BD2 and BD3 combined baseline atmospheric delay extraction method and device between reference stations

Abstract

The invention discloses a method and a device for extracting baseline atmospheric delay between base stations by combining BD2 and BD3, and the method comprises the steps: respectively determining three-frequency wide-lane ambiguity fixed solutions of BD2 and BD3, carrying out the constraint of a wide-lane ionosphere extracted based on a pseudo-range non-geometric combination, building a dual-frequency wide-lane observation equation sharing frequency points B1I and B3I, determining a BDS dual-frequency wide-lane ambiguity fixed solution, and carrying out the calculation of the BDS dual-frequency wide-lane ambiguity fixed solution. And unifying the three-frequency wide-lane ambiguity fixed solutions of the BD2 and the BD3 to a reference star of the BDS combined system to obtain a BDS wide-lane ambiguity final solution, establishing a double-frequency ionosphere-free observation equation sharing frequency points B1I and B3I, determining original ambiguity fixed solutions respectively corresponding to the frequency points B1I and B3I, and determining the original ambiguity fixed solutions of the frequency points B1I and B3I. According to the method, the double-difference troposphere wet delay and the double-difference ionosphere delay of the base line AB between the base stations are extracted in combination with the virtual frequency point technology, the respective three-frequency signals and advantages of the BD2 and the BD3 are fully used, the integrity of the correction number generated by the network RTK based on the base line atmospheric delay is ensured, the service range and the service capability of the network RTK are improved, and the overall service quality of the network RTK is improved.

Description

Technical Field

[0001] This article relates to the field of Beidou satellite navigation and positioning, and in particular to a method and device for extracting baseline atmospheric delay between reference stations combined with BD2 and BD3. Background Art

[0002] At present, the most common network RTK (Real-Time Kinematic) service mode is VRS (Virtual Reference Station). The basic equation for VRS to generate correction numbers is formula (1):

[0003]

[0004] In formula (1), the meanings of the variables are as follows: △ is the single difference operator between stations; is the station-satellite double difference operator; i represents the satellite with the Beidou system satellite number i; REF represents the reference satellite number of the system when making double differences; V represents the grid center; M represents the main reference station selected to generate VRS; f represents the fth frequency point; P is the pseudorange observation value, unit: m; λ is the carrier wavelength, unit: m; is the phase observation value, unit: week; ρ is the spatial geometric distance from the base station or grid center to the satellite; T d is the tropospheric interference delay on the propagation path; T w is the tropospheric wet delay on the propagation path; I is the ionospheric delay on the propagation path.

[0005] In formula (1) and Generally, the tropospheric wet delay and ionospheric delay of the baseline connected to the main reference station are obtained through atmospheric modeling. and It is an unknown item and requires the user terminal to perform double difference elimination within one system when performing RTK positioning. This requires that satellite i and the reference star REF belong to the same system. The RTK algorithms currently used in user terminals often treat BeiDou-2 (BD2) and BeiDou-3 (BD3) as the same system and only select one reference star for processing. However, on the server side of network RTK, in order to make full use of the multiple frequency combinations of the BeiDou system to improve the effect of fixing the baseline ambiguity, the current common method is to divide BeiDou into two systems, BeiDou-2 and BeiDou-3, and then perform three-frequency or even multi-frequency ambiguity resolution. The atmospheric correction number generated in this way will exist in the reference stars of the BeiDou-2 and BeiDou-3 systems. When the user terminal (i.e., the mobile station) receives the correction number and performs double difference, if BeiDou-2 and BeiDou-3 are treated as one system, there will always be and It is difficult to eliminate; therefore, the current network RTK server generates atmospheric correction numbers for the BeiDou-2 and BeiDou-3 systems when processing BeiDou data, and treats BeiDou-2 and BeiDou-3 as one system for RTK when processing BeiDou data on the user terminal. For satellites in BD2 and BD3, there is a problem that the single-difference ionospheric and tropospheric delays of the reference satellites cannot be eliminated, and the quality of network RTK service is low. Summary of the invention

[0006] The embodiments of the present application provide a method and device for extracting baseline atmospheric delay between reference stations combining BD2 and BD3, which fully utilizes the three-frequency signals of BD2 and BD3, ensures the integrity of the correction numbers generated by network RTK based on baseline atmospheric delay, improves the service scope and service capabilities of network RTK, and improves the overall service quality of network RTK.

