Method and System for Ambiguity Resolution between Reference Stations of Full-Constellation Beidou Hybrid Signals

Abstract

The present invention discloses a method and system for ambiguity resolution between reference stations of the full constellation Beidou hybrid signal. The present invention first performs independent ambiguity resolution on the dual-frequency and triple-frequency signals of Beidou-2 and Beidou-3 to ensure reliable ambiguity information is obtained at different frequency bands. Subsequently, through the effective combination and analysis of these ambiguity results, unified resolution between the two is achieved. This method of separate resolution and subsequent fusion not only optimizes the utilization efficiency of the signals but also significantly improves the accuracy of ambiguity resolution. The resolution strategy proposed by the present invention not only enhances the overall performance and reliability of the positioning system but also effectively improves the accuracy of network RTK positioning. The present invention provides strong support for the practical application of the Beidou ground-based augmentation system, has important technical value, wide applicability, and good market prospects. By optimizing the joint use of satellite signals, the present invention lays a solid foundation for the development of future satellite navigation technology.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite navigation, and more particularly to a method for ambiguity resolution between reference stations in the Beidou satellite navigation system, and more specifically to a method and system for ambiguity resolution between reference stations of the full constellation Beidou hybrid signal. Background Art

[0002] With the development of the global satellite navigation system, the Beidou satellite navigation system has gradually become an important positioning service platform. The Beidou-2 and Beidou-3 satellite systems provide users with rich positioning information through different frequencies and signal characteristics. The Beidou-2 system has a wide range of applications in the Asia-Pacific region, while the global networking ability of the Beidou-3 system further enhances the positioning accuracy.

[0003] There are relatively many research results on the joint data processing methods corresponding to Beidou-2 and Beidou-3. Tang Weiming et al. proposed the IF TCAR reference station ambiguity determination method. For the ambiguity resolution of the Beidou-2 triple-frequency long-distance reference station network, this method uses the known position of the reference station, the easily resolved extra-wide lane (EWL) ambiguity, and the IF phase combination to reliably fix the WL ambiguity, and basically achieves 100% reliable ambiguity fixation. For details, please refer to the literature: Tang W, Shen M, Deng C, etal. 2018. Network-based triple-frequency carrier phase ambiguity resolutionbetween reference stations using BDS data for long baselines [J]. GPSSolutions, 22 (3): 73. Deng Chenlong et al. proposed a method for joint solution of Beidou-2 and Beidou-3 for short-distance RTK positioning. This method determines the extra-wide lane and wide lane ambiguities of BDS-2 and BDS-3 respectively by means of intra-system differencing, and then constructs an error equation set using the wide lane observation values and the original observation values composed of B1I and B3I to solve the original ambiguity, and finally realizes the integrated positioning of BDS-2 and BDS-3. For details, please refer to the literature: Deng C, Qi S, Tang W, et al. 2022.Model comparison and performance analysis of multi-frequency precisepositioning with the joint BDS-2 and BDS-3 system [J]. Advances in SpaceResearch, 69 (8): 3044-3058. In RTK terminal positioning, the loose combination method or the tight combination method can be adopted for BDS2 and BDS3. However, on the server side, in order to ensure the consistency of the correction data, it is necessary to unify the reference of the correction data of BDS2 and BDS3. Otherwise, the terminal can only adopt the loose combination method for solution.

[0004] However, due to the frequency differences between Beidou-2 and Beidou-3 satellites, there are certain challenges in jointly resolving the ambiguities of the two. Traditional ambiguity resolution methods mostly target a single satellite system and it is difficult to make full use of the advantages of the joint system. In practical applications, how to effectively integrate the multi-frequency signals of Beidou-2 and Beidou-3 to achieve efficient and accurate ambiguity resolution has become the key to improving the quality of network RTK (real-time kinematic positioning) services.

[0005] Current research mainly focuses on signal processing and ambiguity fixing techniques, but there are still problems such as low signal utilization efficiency and insufficient solution accuracy in practical applications. Therefore, there is an urgent need for a new solution method to effectively integrate the signals of Beidou-2 and Beidou-3 satellites and improve the overall performance and reliability of the positioning system. Summary of the Invention

[0006] The present invention provides a method for ambiguity resolution between reference stations of the Beidou-2 and Beidou-3 satellite combined with the Beidou ground-based augmentation system, aiming to improve the positioning accuracy and reliability of the satellite navigation system. The core of this method lies in making full use of the advantages of the three-frequency signals of Beidou-2 and Beidou-3 respectively, and adopting an innovative solution strategy of "separate first and then fuse", which specifically includes the following steps:

[0007] Step 1: Based on the MW combination rounding method, respectively determine the ultra-wide lane ambiguities of the Beidou-2 and Beidou-3 systems.

[0008] Step 2: Based on the TCAR method of the ionosphere-free combination, respectively determine the fixed values of the wide lane ambiguities of the Beidou-2 and Beidou-3 systems.

