a reference station network.

[0004] There are two main technical approaches to processing reference station networks. One is the regional augmentation positioning method, primarily represented by Network Real-Time Kinematic (NRTK), which generates Observable Space Representation (OSR) error correction information to directly correct errors in user observations. The other is the global augmentation positioning method, represented by PPP-RTK, which generates State Space Representation (SSR) correction information to classify and correct user errors. Precise orbit and clock bias, as well as uncalibrated phase delay (UPD), in the SSR corrections are generated from globally distributed stations, while high-precision atmospheric correction information must rely on the regional reference station network. Reference station networks can improve GNSS positioning accuracy to decimeter, centimeter, or even millimeter levels. High-precision orbit estimation also depends on the reference station network, making it a crucial infrastructure for national, regional, and global high-precision spatiotemporal benchmarks. High-precision positioning and precise orbit determination rely on the accurate coordinates of reference stations, making it impossible to maintain the confidentiality of these coordinates. Due to the need to protect real-time data from reference station networks, it is difficult to provide open services to enable data exchange and joint processing between reference station networks of different levels. Therefore, encrypting reference station network coordinates is an important measure to promote the secure application of reference station data and a crucial foundation for users to achieve high-precision enhanced positioning and precise orbit determination services.

[0005] With the development of satellite navigation systems, especially the use of the BeiDou-3 satellite system, the increase in frequency signals and the number of usable observations has enabled reference station networks to provide better reliability and availability, which will promote the construction of reference station networks. As of January 2017, China had established more than 6,000 continuously operating reference stations of different levels, which can fully support high-precision augmented positioning. However, there is also the problem of uneven distribution, with reference stations generally showing a denser distribution in the southeast than in the northwest. Due to the confidentiality of reference station coordinates, it is difficult to carry out unified organization and coordination among reference station networks at all levels.

[0006] Therefore, developing a reference station network coordinate encryption method based on single reference station VRS technology is of great significance for keeping the reference station location confidential and protecting the real-time data of the reference station network. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention proposes a reference station network coordinate encryption method based on single reference station VRS technology, building upon the existing reference station network VRS generation. This method can ensure the confidentiality of reference station positions, protect the real-time data of the reference station network, effectively solve the consistency problem of observation errors after reference station position offset, and at the same time, the high-precision positioning and precise orbit calculation performance will not be affected.

[0008] A method for encrypting reference station network coordinates based on single reference station VRS technology includes the following steps:

[0009] Step 1: The reference station's GNSS receiver receives the differential pseudorange and differential carrier phase observation data broadcast by the GNSS satellite. Using the GNSS satellite pseudorange and carrier phase observations, the differential pseudorange and carrier phase observation equations are derived.

[0010] Step 2: Based on the pseudorange non-differential observation equation and the carrier phase non-differential observation equation, obtain the non-differential error correction of the pseudorange and carrier phase observation values ​​of a single reference station in the reference station network.

[0011] Step 3: Based on the principle of spatial correlation of atmospheric errors, virtual observations of pseudorange and carrier phase are generated to replace the actual reference station by using the non-difference error correction of a single reference station, the accurate coordinates of the VRS to be generated, and the satellite position.

[0012] The specific process is as follows:

[0013] Step 1: Each GNSS satellite broadcasts non-differential pseudorange observation data and non-differential carrier phase observation data to the GNSS receiver at the reference station.

[0014] The equation for the unequal pseudorange observations of GNSS satellites received by the reference station GNSS receiver is:

[0015]

[0016] The equation for the unequal carrier phase observation of GNSS satellites received by the reference station GNSS receiver is:

[0017]

[0018] In the formula, For satellites; For receiver; Assign frequency numbers; and These are pseudorange and carrier phase observations, respectively. The geometric distance between the satellite and the receiver; and These are the receiver and satellite clock errors, respectively, in meters (m). The tropospheric wet delay of the signal propagation path is corrected using the Saastamoinen model; This is the frequency-dependent ionospheric delay amplification factor. Indicates the L1 frequency tilted path ionospheric delay; For frequency The wavelength; For carrier phase ambiguity; For the hardware delay at the receiver end, Due to hardware latency at the satellite end, express and ; and These represent the observation noise and unmodeled error corresponding to the pseudorange and carrier phase observations, respectively. Furthermore, GNSS observations are also affected by error terms such as antenna phase center offset and variation, phase entanglement, relativistic effects, and tidal corrections, which have been corrected using existing accurate models.