[0007] On the one hand, an embodiment of the present application provides a method for extracting baseline atmospheric delay between reference stations in combination with BD2 and BD3. The method is applied to a network RTK server, and the following steps are performed between every two reference stations A and B, including:

[0008] Based on the three frequency signals B1I, B3I and B2I of BD2, double difference operation and ambiguity resolution are performed to determine the fixed solution of BD2 three-band wide lane ambiguity. Based on the three frequency signals B1I, B3I and B2a of BD3, double difference operation and ambiguity resolution are performed to determine the fixed solution of BD3 three-band wide lane ambiguity. Among them, the reference star of BD2 is j BD2 BD3's reference star is j BD3 ;

[0009] J BD2 and j BD3 The satellite with a higher medium altitude angle is set as the reference satellite j of the BDS joint system, and the satellite with a lower altitude angle is set as the conversion satellite i c , constraining the wide lane ionosphere extracted based on the pseudorange geometry-free combination in the BDS joint system, establishing the dual-frequency wide lane observation equations of the common frequency points B1I and B3I of BD2 and BD3, and determining the BDS dual-frequency wide lane ambiguity fixed solution of the BDS joint system based on the Kalman filtering of the dual-frequency wide lane observation equations, wherein the BDS joint system includes BD2 and BD3;

[0010] The conversion satellite wide lane ambiguity is determined in the BDS dual-frequency wide lane ambiguity fixed solution, and the BD2 three-frequency wide lane ambiguity fixed solution is converted based on the conversion satellite wide lane ambiguity. and the BD3 three-band wide lane ambiguity fixed solution Unified to the reference star j, the final solution of BDS wide lane ambiguity is obtained

[0011] Establish the dual-frequency ionosphere-free observation equation of the common frequency points B1I and B3I, and determine the ionosphere-free combined ambiguity floating-point solution based on the Kalman filter of the dual-frequency ionosphere-free observation equation, and combine the ionosphere-free combined ambiguity floating-point solution and the BDS wide lane ambiguity final solution Determine the original ambiguity fixed solution of the frequency point B1I and the original ambiguity fixed solution of the frequency point B3I

[0012] based on and Extract the double difference tropospheric wet delay of the baseline AB between the reference stations; based on and The double difference ionospheric delay of the baseline AB between the reference stations is extracted in combination with the virtual frequency point technology, wherein the atmospheric delay of the baseline AB between the reference stations includes the double difference tropospheric wet delay and the double difference ionospheric delay.

[0013] On the other hand, an embodiment of the present application further provides a baseline atmospheric delay extraction device between reference stations in conjunction with BD2 and BD3, including a memory and a processor;

[0014] The memory is used to store the baseline atmospheric delay extraction program between reference stations combined with BD2 and BD3;

[0015] The processor is used to read the baseline atmospheric delay extraction program between reference stations combined with BD2 and BD3, and perform the baseline atmospheric delay extraction method between reference stations combined with BD2 and BD3 as described in the above embodiment.

[0016] Compared with the related art, a method and device for extracting baseline atmospheric delay between reference stations combining BD2 and BD3 in an embodiment of the present application fully utilizes the advantages of the three-frequency signals and three-frequency combinations of BeiDou-2 and BeiDou-3, supports the situation when BeiDou-2 and BeiDou-3 have only two common frequency points, B1I and B3I, and realizes the fast and accurate fixation of wide-lane ambiguity. When fixing the dual-frequency wide-lane ambiguity of the BDS joint system, the wide-lane ionosphere extracted based on pseudo-range geometry-free combination is used for constraint, thereby improving the accuracy of the fixed dual-frequency wide-lane ambiguity. The wide-lane ambiguity of a conversion satellite is used as a "bridge" to unify the fixed values ​​of the wide-lane ambiguity of BeiDou-2 and BeiDou-3 satellites on the same reference star, thereby avoiding the risk of systematic errors in user terminals. The integrity of the baseline atmospheric delay data is ensured by establishing a virtual frequency point in the reference star, thereby ensuring the integrity of the correction number generated by the network RTK based on the baseline atmospheric delay, thereby improving the service scope and service capabilities of the network RTK, and improving the overall service quality of the network RTK.