[0009] Step 3: Use the double-difference wide lane ambiguity determination method to obtain the wide lane ambiguities of the Beidou-2 and Beidou-3 combined system.

[0010] Step 4: Through transformation, obtain the fixed solution of the wide lane ambiguities of the Beidou-2 and Beidou-3 combined system for the unified reference satellite.

[0011] Step 5: For the Beidou-2 and Beidou-3 combined system of the unified reference satellite, based on the Kalman filter, determine the ionosphere-free combination ambiguities of the double-difference B1I and B3I frequencies, and then combine with the fixed solution of the wide lane ambiguity to determine the original ambiguities of B1I of all satellites; where B1I and B3I are different frequency signals in Beidou-2 and Beidou-3 satellites.

[0012] Furthermore, the specific implementation in Step 1 includes the following sub-steps:

[0013] Step 1.1: Form the double-difference pseudorange and phase observations of the Beidou-2 and Beidou-3 systems between reference stations.

[0014] Respectively select the satellite with the highest elevation angle among Beidou-2 satellites and the satellite with the highest elevation angle among Beidou-3 satellites as the reference satellites of their respective systems, and obtain the non-combined pseudorange observations and phase observations of their respective systems through double-difference operations; where, is the double-difference operator between different reference stations and between non-reference satellites and reference satellites. The subscripts 1, 2, and 3 represent three different signal frequencies respectively;

[0015] Step 1.2: Calculate the double-difference pseudorange combined virtual observation value according to the double-difference pseudorange and phase observation values in Step 1.1 and the phase combined observation value ;

[0016]

[0017]

[0018] where , c is the speed of light, and are constants;

[0019] Step 1.3: Calculate the ultra-wide-lane ambiguities of the Beidou-2 and Beidou-3 systems respectively. The formula is as follows:

[0020]

[0021] In the formula, is the rounding integer operator.

[0022] Furthermore, in Step 2, use the ionosphere-free combined virtual observation value, double-difference satellite-to-ground distance, and tropospheric delay to calculate the ionosphere-free combined float ambiguity, and obtain the fixed value of the wide-lane ambiguity through multi-epoch smoothing. The specific implementation method is as follows:

[0023] Step 2.1: Use the double-difference phase observation values in Step 1.1 to form two ionosphere-free combined observation values:

[0024]

[0025] In the formula, , and are constants;

[0026] Step 2.2: According to the accurately known coordinates of the reference station and the calculated satellite positions, determine the geometric distances between each satellite and the reference station. In the formula, is the reference station receiver coordinate, is the satellite coordinate. Then, according to the double-difference operator obtain the double-difference satellite-to-ground distance ;

[0027] Step 2.3: Use the Hopfield model to calculate the zenith tropospheric hydrostatic delay ZHD and wet delay ZWD of each reference station, and then use the Niell projection function to calculate the projection function values of the hydrostatic delay and wet delay of each satellite, so as to obtain the tropospheric delay of each satellite on the slant path. According to the double-difference operator, obtain the double-difference tropospheric delay; MF H and the projection function values of the wet delay MF W to obtain the tropospheric delay of each satellite on the slant path ; according to the double-difference operator obtain the double-difference tropospheric delay ;

[0028] Step 2.4: According to the ionosphere-free combination observations in Step 2.1 and , the double-difference satellite-to-ground range in Step 2.2 , and the double-difference tropospheric delay in Step 2.3 , calculate the float ambiguity of the corresponding ionosphere-free combination. The formula is as follows:

[0029]

[0030] where , is the wavelength of the corresponding ionosphere-free combination;

[0031] Step 2.5: Use the float ambiguity of the ionosphere-free combination in Step 2.4 and the ultra-wide-lane ambiguity in Step 1 to calculate the float wide-lane ambiguity of Beidou-2 and Beidou-3 respectively :

[0032]

[0033] where

[0034]

[0035] Step 2.6: Smooth the float wide-lane ambiguity obtained in Step 2.5 over multiple epochs, and round it to obtain the fixed value of the wide-lane ambiguity. The formula is as follows:

[0036]

[0037] where k is the number of epochs, is the rounding operator. Denote the fixed values of the wide-lane ambiguity of the Beidou-2 system and the Beidou-3 system as , .