[0019] Step 2: According to the formula Japanese style The non-difference error corrections for the pseudorange and carrier phase observations of a single reference station A in the reference station network can be expressed as:

[0020]

[0021]

[0022] In the formula, and These are the pseudorange and carrier non-difference error corrections for reference station A, respectively. and These are pseudorange and carrier phase observations, respectively. For satellites; For reference only; Assign frequency numbers; For receiver; The geometric distance between the satellite and the receiver; and These are the receiver and satellite clock errors, respectively, in meters (m). The tropospheric wet delay is the signal propagation path. This is the frequency-dependent ionospheric delay amplification factor; Indicates the L1 frequency tilted path ionospheric delay; For frequency The wavelength; For carrier phase ambiguity; For the hardware delay at the receiver end, Due to hardware latency at the satellite end, express and .

[0023] Step 3: Based on the principle of spatial correlation of atmospheric errors, when generating a single VRS, it is assumed that the atmospheric errors of the actual reference station and the VRS to be generated are consistent. Using the non-difference error correction of the single reference station, the accurate coordinates of the VRS to be generated, and the satellite position, pseudorange and carrier phase virtual observations are generated to replace the actual observations of the original reference station.

[0024] Virtual Reference Station Up to satellite No. The VRS pseudorange and carrier phase observations at a frequency can be expressed as:

[0025]

[0026]

[0027] In the formula, and These are the pseudorange and carrier non-difference error corrections for reference station A, respectively. They can be obtained directly from the observations of reference A, or by interpolating the combined error corrections of VRS from multiple surrounding reference stations. The exact coordinates of the VRS to be generated. The satellite position is obtained by iteratively using the broadcast ephemeris at the reference station observation time.

[0028] Therefore, the reference station network coordinate encryption method based on single reference station VRS technology described above has the following technical effects:

[0029] (1) Based on the existing reference station network VRS generation, this invention proposes a reference station network coordinate encryption method based on single reference station VRS technology. This method simplifies the data processing flow and improves the calculation efficiency. Compared with the traditional reference station network VRS generation, this invention is based on a single reference station framework, which avoids the joint processing of multi-station data.

[0030] (2) This invention can effectively solve the problem of consistency of observation error after the reference station position shifts, and at the same time can meet the requirements of high-precision positioning and precise orbit determination;

[0031] (3) The present invention uses the VRS generated by a single reference station to replace the actual reference station to keep the location of the reference station confidential, thereby protecting the real-time data of the reference station network and promoting the application of reference station data security. Attached Figure Description

[0032] Figure 1 This is a flowchart of a reference station network coordinate encryption method based on single reference station VRS technology according to the present invention;

[0033] Figure 2 Generate a schematic diagram for VRS observations;

[0034] Figure 3 A distribution map of 126 stations worldwide;

[0035] Figure 4 A graph showing the deviation of the positioning results before and after the position shift of the ARUC and BRST stations;

[0036] Figure 5 RMS deviation diagram of positioning results before and after reference station position offset;

[0037] Figure 6 This is a graph showing the difference in convergence time before and after the reference station's position shift.

[0038] Figure 7 For reference station distribution map;

[0039] Figure 8 Time series plot of user positioning deviation at different offset distances from the reference station;

[0040] Figure 9 RMS plot of user positioning accuracy deviation at different offset distances from the reference station;

[0041] Figure 10 This is a diagram showing the deviation in orbit determination accuracy before and after the station offset. Detailed Implementation

[0042] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0043] A method for encrypting reference station network coordinates based on single reference station VRS technology, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps:

[0044] Step 1: Each GNSS satellite broadcasts non-differential pseudorange observation data and non-differential carrier phase observation data to the GNSS receiver at the reference station.

[0045] The equation for the unequal pseudorange observations of GNSS satellites received by the reference station GNSS receiver is:

[0046]

[0047] The equation for the unequal carrier phase observation of GNSS satellites received by the reference station GNSS receiver is:

[0048]

[0049] In the formula, For satellites; For receiver; Assign frequency numbers; and These are pseudorange and carrier phase observations, respectively. The geometric distance between the satellite and the receiver; and These are the receiver and satellite clock errors, respectively, in meters (m). The tropospheric wet delay of the signal propagation path is corrected using the Saastamoinen model; This is the frequency-dependent ionospheric delay amplification factor. Indicates the L1 frequency tilted path ionospheric delay; For frequency The wavelength; For carrier phase ambiguity; For the hardware delay at the receiver end, Due to hardware latency at the satellite end, express and ; and These represent the observation noise and unmodeled error corresponding to the pseudorange and carrier phase observations, respectively. Furthermore, GNSS observations are also affected by error terms such as antenna phase center offset and variation, phase entanglement, relativistic effects, and tidal corrections, which have been corrected using existing accurate models.