[0017] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0019] Figure 1 This is a flow chart of a method for extracting baseline atmospheric delay between reference stations in combination with BD2 and BD3 according to an embodiment of the present application;

[0020] Figure 2 This is a schematic diagram of an inter-reference station baseline atmospheric delay extraction device combining BD2 and BD3 according to an embodiment of the present application. DETAILED DESCRIPTION

[0021] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0022] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0023] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0024] RTK has become the mainstream method of high-precision positioning due to its fast convergence speed and high positioning accuracy. However, it requires that the distance between the base station and the mobile station should not be too far (generally considered to be within 15 kilometers), otherwise the convergence time will be prolonged and the positioning accuracy will be greatly reduced. To solve this problem, domestic and foreign scholars have proposed the network RTK (full name Net-RTK, referred to as NRTK) technology, which is divided into two parts: the server and the user terminal, and mainly includes three steps: 1. The server performs ambiguity resolution of the baseline between the base stations and baseline atmospheric delay extraction; 2. The server generates virtual correction numbers through atmospheric modeling and plays them to the user; 3. The user terminal receives the virtual correction number for RTK positioning with extremely short baseline or zero baseline; Among them, the ambiguity resolution of the baseline between the base stations by the server is the key to network RTK. How to quickly converge and correctly fix the ambiguity of the baseline between the base stations determines the service quality of network RTK; for the three-frequency ambiguity fixation of the baseline between the base stations, Ronald proposed a method based on GPS (full name Global Positioning The method of resolving integer ambiguity by combining three frequencies of GPS system can speed up the ambiguity fixation of GPS; Tang Weiming, Pan Shuguo and others proposed a method based on step-by-step constraint to first fix the ultra-wide lane, then fix the wide lane, and finally fix the original ambiguity; Shen Mingxing and others proposed a method of three-frequency ambiguity fixation based on ionosphere-free, which can obtain better ambiguity resolution results when the ionosphere is active; Miao Ying and others proposed a method of first fixing two ultra-wide lanes, and then combining narrow lanes with geometry-free and ionosphere-free combination to achieve rapid fixation of three-frequency ambiguity.

[0025] Up to now, the Beidou Navigation and Positioning System (BDS) includes Beidou-2 (BD2) and Beidou-3 (BD3) satellites, which can broadcast observation data of six different frequencies, namely B1I, B2I / B2b, B3I, B1C, B2a, and B2a+b, to users. Beidou-2 satellites can broadcast three signals, namely B1I, B2I, and B3I, and Beidou-3 can broadcast six signals, namely B1I, B3I, B1C, B2a, B2b, and B2a+b. However, due to the fact that the versions of GNSS (Global Navigation Satellite System) receivers or boards are too old or not upgraded, many domestic CORS (Continuous Operational Reference The base stations of the BeiDou System often do not support all six frequencies of the BeiDou-3. Currently, many base stations only support the B1I, B2I, and B3I signals of the BeiDou-2 and the B1I, B3I, B1C, and B2a signals of the BeiDou-3. For the observation data of such base stations, the only signals that can be used between the BeiDou-2 and BeiDou-3 are B1I and B3I. In this case, the three-frequency ambiguity fixing strategy proposed by the above scholars cannot be used directly. The current common solution is for the server to treat BeiDou-2 and BeiDou-3 as two systems. The three-frequency differential positioning method of BeiDou-2 and BeiDou-3 has been studied by scholars such as Shao Huichao, but this method is based on the B2I and B2b signals with common frequencies of BeiDou-2 and BeiDou-3, and does not solve the problem when there are only two identical frequency data of B1I and B3I between BeiDou-2 and BeiDou-3 at the CORS station.