[0038] Further, in step 3, taking the Beidou-3 satellite as the reference satellite, the pseudorange and phase observations of the double-difference B1I and B3I frequencies of the combined Beidou-2 and Beidou-3 systems between the reference stations are formed. Using the ionosphere-free combined pseudorange and phase observations, the initial value and fixed solution of the wide-lane ambiguity are determined, which specifically includes the following sub-steps:

[0039] Step 3.1, taking the Beidou-3 satellite as the reference satellite, forming the pseudorange observations of the double-difference B1I and B3I frequencies of the combined Beidou-2 and Beidou-3 systems between two reference stations and 、phase observations and ;

[0040] Step 3.2, according to the double-difference pseudorange and phase observations in step 3.1, calculating the initial value of the wide-lane ambiguity of the combined Beidou-2 and Beidou-3 systems;

[0041] Step 3.3, according to the double-difference phase observations in step 3.1, obtaining the ionosphere-free combined pseudorange and phase observations of the double-difference B1I and B3I frequencies, and then calculating the initial value of the wide-lane ambiguity of the combined Beidou-2 and Beidou-3 systems;

[0042] Step 3.4, calculating the double-difference satellite-to-ground distance and double-difference tropospheric delay of all satellites of the combined system with;

[0043] Step 3.5, according to the ionosphere-free combined pseudorange and phase observations in step 3.3, determining the first form of the ionosphere-free combined ambiguity:

[0044]

[0045] According to the double-difference satellite-to-ground distance and double-difference tropospheric delay obtained in step 3.4, determining the second form of the ionosphere-free combined ambiguity:

[0046]

[0047] is the wavelength of the ionosphere-free combination. Comparing the two forms of the ionosphere-free combined ambiguity, obtaining the difference between the two forms of the ionosphere-free combined ambiguity at this moment, and successively calculating the standard deviation before rounding of the initial value of the wide-lane ambiguity in step 3.2;

[0048] Step 3.6, with the initial value of the wide-lane ambiguity obtained in step 3.2 as the center, with Using the search radius, search for the wide-lane ambiguity and calculate the residuals corresponding to different wide-lane ambiguities. If the residual value is less than half of the wide-lane combined wavelength, the corresponding wide-lane ambiguity is considered fixed.

[0049] Step 3.7: Calculate the wide-lane ambiguity by back-calculating the geometric distance and compare it with the wide-lane ambiguity determined in Step 3.6. If the two are consistent, the corresponding wide-lane ambiguity is considered to be correctly fixed.

[0050] Furthermore, in Step 3.2, calculate the initial value of the wide-lane ambiguity of the Beidou-2 and Beidou-3 combined system. The calculation formula is as follows:

[0051]

[0052] where the wide-lane combined wavelength , the pseudo-range combination , the phase combination ; , and are constants, c is the speed of light, is the rounding integer operator.

[0053] Furthermore, in Step 3.3, obtain the ionosphere-free combined pseudo-range and the phase observation of the double-difference B1I and B3I frequencies. The calculation formula is as follows:

[0054]

[0055]

[0056] where , and are constants.

[0057] Furthermore, in Step 3.5, first calculate the difference between the two forms of ionosphere-free combined ambiguities, and then use the differences k of the first epochs to statistically calculate its root mean square . The calculation formula is:

[0058]

[0059] When the root mean square converges, that is, and , N is a constant. is a positive decimal less than 1 and will not be updated , and denote the converged as , which is the standard deviation of the ionosphere-free combined ambiguity;

[0060] Ignore the phase observation noise and assume that the double-difference pseudorange noise of B1I is 5 times that of B3I, that is . According to the standard deviation of the ionosphere-free combined ambiguity, calculate the double-difference pseudorange noise :

[0061]

[0062] In the formula, ; then calculate the standard deviation of the wide-lane ambiguity initial value before rounding in step 3.2:

[0063]

[0064] In the formula, , , and are constants.

[0065] Furthermore, in step 4, the wide-lane ambiguity of the BDS-2 and BDS-3 joint system with a unified reference satellite is obtained through transformation, where the wide-lane ambiguity fixed value of the BDS-3 satellite is directly used ; specifically, it includes the following sub-steps:

[0066] Step 4.1, among the satellite pairs with the wide-lane ambiguity correctly fixed in step 3, select a BDS-2 satellite , and this satellite needs to meet the following 2 conditions: (1) needs to be the satellite participating in the solution in step 2, whether it is a reference satellite or not ; (2) 's elevation angle and azimuth angle are the closest to the reference satellite , and the wide-lane ambiguity of the selected satellite pair is denoted as ;

[0067] Step 4.2, transform the wide-lane ambiguity fixed value of BDS-2 obtained in step 2 to obtain the wide-lane ambiguity fixed value with as the reference satellite; specifically:

[0068] If , then the wide-lane ambiguity fixed value of the non-reference BDS-2 satellite relative to in step 2 is , and the BDS-2 reference satellite relative to The fixed value of the wide-lane ambiguity is ;

[0069] If , first find out the Beidou-2 non-reference satellites obtained by calculation in step 2 relative to the reference satellite of the fixed value of the wide-lane ambiguity , then the fixed value of the wide-lane ambiguity of the remaining Beidou-2 non-reference satellites relative to is , and the fixed value of the wide-lane ambiguity of the Beidou-2 non-reference satellite relative to is ; the fixed value of the wide-lane ambiguity of the Beidou-2 reference satellite relative to is .