[0050] Step 2: According to the formula Japanese style The non-difference error corrections for the pseudorange and carrier phase observations of a single reference station A in the reference station network can be expressed as:

[0051]

[0052]

[0053] In the formula, This is the non-difference error correction value; and These are pseudorange and carrier phase observations, respectively. For satellites; For reference only; Assign frequency numbers; For receiver; The geometric distance between the satellite and the receiver; and These are the receiver and satellite clock errors, respectively, in meters (m). The tropospheric wet delay is the signal propagation path. This is the frequency-dependent ionospheric delay amplification factor; Indicates the L1 frequency tilted path ionospheric delay; For frequency The wavelength; For carrier phase ambiguity; For the hardware delay at the receiver end, Due to hardware latency at the satellite end, express and .

[0054] The reference station error correction consists of receiver error, satellite error, and atmospheric delay error. The carrier phase non-difference error correction also includes integer ambiguity in the observations. This ambiguity is transferred to the virtual observations during the VRS observation generation process, affecting only the magnitude of integer ambiguity in the virtual observations without affecting the high-precision positioning of the virtual reference station.

[0055] In short baseline RTK positioning, it is assumed that the error corrections of the reference station and the user station have good spatial correlation. Therefore, after the observations are differencing, the residual atmospheric error will not affect the fixation of the user's integer ambiguity.

[0056] Step 3: Based on the principle of spatial correlation of atmospheric errors, when generating a VRS station near a single reference station, it is assumed that the atmospheric error of the VRS station is consistent with that of the actual reference station. Using the non-difference error correction of the single reference station and the geometric distance from the VRS station to the satellite, pseudorange and carrier phase virtual observations are generated to replace the actual observations of the original reference station.

[0057] Virtual Reference Station Up to satellite No. The VRS pseudorange and carrier phase observations at a frequency can be expressed as:

[0058]

[0059]

[0060] In the formula, and These are the pseudorange and carrier non-difference error corrections for reference station A, respectively. They can be obtained directly from the observations of reference A, or by interpolating the combined error corrections of VRS from multiple surrounding reference stations. The exact coordinates of the VRS to be generated. The satellite position is obtained by iteratively using the broadcast ephemeris at the reference station observation time.

[0061] The principle of VRS observation generation is as follows: Figure 2 As shown, A represents a single reference station in the reference station network, V represents the VRS to be generated, and the circle represents the operating range of reference station A. It is assumed that the atmospheric errors of each satellite within the circle's coverage area are consistent. The generated VRS observations have the same satellite-end and receiver-end errors as the original observations. The only difference is that the VRS station maintains the same atmospheric error as the original reference station even after movement. This is the main reason for the loss of accuracy in VRS observations. Therefore, when generating a single-reference-station VRS, we need to pay attention to the baseline distance between the two. The larger the baseline distance, the greater the loss of accuracy in the observations. However, the distance required for coordinate confidentiality is sufficient.

[0062] Example

[0063] To evaluate the impact of VRS (Precise Point Positioning) replacing actual reference stations on high-precision positioning and precise orbit determination, this embodiment analyzes the performance of Precise Point Positioning (PPP), NRTK (Non-Real-Time Kinematics), and Precise Orbit Determination (POD) for generating VRS observations. When generating VRS with confidential reference station network coordinates, we ensured that the translated elevation was essentially consistent with the original reference station. Therefore, the tropospheric influence can be ignored over short distances. To achieve translations at different elevations, the ERA5 model can be used to compensate for elevation errors. The main contents are as follows:

[0064] First, the impact of reference station location offset on PPP positioning was analyzed. The reference station network distribution is as follows: Figure 3 As shown, the precision product used was the Wuhan University rapid product, and the time was the 17th day of 2023. Random offsets of 10 m to 900 m were made in the plane direction of each station. The statistical information of the offset distance of each station is shown in Table 1. The maximum offset distance was 887.75 m and the average distance was 430.32 m.

[0065] Table 1 Reference Station Location Offset Distance

[0066]

[0067] Select Figure 3 The 15 stations were solved using dynamic mode. The stations before and after the position shift were solved using PPP respectively. The differences in the RMS and convergence time of the positioning results between the two were statistically analyzed. The statistical results are shown in Table 2.

[0068] Table 2. Statistics on the impact of reference station location offset on PPP

[0069]

[0070] As shown in Table 2, the impact of different offset distances on the positioning results is not significantly different, and is generally better than 1 mm. Among them, the position offsets of the 15 stations have an impact of 0.36 / 0.15 / 0.29 mm on the RMS of the E / N / U positioning results and an impact of 12 s on the convergence time.