[0026] The embodiment of the present application provides a method for extracting baseline atmospheric delay between reference stations in combination with BD2 and BD3. The method is applied to the server of network RTK, and steps S100-S500 are performed between every two reference stations A and B, such as Figure 1 As shown:

[0027] S100: Perform double difference calculation and ambiguity resolution based on the three frequency signals B1I, B3I and B2I of BD2 to determine the fixed ambiguity solution of the three-bandwidth lane of BD2. Based on the three frequency signals B1I, B3I and B2a of BD3, double difference operation and ambiguity resolution are performed to determine the fixed solution of BD3 three-band wide lane ambiguity. Among them, the reference star of BD2 is j BD2 BD3's reference star is jBD3 ;

[0028] S200: j BD2 and j BD3 The satellite with a higher medium altitude angle is set as the reference satellite j of the BDS joint system, and the satellite with a lower altitude angle is set as the conversion satellite i c , constraining the wide lane ionosphere extracted based on the pseudorange geometry-free combination in the BDS joint system, establishing the dual-frequency wide lane observation equations of the common frequency points B1I and B3I of BD2 and BD3, and determining the BDS dual-frequency wide lane ambiguity fixed solution of the BDS joint system based on the Kalman filtering of the dual-frequency wide lane observation equations, wherein the BDS joint system includes BD2 and BD3;

[0029] S300: Determine the conversion satellite wide lane ambiguity in the BDS dual-frequency wide lane ambiguity fixed solution, and convert the BD2 triple-frequency wide lane ambiguity fixed solution based on the conversion satellite wide lane ambiguity and the BD3 three-band wide lane ambiguity fixed solution Unified to the reference star j, the final solution of BDS wide lane ambiguity is obtained

[0030] S400: Establish the dual-frequency ionosphere-free observation equations of the common frequency points B1I and B3I, and determine the ionosphere-free combined ambiguity floating-point solution based on the Kalman filter of the dual-frequency ionosphere-free observation equation, and combine the ionosphere-free combined ambiguity floating-point solution and the BDS wide lane ambiguity final solution Determine the original ambiguity fixed solution of the frequency point B1I and the original ambiguity fixed solution of the frequency point B3I

[0031] S500: Based on and Extract the double difference tropospheric wet delay of the baseline AB between the reference stations; based on and The double difference ionospheric delay of the baseline AB between the reference stations is extracted in combination with the virtual frequency point technology, wherein the atmospheric delay of the baseline AB between the reference stations includes the double difference tropospheric wet delay and the double difference ionospheric delay.

[0032] In this embodiment, the number of satellites in the BD3 system is a, and a satellite with the best observation data quality is selected from the a satellites as the reference satellite. BD3 , when the BD3 system is regarded as an independent system, there are a-1 non-reference stars i.

[0033] In this embodiment, the number of satellites in the BD2 system is b, and a satellite with the best observation data quality is selected from the b satellites as the reference satellite j. BD2, then when the BD2 system is regarded as an independent system, there are b-1 non-reference stars i;

[0034] In this embodiment, BD2 and BD3 form a BDS joint system. There are a+b satellites in the BDS joint system. BD2 and j BD3 The satellite with a medium and high altitude angle is set as the reference star j of the BDS joint system. Then, there are a total of n=a+b-1 non-reference stars i in the BDS joint system.

[0035] In this embodiment, when executing step S100, BD2 and BD3 are respectively regarded as independent systems. In the BD2 system, the three-frequency combination B1I, B3I and B2I of BD2 is used to obtain the three-frequency wide lane ambiguity fixed solution. In the BD3 system, the three-frequency combination B1I, B3I and B2a of BD3 is used to obtain the three-frequency wide lane ambiguity fixed solution. That is, step S100 is to fix the double difference wide lane ambiguity of BD2 and BD3 respectively; when executing step S200, the reference star j of the BDS joint system is first determined, BD2+BD3 is used as the BDS joint system, and the double difference wide lane ambiguity of the BDS joint system is fixed based on the common frequencies B1I and B3I of BD2 and BD3 in the BDS joint system; when executing step S300, the double difference wide lane ambiguity obtained in step S100 is fixed. Unified to the reference star j of the BDS joint system, the final solution of the BDS wide lane ambiguity is obtained By executing step S400, the double-difference original ambiguity of the common frequencies B1I and B3I of the BDS joint system is fixed; by executing step S500, the ionosphere-free and geometry-free combination extraction of the baseline AB atmospheric delay between reference stations under known ambiguity is realized, wherein the double-difference tropospheric wet delay is independent of the frequency point, the double-difference ionospheric delay is related to the frequency point, and the baseline AB between reference stations refers to the line between reference station A and reference station B.