[0070] Furthermore, in step 5, the ionosphere-free combined floating ambiguity is determined by using Kalman filtering, and combined with the wide-lane ambiguity, the B1I raw ambiguity of all satellites is finally determined; specifically, it includes the following sub-steps:

[0071] Step 5.1, using the ionosphere-free combined phase observations formed in step 3.3 , the double-differenced satellite-to-ground range obtained in step 3.4 and the double-differenced tropospheric delay , form the ionosphere-free combined phase observation equation of the Beidou-2 and Beidou-3 joint system with as the reference satellite:

[0072]

[0073] Determine the ionosphere-free combined floating ambiguity through Kalman filtering;

[0074] Step 5.2, using the wide-lane ambiguity of the Beidou-2 satellites and Beidou-3 satellites relative to obtained in step 4, and combining with the ionosphere-free combined ambiguity determined in step 5.3, determine the B1I raw ambiguity of all satellites:

[0075]

[0076] , and are constants;

[0077] Step 5.3, smooth the B1I floating ambiguity obtained in step 5.2 through multi-epoch smoothing, the fixed value of the ambiguity is obtained by rounding, and the formula is as follows:

[0078]

[0079] is the rounding operator, and k is the epoch number.

[0080] Through the above steps, the method of the present invention realizes the effective integration of Beidou-2 and Beidou-3 satellite signals, improves the accuracy of network RTK positioning and the overall performance of the system, and has important technical value and broad application prospects.

[0081] The present invention also provides an ambiguity resolution system between reference stations for the full constellation Beidou hybrid signal, including:

[0082] A processor and a memory. The memory is used to store program instructions, and the processor is used to call the stored instructions in the memory to execute the method described in the above technical solution.

[0083] The beneficial effects produced by the present invention are:

[0084] 1. By adopting the resolution strategy of "separate first and then fuse", the present invention makes full use of the advantages of the three-frequency signals of Beidou-2 and Beidou-3 respectively, improves the signal utilization efficiency, enables the system to perform effective positioning under a wider range of conditions, effectively eliminates the problem of inconsistent ambiguity caused by signal frequency differences, enhances the reliability of the system, and ensures the stability of positioning services.

[0085] 2. The present invention provides an innovative technical solution for the practical application of the Beidou ground-based augmentation system, especially for the ambiguity resolution of the joint use of Beidou-2 and Beidou-3 satellites to improve positioning accuracy and system reliability. The present invention promotes the further development of satellite navigation technology and has important technical value and market potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 is the flowchart of the method of the embodiment of the present invention.

[0087] Figure 2 is the method diagram for selecting the optimal Beidou-2 satellite of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0088] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0089] The present invention provides a method for ambiguity resolution between reference stations of the Beidou-2 and Beidou-3 satellite combined with the Beidou ground-based augmentation system. Based on the rounding method of the MW combination (Melbourne-Wubeena combination, the MW combination is a combined observation value algorithm proposed by Melbourne and Wubbena), the ultra-wide lane ambiguities of Beidou-2 and Beidou-3 are determined respectively (step 1); based on the TCAR method (Three carrier ambiguity resolution) of the ionosphere-free combination, the fixed values of the wide lane ambiguities of Beidou-2 and Beidou-3 are determined respectively (step 2); the dual-frequency (B1I, B3I) wide lane ambiguity of the combination of Beidou-2 and Beidou-3 is determined (step 3); the optimal Beidou-3 satellite is selected as the reference satellite to unify the wide lane ambiguities of Beidou-2 and Beidou-3 (step 4); based on the Kalman filter, the ionosphere-free combination ambiguity of the B1I and B3I signals is determined, and then combined with the fixed value of the wide lane ambiguity to finally determine the original ambiguity of B1I of all satellites (step 5). See Figure 1 and Figure 2 , a method for ambiguity resolution between reference stations of the Beidou-2 and Beidou-3 satellite combined with the Beidou ground-based augmentation system provided in the embodiment of the present invention specifically includes the following steps:

[0090] Step 1, based on the rounding method of the MW combination, determine the ultra-wide lane ambiguities of Beidou-2 and Beidou-3 respectively.

[0091] Step 1.1, form the double-differenced pseudorange and phase observations of the Beidou-2 and Beidou-3 systems between reference stations.

[0092] Select the satellite with the highest elevation angle among Beidou-2 satellites and the satellite with the highest elevation angle among Beidou-3 satellites as the reference satellites of their respective systems, and obtain the non-combined pseudorange observations and phase observations of their respective systems through double-differencing operations. In the formula, is the double-differencing operator between different reference stations and between non-reference satellites and reference satellites. The subscripts 1, 2, and 3 respectively represent three different signal frequencies. For Beidou-2 satellites, they are B1I, B2I, and B3I frequency signals respectively; for Beidou-3, they are B1I, B2a, and B3I frequency signals respectively.