[0071] Plot the time series of positional differences before and after the positional shifts of the ARUC and BRST stations, as shown below. Figure 4 As shown, the left figure shows the positional difference of the ARUC station before and after the positional shift, and the right figure shows the positional difference of the BRST station before and after the positional shift. Figure 4 The deviations of the positioning results of the two stations in three directions within 24 hours remained within a very small range, with a difference of less than 4 mm.

[0072] Figure 5 , Figure 6 The RMS and convergence time deviations of some station positions before and after offset are presented. Figure 5 , Figure 6 It can be seen that the difference in positioning results before and after the position shift is very small. At the CEBR station with a shift distance of 800 m, the deviations of E, N, and U are only 0.9 mm, 0.1 mm, and 0.2 mm, respectively, and the maximum convergence time difference among the five stations is 60 s.

[0073] The above PPP solution results show that the offset of the reference station position does not affect the high-precision positioning of PPP, which also indicates that the reference station network coordinate encryption method based on single reference station VRS technology meets the requirements of PPP positioning.

[0074] Then, the impact of reference station position offset on user positioning in NRTK positioning was analyzed. The original coordinates of three reference stations were offset by different distances in the X and Y directions, with offset distances set to 100 m, 500 m, 1000 m, 2000 m, 3000 m, and 5000 m respectively. The distribution of the reference stations is as follows: Figure 7 As shown.

[0075] After obtaining the non-difference error correction value from the offset distance at different locations, user positioning is performed using different non-difference error correction values. Figure 8 The time series of user positioning deviations under different offsets are presented. Figure 8 It can be seen that different offset distances have very little impact on the user's positioning results. Even when the position offset distance reaches 5000 m, the positioning results obtained with the error correction from the original coordinates are still highly consistent.

[0076] Figure 9 The impact of different reference station offset distances on the RMS of user positioning results is presented. From Figure 9 It can be seen that as the offset distance increases, the accuracy in the E, N, and U directions increases exponentially. At an offset of 5000 m, the maximum offsets in the three directions are 4.46 mm, 8.25 mm, and 12.12 mm, respectively, which does not affect the user's high-precision positioning.

[0077] Table 3 presents the accuracy and convergence time of the network RTK in the N, E, and U directions under different position offsets.

[0078] Table 3. Changes in the location difference of user stations

[0079]

[0080] As can be seen from Table 3, the position offset has a very limited impact on the network RTK localization results. Even at 5000 m, the difference in the three directions is very small, and the convergence time is 2 s. The position offset has a very limited impact on regional augmentation localization.

[0081] The results of the user positioning calculation in NRTK above show that the offset of the reference station position does not affect the user's high-precision positioning, which also shows that the coordinate encryption method based on single reference station VRS technology meets the requirements of NRTK positioning.

[0082] Finally, the impact of reference station position offset on POD was analyzed using PANDA, a satellite navigation data processing software independently developed by Wuhan University. (Selection...) Figure 3 The GPS Galileo / BDS-3 POD experiment was conducted at 126 stations worldwide from day 17 to day 19 of 2023. Random offsets of 10m-900m were randomly assigned to each station in the horizontal direction. The initial orbit was determined using information from the broadcast ephemeris and orbital dynamics parameters. The POD results before and after the station offsets were compared and statistically analyzed. The orbit determination accuracy deviation is shown below. Figure 10 As shown. From Figure 10 It can be seen that global station offset has the greatest impact on BDS3-IGSO, but its orbital deviation remains at the millimeter level, and the impact of position offset on orbit determination is within an acceptable range. Table 4 presents the statistical results of the impact of station offset on orbit determination accuracy.

[0083] Table 4. Statistical values ​​of the impact of reference station position offset on orbit determination accuracy

[0084]

[0085] As can be seen from Table 4, the orbit determination accuracy after position deviation was in the mm range over the three days, with a greater impact on BDS3, especially the BDS3-IGSO track, which reached 9 mm in the cross direction at 2023017. However, this accuracy will not affect the basic positioning performance of BDS-3.

[0086] The above calculation results show that the reference station position offset has little impact on precise orbit determination. The reference station network coordinate densification method using single reference station VRS technology meets the requirements of POD.

[0087] Therefore, this invention employs the aforementioned reference station network coordinate encryption method based on single-reference-station VRS technology. It directly generates VRS observations near a single reference station using the spatial correlation of atmospheric errors. These observations are consistent with the error characteristics of the single reference station and can replace the actual reference station to achieve coordinate encryption of the reference station network, thereby protecting the real-time data of the reference station network. Simultaneously, VRS, replacing the actual reference station, can meet the requirements of high-precision positioning and precise orbit determination, verifying the proposed reference station network coordinate encryption method based on single-reference-station VRS technology.