[0036] In this embodiment, after executing steps S100-S500, the obtained double-difference tropospheric wet delay and double-difference ionospheric delay can be used to perform atmospheric modeling and generate VRS correction numbers. The obtained VRS correction numbers are virtual correction numbers, and some satellites also have virtual frequency points. When the user terminal performs station-satellite double difference calculations, the data of the virtual frequency points will not be used or will be eliminated, which will not affect the final service effect. At the same time, the obtained VRS correction numbers are obtained in the BDS joint system and are based on the results of the same reference satellite, so no systematic deviation will occur in the user terminal.

[0037] In this embodiment, BeiDou is divided into BeiDou-2 system and BeiDou-3 system at the server end of network RTK, and reference satellites are selected in the two systems to determine the three-frequency wide-lane ambiguity fixed solution. Then, the BDS joint system is used as a system to select a reference star to solve the wide-lane ambiguity, and a satellite is selected as a "bridge" to convert the three-frequency wide-lane ambiguity fixed solution to the same reference star. Finally, the original ambiguity is fixed and the baseline atmospheric delay between reference stations is extracted, thereby effectively supporting the RTK positioning of user terminals.

[0038] The baseline atmospheric delay extraction method for the combined BD2 and BD3 reference stations of this embodiment makes full use of the advantages of the three-frequency signals and three-frequency combinations of BeiDou-2 and BeiDou-3, supports the situation when BeiDou-2 and BeiDou-3 have only two common frequency points, B1I and B3I, and realizes the fast and accurate fixation of wide-lane ambiguity. When fixing the dual-frequency wide-lane ambiguity of the BDS joint system, the wide-lane ionosphere extracted based on pseudo-range geometry-free combination is used for constraint, which improves the accuracy of the fixed dual-frequency wide-lane ambiguity. The wide-lane ambiguity of a conversion satellite is used as a "bridge" to unify the fixed values ​​of the wide-lane ambiguity of BeiDou-2 and BeiDou-3 satellites on the same reference star, avoiding the risk of systematic errors in user terminals. The integrity of the baseline atmospheric delay data is ensured by establishing virtual frequency points in the reference star, thereby ensuring the integrity of the correction numbers generated by network RTK based on the baseline atmospheric delay, improving the service scope and service capabilities of network RTK, and improving the overall service quality of network RTK.

[0039] In an exemplary embodiment, the step S100 of "performing double difference calculation and ambiguity resolution based on the three frequency point signals B1I, B3I and B2I of BD2 to determine the fixed ambiguity resolution of the three-bandwidth lanes of BD2" is performed. ", BD2 is used as an independent system, and steps S110-S140 may be included:

[0040] S110: Using the reference star BD2 Calculate the first double-difference pseudorange observation value corresponding to each non-reference star i in BD2 and the first double-difference phase observation Wherein, k=1, 2, 3, when k=1 it represents B1I, when k=2 it represents B3I, when k=3 it represents B2I;

[0041] S120: According to the frequency point signals B3I and B2I and Constructing the first MW formula to calculate the single epoch solution of the first ultra-wide lane ambiguity And Round off to get the first ultra-wide lane ambiguity fixed solution Wherein, the subscript (0, 1, -1) represents the first ultra-wide lane combination coefficient of BD2;

[0042] S130: Calculate the first double-difference satellite-to-ground distance using the precise coordinates of the reference stations A and B Calculate the first double-difference tropospheric delay using the NMF model proposed by Neill Using the frequency signals B1I, B3I and B2I Establishing the second ultra-wide lane observation value based on and Obtain the single epoch solution for the second ultra-wide lane ambiguity right Perform Hatch filtering on multiple epochs to obtain the average solution right Rounding off to get the second ultra-wide lane ambiguity fixed solution Among them, the subscripts (1, -5, 4) represent the second ultra-wide lane combination coefficient of BD2;

[0043] S140: According to the first linear relationship The BD2 three-bandwidth lane ambiguity fixed solution is obtained The subscripts (1, -1, 0) represent the three-bandwidth lane ambiguity coefficients of BD2.