[0093] Step 1.2, according to the double-differenced pseudorange and phase observations in step 1.1, calculate the double-differenced pseudorange combined observation value and the phase combined observation value :

[0094]

[0095]

[0096] where , c is the speed of light. , and for the Beidou-2 system, ; for the Beidou-3 system, .

[0097] Step 1.3, calculate the ultra-wide lane ambiguities of the Beidou-2 and Beidou-3 systems respectively , and the formula is as follows:

[0098]

[0099] In the formula, is the rounding integer operator.

[0100] Step 2: Based on the TCAR method of the ionosphere-free combination, determine the fixed values of the wide lane ambiguities of the Beidou-2 and Beidou-3 systems respectively.

[0101] Step 2.1, use the double-difference phase observations in Step 1.1 to form two ionosphere-free combination observations:

[0102]

[0103] In the formula, for both the Beidou-2 and Beidou-3 systems, there is .

[0104] Step 2.2, according to the accurately known coordinates of the reference station and the calculated satellite positions, determine the geometric distances between each satellite and the reference station , where in the formula is the receiver coordinate of the reference station, is the satellite coordinate. Then, according to the double-difference operator obtain the double-difference ground-satellite distance .

[0105] Step 2.3, use the Hopfield model to calculate the zenith tropospheric hydrostatic delay ZHD and wet delay ZWD of each reference station, and then use the Niell projection function to calculate the projection function values of the hydrostatic delay MF H and the projection function values of the wet delay MF W to obtain the tropospheric delay of each satellite on the slant path . According to the double-difference operator obtain the double-difference tropospheric delay .

[0106] Step 2.4, according to the ionosphere-free combination observations in Step 2.1 and and the double-differenced satellite-to-satellite range in Step 2.2 and the double-differenced tropospheric delay in Step 2.3 , calculate the floating ambiguities corresponding to the ionosphere-free combination, with the formula as follows:

[0107]

[0108] In the formula , is the wavelength corresponding to the ionosphere-free combination.

[0109] Step 2.5: Using the ionosphere-free combination floating ambiguities in Step 2.4 and the ultra-wide-lane ambiguities in Step 1, calculate the floating wide-lane ambiguities of BDS-2 and BDS-3 respectively .

[0110]

[0111] In the formula,

[0112]

[0113] Step 2.6: Smooth the floating wide-lane ambiguities obtained in Step 2.5 over multiple epochs and round to obtain the fixed values of the wide-lane ambiguities , with the formula as follows:

[0114]

[0115] In the formula, k is the number of epochs. Denote the fixed values of the wide-lane ambiguities of the BDS-2 system and the BDS-3 system as 、 .

[0116] Step 3: Using the method for determining double-differenced wide-lane ambiguities in the three-step method, obtain the wide-lane ambiguities of the combined BDS-2 and BDS-3 system

[0117] Step 3.1: Taking the BDS-3 satellite as the reference satellite, form the pseudo-range observations and of the double-differenced B1I and B3I frequencies of the combined BDS-2 and BDS-3 system between two reference stations and .

[0118] Step 3.2: According to the double-differenced pseudo-range and phase observations in Step 3.1, calculate the initial values of the wide-lane ambiguities of the combined BDS-2 and BDS-3 system:

[0119]

[0120] Among them, the wide-lane combined wavelength , the pseudorange combination , the phase combination

[0121] Step 3.3: According to the double-difference phase observations in Step 3.1, obtain the ionosphere-free combined pseudorange and phase observations of the double-difference B1I and B3I frequencies:

[0122]

[0123]

[0124] Step 3.4: Similar to Steps 2.2 and 2.3, re-obtain the double-difference satellite-to-ground distances of all satellites in the combined system with as the reference satellite and the double-difference tropospheric delay .

[0125] Step 3.5: According to the ionosphere-free combined pseudorange and phase observations in Step 3.3, determine the first form of the ionosphere-free combined ambiguity:

[0126]

[0127] According to the double-difference satellite-to-ground distances and the double-difference tropospheric delay obtained in Step 3.4, determine the second form of the ionosphere-free combined ambiguity:

[0128]

[0129] Compare the two forms of the ionosphere-free combined ambiguity to obtain the difference of the two forms of the ionosphere-free combined ambiguity at this moment. Then use the differences k of the previous epochs to statistically calculate its root mean square , and the calculation formula is:

[0130]

[0131] When the root mean square converges, that is and ( N can take 50 or 100, is a positive decimal less than 1 and can take 0.5), stop updating , and record the converged as , which is the standard deviation of the ionosphere-free combined ambiguity.

[0132] Ignore the phase observation noise and assume that the double-difference pseudorange noise of B1I is 5 times that of B3I, i.e., , the double-difference pseudorange noise can be calculated according to the standard deviation of the ionosphere-free combination ambiguity : :

[0133]

[0134] In the formula, . Then calculate the standard deviation of the wide-lane ambiguity before rounding in step 3.2:

[0135]

[0136] In the formula, .