[0088] Finally, it should be noted that the above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for encrypting reference station network coordinates based on single reference station VRS technology, characterized in that, The specific steps are as follows: Step 1: The reference station GNSS receiver receives the non-differential pseudorange observation data and non-differential carrier phase observation data broadcast by the GNSS satellite, and uses the GNSS satellite pseudorange observation data and carrier phase observation data to obtain the pseudorange non-differential observation equation and the carrier phase non-differential observation equation. Step 2: Based on the pseudorange non-differential observation equation and the carrier phase non-differential observation equation, obtain the non-differential error correction of the pseudorange and carrier phase observation values ​​of a single reference station in the reference station network; Step 3: Based on the principle of spatial correlation of atmospheric errors, virtual observations of pseudorange and carrier phase are generated to replace the actual reference station by using the non-difference error correction of a single reference station, the accurate coordinates of the VRS to be generated, and the satellite position.

2. The reference station network coordinate encryption method based on single reference station VRS technology according to claim 1, characterized in that, In step 1, the reference station GNSS receiver receives non-differential pseudorange observation data and non-differential carrier phase observation data broadcast by the GNSS satellite; The equation for the unequal pseudorange observations of GNSS satellites received by the reference station GNSS receiver is: The equation for the unequal carrier phase observation of GNSS satellites received by the reference station GNSS receiver is: In the formula, For satellites; For receiver; Assign frequency numbers; and These are pseudorange and carrier phase observations, respectively. The geometric distance between the satellite and the receiver; and These are the receiver and satellite clock errors, respectively, in meters (m). The tropospheric wet delay of the signal propagation path is corrected using the Saastamoinen model; This is the frequency-dependent ionospheric delay amplification factor; Indicates the L1 frequency tilted path ionospheric delay; For frequency The wavelength; For carrier phase ambiguity; For the hardware delay at the receiver end, Due to hardware latency at the satellite end, express and ; and These represent the observation noise and unmodeled error corresponding to the pseudorange and carrier phase observations, respectively. In addition, GNSS observations are also affected by error terms such as antenna phase center offset and variation, phase entanglement, relativistic effects, and tidal corrections, which have been corrected using existing accurate models.

3. The reference station network coordinate encryption method based on single reference station VRS technology according to claim 1, characterized in that, In step 2, based on the pseudorange non-differenced observation equation and the carrier phase non-differenced observation equation, the non-differenced error corrections for the pseudorange and carrier phase observations of a single reference station in the reference station network are obtained, as follows: The non-difference error corrections for the pseudorange and carrier phase observations of a single reference station A in the reference station network can be expressed as: In the formula, and These are the pseudorange and carrier non-difference error corrections for reference station A, respectively. and These are pseudorange and carrier phase observations, respectively. For satellites; For reference only; Assign frequency numbers; For receiver; The geometric distance between the satellite and the receiver; and These are the receiver and satellite clock errors, respectively, in meters (m). The tropospheric wet delay is the signal propagation path. This is the frequency-dependent ionospheric delay amplification factor; Indicates the L1 frequency tilted path ionospheric delay; For frequency The wavelength; For carrier phase ambiguity; For the hardware delay at the receiver end, Due to hardware latency at the satellite end, express and .

4. The reference station network coordinate encryption method based on single reference station VRS technology according to claim 1, characterized in that, In step 3, based on the principle of spatial correlation of atmospheric errors, pseudorange and carrier phase virtual observations are generated to replace the actual reference station using the non-difference error correction of a single reference station, the accurate coordinates of the VRS to be generated, and the satellite position. Specifically, this includes: Based on the principle of spatial correlation of atmospheric errors, when generating a single VRS, it is assumed that the atmospheric errors of the actual reference station and the VRS to be generated are consistent. Using the non-difference error correction of the single reference station, and combining it with the geometric distance from the VRS to the satellite, pseudorange and carrier phase virtual observations are generated to replace the original actual observations from the reference station. The virtual reference station... Up to satellite No. The VRS pseudorange and carrier phase observations at a frequency can be expressed as: In the formula, and These are the pseudorange and carrier non-difference error corrections for reference station A, respectively. They can be obtained directly from the observations of reference A, or by interpolating the combined error corrections of VRS from multiple surrounding reference stations. The exact coordinates of the VRS to be generated. The satellite position is obtained by iteratively using the broadcast ephemeris at the reference station observation time.

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