[0044] In this embodiment, steps S110-S140 are performed with BD2 as an independent system. In the BD2 system, BD2 is a reference star, and the other b-1 satellites are non-reference stars.

[0045] In this embodiment, when executing step S110, station-satellite double difference calculation is performed for each non-reference satellite i at frequency points B1I, B3I and B2I to obtain the first double difference pseudorange observation value and the first double-difference phase observation The calculation formula is formula (2) and (3):

[0046]

[0047] In formulas (2) and (3), and are the pseudo-range observation value and phase observation value of the reference station A to the non-reference satellite i at the frequency point k, and is the pseudo-range observation value and phase observation value of the reference station B to the non-reference satellite i at the frequency point k, and The reference station A is the reference star j BD2 The pseudorange observation value and phase observation value at frequency point k, and The reference station B is the reference star j BD2 Pseudorange observation value and phase observation value at frequency point k, k=1, 2, 3, when k=1 it represents B1I, when k=2 it represents B3I, when k=3 it represents B2I, i=1, 2,...b-1.

[0048] In this embodiment, when executing step S120, the frequency point signals B3I and B2I obtained in step S110 are and The first MW formula is constructed to calculate the single epoch solution of the first ultra-wide lane ambiguity of BD2 The first MW formula is formula (4):

[0049]

[0050] In formula (4), subscript 2 represents frequency point B3I, subscript 3 represents frequency point B2I, and f 2 is the frequency of frequency point B3I, f 3 is the frequency of frequency point B2I, λ 2 is the wavelength of frequency point B3I, λ 3 is the wavelength of frequency point B2I; due to the frequency difference f between frequency points B3I and B2I 2 -f 3 The combined wavelength of the B3I and B2I signals is very long, which can be corrected by rounding off. The first ultra-wide lane ambiguity fixed solution of BD2 is obtained by rounding

[0051] In this embodiment, when executing step S130, the frequency signals B1I, B3I and B2I are used. The second ultra-wide lane observation value of BD2 The composition formula is formula (5):

[0052]

[0053] based on and Obtain the single epoch solution for the second ultra-wide lane ambiguity Formula (6) can be used:

[0054]

[0055] In formula (6), represents the combined wavelength, λ 1 is the wavelength of frequency point B1I, λ 2 is the wavelength of frequency point B3I, λ 3is the wavelength of the frequency point B2I. Since the second ultra-wide lane combination of BD2 is an ionosphere weakening combination, the influence of the ionosphere can be ignored when the ionosphere is not super active or scintillation. Since the combined ambiguity will be affected by the combined noise, the average solution can be calculated by Hatch filtering. The calculation formula is formula (7):

[0056]

[0057] In formula (7), n represents the number of epochs from the start time of Hatch filtering to time t. Since the combined wavelength λ of the second ultra-wide lane combination (1,-5,4) is longer, and the noise is weakened after Hatch filtering, which can be corrected by rounding The second ultra-wide lane ambiguity fixed solution of BD2 is obtained by rounding

[0058] In this embodiment, when executing step S140, the BD2 three-bandwidth lane ambiguity fixed solution is obtained according to the first linear relationship: The first linear relationship is formula (8):

[0059]

[0060] In formula (8), That is, the second ultra-wide lane ambiguity fixed solution of BD2 obtained in step S130, That is, the first ultra-wide lane ambiguity fixed solution of BD2 obtained in step S120.