[0137] Step 3.6: Centered on the initial value of the wide-lane ambiguity obtained in step 3.2, with as the search radius, search for the wide-lane ambiguity. Calculate the residuals corresponding to different wide-lane ambiguities :

[0138]

[0139] If the residual value is less than half of the wide-lane combination wavelength , it is considered that the corresponding wide-lane ambiguity has been fixed.

[0140] Step 3.7: Use the geometric distance to back-calculate the wide-lane ambiguity:

[0141]

[0142] And compare it with the wide-lane ambiguity determined in step 3.6. If they are consistent, it is considered that the corresponding wide-lane ambiguity has been correctly fixed.

[0143] Step 4: Obtain the fixed solution of the wide-lane ambiguity of the combined BDS-2 and BDS-3 systems with a unified reference satellite through transformation. Among them, the BDS-3 satellites directly use the fixed value of the wide-lane ambiguity obtained in step 2 .

[0144] Step 4.1: Among the satellite pairs with the wide-lane ambiguity correctly fixed in step 3, select a BDS-2 satellite , which needs to meet the following 2 conditions: (1) needs to be a satellite participating in the solution in step 2, whether it is a reference satellite or not ; (2) 's elevation angle and azimuth angle are the closest to those of the reference satellite . The wide-lane ambiguity of the selected satellite pair is denoted as .

[0145] Step 4.2: Transform the fixed value of the BDS-2 wide-lane ambiguity obtained in Step 2 to obtain the fixed value of the wide-lane ambiguity with as the reference satellite. Specifically:

[0146] If , then the fixed value of the wide-lane ambiguity of the BDS-2 non-reference satellite relative to in Step 2 is , and the fixed value of the wide-lane ambiguity of the BDS-2 reference satellite relative to is ;

[0147] If , first find out the fixed value of the wide-lane ambiguity of the BDS-2 non-reference satellite calculated in Step 2 relative to the reference satellite which is , then the fixed value of the wide-lane ambiguity of the remaining BDS-2 non-reference satellites relative to is , and the fixed value of the wide-lane ambiguity of the BDS-2 non-reference satellite relative to is ; the fixed value of the wide-lane ambiguity of the BDS-2 reference satellite relative to is .

[0148] Step 5: Determine the initial ambiguities of B1I for all satellites in the combined BDS-2 and BDS-3 system with as the reference satellite.

[0149] Step 5.1: Use the ionosphere-free combined phase observations formed in Step 3.3, the double-differenced satellite-to-ground range obtained in Step 3.4, and the double-differenced tropospheric delay to form the ionosphere-free combined phase observation equation for the combined BDS-2 and BDS-3 system with as the reference satellite:

[0150]

[0151] Determine the ionosphere-free combined floating ambiguities through Kalman filtering;

[0152] Step 5.2: Use the wide-lane ambiguities of the BDS-2 satellites and BDS-3 satellites relative to obtained in Step 4, and combine with the ionosphere-free combined ambiguities , determine the B1I raw ambiguity of all satellites:

[0153]

[0154] Step 5.3, similar to Step 2.6, smooth the B1I floating-point ambiguity obtained in Step 5.2 through multi-epoch , round it to obtain the fixed value of the ambiguity, and the formula is as follows:

[0155]

[0156] In specific implementation, the above process can be automatically run by computer software technology, and the system device for running the method process of the present invention should also be within the protection scope of the present invention.

[0157] On the other hand, the embodiment of the present invention also provides an inter-base-station ambiguity resolution system for the full constellation Beidou hybrid signal, including:

[0158] A processor and a memory, the memory is used to store program instructions, and the processor is used to call the stored instructions in the memory to execute the method described in the above technical solution.

[0159] The specific embodiments described herein are only illustrative of the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for resolving ambiguity between reference stations of a full-constellation Beidou hybrid signal, characterized in that: The following steps are involved: Step 1: Based on the MW combination rounding method, the ultra-wide lane ambiguity of the BeiDou-2 and BeiDou-3 systems are determined respectively; Step 2: Based on the ionosphere-free combined TCAR method, the wide lane ambiguity fixed values ​​of the BeiDou-2 and BeiDou-3 systems are determined respectively; Step 3, using the double-difference wide lane ambiguity determination method to obtain the wide lane ambiguity of the BeiDou-2 and BeiDou-3 joint system; Step 4, obtain the wide lane ambiguity fixed solution of the BeiDou-2 and BeiDou-3 joint system of the unified reference satellite through transformation; Step 5, for the BeiDou-2 and BeiDou-3 joint system with a unified reference satellite, the ionospheric-free combined ambiguity of the double difference B1I and B3I frequencies is determined based on Kalman filtering, and then combined with the wide lane ambiguity fixed solution to determine the original ambiguity of B1I of all satellites; where B1I and B3I are different frequency signals in BeiDou-2 and BeiDou-3 satellites.

2. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 1, characterized in that: The specific implementation of step 1 includes the following sub-steps: Step 1.1, establish the double-difference pseudo-range and phase observation values ​​of the BeiDou-2 and BeiDou-3 systems between the reference stations; Select the satellite with the highest elevation angle among the BeiDou-2 satellites The satellite with the highest altitude angle among the BeiDou-3 satellites As the reference satellite of each system, the non-combined pseudo-range observation values ​​of each system are obtained through double difference operation and phase observations ; In the formula, It is the double difference operator between different reference stations and between non-reference satellites and reference satellites. The subscripts 1, 2, and 3 represent three different signal frequencies respectively; Step 1.2, based on the double-difference pseudo-range and phase observation values ​​of step 1.1, calculate the double-difference pseudo-range combined virtual observation value And phase combination observations ; in , c is the speed of light, and is a constant; Step 1.3, calculate the ultra-wide lane ambiguity of the BeiDou-2 and BeiDou-3 systems respectively, the formula is as follows: In the formula, The rounding operator.

3. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 2, characterized in that: In step 2, the ionosphere-free combined virtual observations, double differential ground-to-satellite distances and tropospheric delays are used to calculate the ionosphere-free combined floating-point ambiguity, and the fixed value of the wide-lane ambiguity is obtained by multi-epoch smoothing; the specific implementation method is as follows: Step 2.1, using the double difference phase observations from step 1.1, construct two ionosphere-free combined observations: In the formula, , and is a constant; Step 2.2: Determine the geometric distance between each satellite and the reference station based on the precisely known coordinates of the reference station and the calculated satellite positions. , where is the base station receiver coordinate, is the satellite coordinate, and then according to the double difference operator Get double differential ground distance ; Step 2.3: Use the Hopfield model to calculate the zenith tropospheric static delay ZHD and wet delay ZWD of each reference station, and then use the Niell projection function to calculate the projection function value of the static delay of each satellite. MF H and the projection function value of wet delay MF W , get the tropospheric delay of each satellite on the slant path , according to the double difference operator Get the double difference tropospheric delay ; Step 2.4, based on the ionosphere-free combined observations from step 2.1 and , double differential ground-to-ground distance in step 2.2 , double difference tropospheric delay in step 2.3 , calculate the floating point ambiguity corresponding to the ionosphere-free combination, the formula is as follows: In the formula , is the wavelength corresponding to the ionosphere-free combination; Step 2.5, using the ionospheric-free combined floating ambiguity of step 2.4 and the ultra-wide lane ambiguity of step 1, calculate the floating wide lane ambiguity of BeiDou-2 and BeiDou-3 respectively : In the formula, Step 2.6, multi-epoch smoothing of the floating point wide lane ambiguity obtained in step 2.5, rounding to obtain a fixed value of the wide lane ambiguity, the formula is as follows: In the formula, k is the epoch number, is the rounding operator, and the fixed values ​​of wide lane ambiguity of BeiDou-2 system and BeiDou-3 system are , .

4. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 1, characterized in that: In step 3, the BeiDou-3 satellite is used as the reference satellite to form the pseudorange and phase observations of the double-difference B1I and B3I frequencies of the BeiDou-2 and BeiDou-3 joint system between the reference stations. The initial value and fixed solution of the wide lane ambiguity are determined by using the ionosphere-free combined pseudorange and phase observations, which specifically includes the following substeps: Step 3.1, BeiDou-3 satellite For reference satellites, pseudo-range observation values ​​of double difference B1I and B3I frequencies of BeiDou-2 and BeiDou-3 joint system are established between two reference stations and , phase observation value and ; Step 3.2, based on the double-difference pseudorange and phase observation values ​​in step 3.1, calculate the initial value of the wide-lane ambiguity of the BeiDou-2 and BeiDou-3 joint system; Step 3.3, based on the double difference phase observations in step 3.1, obtain the ionospheric-free combined pseudorange of the double difference B1I and B3I frequencies and phase observations , and then calculate the initial value of the wide-lane ambiguity of the BeiDou-2 and BeiDou-3 joint system; Step 3.4, calculate The double differential Earth-satellite distance of all satellites in the joint system is the reference satellite and double-difference tropospheric delay ; Step 3.5, based on the ionospheric-free combined pseudorange and phase observations of step 3.3, determine the first form of the ionospheric-free combined ambiguity: According to the double differential ground-to-ground distance obtained in step 3.4 and double-difference tropospheric delay , determine the second form of the ionospheric-free combined ambiguity: The wavelength of the ionosphere-free combination is compared with the two forms of ionosphere-free combination ambiguity to obtain the difference between the two forms of ionosphere-free combination ambiguity at this moment, and the standard deviation of the wide lane ambiguity before rounding the initial value in step 3.2 is calculated in turn. ; Step 3.6, taking the initial value of wide lane ambiguity obtained in step 3.2 as the center, is the search radius, and the wide lane ambiguity is searched. Different wide lane ambiguities are calculated. The corresponding residual; if the residual value is less than the wide lane combination wavelength half of , the corresponding wide-lane ambiguity is considered to be fixed; In step 3.7, the wide lane ambiguity is obtained by back-calculating the geometric distance and compared with the wide lane ambiguity determined in step 3.