[0061] In an exemplary embodiment, the step S100 of "performing double difference operation and ambiguity resolution based on the three frequency point signals B1I, B3I and B2a of BD3 to determine the fixed ambiguity resolution of the three-bandwidth lanes of BD3" is performed. ", BD3 is used as an independent system, and steps S150-S180 may be included:

[0062] S150: With the reference star j BD3 Calculate the second double-difference pseudorange observation value corresponding to each non-reference star i in BD3 and the second double-difference phase observation Wherein, k = 1, 2, 3, when k = 1, it represents B1I, when k = 2, it represents B3I, when k = 3, it represents B2a;

[0063] S160: According to the frequency point signals B3I and B2a and The second MW formula is constructed to calculate the single epoch solution of the first ultra-wide lane ambiguity And Round off to get the first ultra-wide lane ambiguity fixed solution And record The parity of , where the subscript (0, 1, -1) represents the first ultra-wide lane combination coefficient of BD3;

[0064] S170: Calculate the second double-difference satellite-to-ground distance using the precise coordinates of the reference stations A and B Calculation of the second double-difference tropospheric delay using the NMF model proposed by Neill Using the frequency signals B1I, B3I and B2a Establishing the second ultra-wide lane observation value based on and Obtain the single epoch solution for the second ultra-wide lane ambiguity right Perform Hatch filtering on multiple epochs to obtain the average solution right The second ultra-wide lane ambiguity fixed solution is obtained by rounding up and rounding down respectively. Alternative solution and exist and Select and Parity is the same as the second ultra-wide lane ambiguity fixed solution Among them, the subscript (2, -7, 5) represents the second ultra-wide lane combination coefficient of BD3;

[0065] S180: According to the second linear relationship The BD3 three-bandwidth lane ambiguity fixed solution is obtained The subscripts (1, -1, 0) represent the three-bandwidth lane ambiguity coefficients of BD3.

[0066] In this embodiment, the execution of steps S150-S180 is based on BD3 as an independent system. In the BD3 system, BD3 is a reference star, and the other a-1 satellites are non-reference stars.

[0067] In this embodiment, when executing step S150, the station-satellite double difference calculation is performed for each non-reference satellite i at the frequency points B1I, B3I and B2a to obtain the second double difference pseudorange observation value and the second double-difference phase observation The calculation formula is formula (9) and (10):

[0068]

[0069] In formulas (9) and (10), and are the pseudo-range observation value and phase observation value of the reference station A to the non-reference satellite i at the frequency point k, and is the pseudo-range observation value and phase observation value of the reference station B to the non-reference satellite i at the frequency point k, and The reference station A is the reference star j BD3 The pseudorange observation value and phase observation value at frequency point k, and The reference station B is the reference star j BD3 The pseudorange observation value and phase observation value at frequency point k, k = 1, 2, 3, when k = 1, it represents B1I, when k = 2, it represents B3I, when k = 3, it represents B2a, i = 1, 2, ... a-1.

[0070] In this embodiment, when executing step S160, the frequency signals B3I and B2a obtained in step S150 are and The second MW formula is constructed to calculate the single epoch solution of the first ultra-wide lane ambiguity of BD3 The second MW formula is formula (11):

[0071]

[0072] In formula (11), subscript 2 represents frequency point B3I, subscript 3 represents frequency point B2a, f 2 is the frequency of frequency point B3I, f 3 is the frequency of frequency point B2a, λ 2 is the wavelength of frequency point B3I, λ 3 is the wavelength of frequency point B2a; due to the frequency difference f between frequency points B3I and B2a 2 -f 3 The combined wavelength of the B3I and B2a signals is very long, which can be corrected by rounding off. Rounding to get the first ultra-wide lane ambiguity fixed solution of BD3

[0073] In this embodiment, when executing step S170, the frequency signals B1I, B3I and B2a are used. The second ultra-wide lane observation value of BD3 The composition formula is formula (12):

[0074]

[0075] based on and Obtain the single epoch solution for the second ultra-wide lane ambiguity Formula (13) can be used:

[0076]

[0077] In formula (13), represents the combined wavelength, λ 1 is the wavelength of frequency point B1I, λ 2 is the wavelength of frequency point B3I, λ 3 is the wavelength of the frequency point B2a. Since the combined ambiguity will be affected by the combined noise, the average solution can be calculated by Hatch filtering. The calculation formula is formula (14):

[0078]

[0079] In formula (14), n represents the epoch number from the start time of Hatch filtering to time t. Since the noise of the second ultra-wide lane combination of BD3 is relatively large, even after Hatch filtering, the residual may still be relatively large. Rounding may lead to fixed ambiguity errors, but according to formula (15), (2,-2,0) = 2(1,-1,0) must be an even number.