6. If the two are consistent, it is considered that the corresponding wide lane ambiguity has been correctly fixed.

5. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 4, characterized in that: In step 3.2, the initial value of the wide-lane ambiguity of the BeiDou-2 and BeiDou-3 joint system is calculated using the following formula: The wavelength of the wide lane combination , pseudorange combination , phase combination ; , and is a constant, c is the speed of light, The rounding operator.

6. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 4, characterized in that: In step 3.3, the ionospheric-free combined pseudorange of the double difference B1I and B3I frequencies is obtained and phase observations , the calculation formula is as follows: in, , and is a constant.

7. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 4, characterized in that: In step 3.5, the difference between the two forms of ionospheric-free combined ambiguity is first calculated , and then use the previous k The difference of epochs , by calculating the root mean square of multiple epochs , the calculation formula is: When the RMS Convergence, that is and hour, N is a constant, If it is a positive decimal less than 1, it will not be updated. , after convergence for , is the standard deviation of the ionospheric-free combined ambiguity; Ignore the phase observation noise, and assume that the double-difference pseudorange noise of B1I is 5 times that of B3I, that is, , according to the standard deviation of the ionospheric-free combined ambiguity Calculate double difference pseudorange noise : In the formula, ; Then calculate the standard deviation of the wide lane ambiguity before rounding the initial value in step 3.2 : In the formula, , , and is a constant.

8. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 1, characterized in that: In step 4, the wide lane ambiguity of the BeiDou-2 and BeiDou-3 joint system of the unified reference satellite is obtained by transformation, among which the BeiDou-3 satellite directly adopts the wide lane ambiguity fixed value ; Specifically includes the following sub-steps: Step 4.1: Select a BeiDou-2 satellite from the satellite pair whose wide-lane ambiguity is correctly fixed in step 3. , the satellite must meet the following two conditions: (1) The satellite involved in the solution in step 2 must be a reference satellite or not. ; (2) The altitude and azimuth of the reference satellite The widelane ambiguity of the closest selected satellite pair is denoted by ; Step 4.2, transform the BeiDou-2 wide lane ambiguity fixed value obtained in step 2 to obtain is the fixed value of the wide lane ambiguity of the reference satellite; specifically: like , then the BeiDou-2 non-reference satellite in step 2 is relative to The wide lane ambiguity is fixed at , BeiDou-2 reference satellite relatively The wide lane ambiguity is fixed at ; like , first find the BeiDou-2 non-reference satellite calculated in step 2 Relative reference satellite The wide lane ambiguity fixed value , then the remaining non-reference satellites of BeiDou-2 are relative The wide lane ambiguity is fixed at , BeiDou-2 non-reference satellite relatively The wide lane ambiguity is fixed at ; BeiDou-2 reference satellite relatively The wide lane ambiguity is fixed at .

9. The method for resolving ambiguity between reference stations of the full-constellation Beidou hybrid signal according to claim 1, characterized in that: In step 5, the Kalman filter is used to determine the ionospheric-free combined floating point ambiguity, and combined with the wide lane ambiguity, the B1I raw ambiguity of all satellites is finally determined; specifically, the following sub-steps are included: Step 5.1, using the ionospheric-free combined phase observations constructed in step 3.3 , the double differential ground-to-ground distance obtained in step 3.4 and double-difference tropospheric delay , formed with The ionospheric-free combined phase observation equation of the BeiDou-2 and BeiDou-3 joint system is: Determine the ionospheric-free combined floating point ambiguity through Kalman filtering ; Step 5.2: Use the relative position of BeiDou-2 satellite and BeiDou-3 satellite obtained in step 4 Wide Lane Ambiguity , combined with the ionospheric-free combined ambiguity determined in step 5.3 , determine the B1I raw ambiguities of all satellites: , and is a constant; Step 5.3, smoothing the B1I floating point ambiguity obtained in step 5.2 over multiple epochs , rounded to get a fixed value of fuzziness, the formula is as follows: is the rounding operator and k is the number of epochs.

10. The inter-reference station ambiguity resolution system for the full constellation Beidou hybrid signal is characterized by: include: A processor and a memory, the memory is used to store program instructions, and the processor is used to call the stored instructions in the memory to execute the inter-reference station ambiguity resolution method for the full-constellation Beidou hybrid signal as described in any one of claims 1 to 9.

Images