[0080] (2,-2,0)=(2,-7,5)+5·(0,1,-1) (15) Therefore, the ambiguity fixed solutions of the first ultra-wide lane (0, 1, -1) and the second ultra-wide lane (2, -7, 5) of BD3 must be the same odd or the same even (i.e., the parity is the same), so for You can use the "rounding method" to get an alternative solution Use the "truncation method" to get an alternative solution exist and The first ultra-wide lane ambiguity fixed solution of BD3 is selected in the parity Same as the second ultra-wide lane ambiguity fixed solution of BD3

[0081] In this embodiment, when executing step S180, the BD3 three-bandwidth lane ambiguity fixed solution is obtained according to the second linear relationship: The second linear relationship is formula (16):

[0082]

[0083] In formula (16), That is, the second ultra-wide lane ambiguity fixed solution of BD3 obtained in step S170, That is, the first ultra-wide lane ambiguity fixed solution of BD3 obtained in step S160.

[0084] In an exemplary embodiment, step S200 may include steps S210-S230:

[0085] S210: j BD2 and j BD3 The satellite with a higher elevation angle is set as the reference satellite j of the BDS joint system, and the satellite with a lower elevation angle is set as the conversion satellite i c , taking the reference star j as the reference, calculate the third double-difference pseudo-range observation value corresponding to each non-reference star i in the BDS joint system and the third double-difference phase observation Wherein, k=1, 2, when k=1, it represents B1I, when k=2, it represents B3I, the conversion satellite i c is one of the non-reference satellites i in the BDS joint system;

[0086] S220: According to the frequency point signals B1I and B3I Constructing double-difference pseudo-range narrow lane observations According to the frequency point signals B1I and B3I Constructing double-difference phase wide-lane observations The third double difference satellite-to-ground distance is calculated by the precise coordinates of the reference stations A and B. Calculation of double-difference tropospheric dry delay using the NMF model proposed by Neill and double difference tropospheric wet delay relative mapping function mf ij ,based on and mf ij Through the indirect adjustment principle, based on the wide lane ionosphere extracted by pseudorange without geometry combination, the dual-frequency wide lane observation equations of the common frequency points B1I and B3I of BD2 and BD3 are established, wherein the subscript (1, 1, 0) represents the narrow lane combination coefficient of the BDS joint system, and the subscript (1, -1, 0) represents the wide lane combination coefficient of the BDS joint system;

[0087] S230: Obtain the current epoch dual-bandwidth lane ambiguity floating-point solution of the BDS joint system based on the Kalman filter of the dual-bandwidth lane observation equation Through the LAMBDA method Search and take the optimal solution as the BDS dual-band wide lane ambiguity fixed solution of the BDS joint system, wherein the BDS dual-band wide lane ambiguity fixed solution includes n values n There is a one-to-one correspondence with the non-reference satellite i in the BDS joint system, and n is the number of non-reference satellites i in the BDS joint system.

[0088] In this embodiment, the execution of steps S210-S230 is based on the BDS joint system. In the BDS joint system, j BD2 and j BD3 The satellite with a higher medium altitude angle is set as reference star j, and the other a+b-1 satellites are non-reference stars. BD2 and j BD3 Satellites with medium and low altitude angles are conversion satellites. c ,i c It is one of the other a+b-1 non-reference stars.

[0089] In this embodiment, when executing step S210, the station-satellite double difference calculation is performed for each non-reference satellite i at the common frequency points B1I and B3I to obtain the third double difference pseudorange observation value and the third double-difference phase observation For example, when j BD2 When the reference star j is j, for the other b-1 non-reference stars in BD2, the first double-difference pseudo-range observation value obtained in step S110 can be As The first double-difference phase observation value obtained in step S110 is As For a non-reference star in BD3, the third double-difference pseudorange observation value can be calculated using formulas (2) and (3): and the third double-difference phase observation However, at this time, i in formula (2) and (3) represents each satellite in BD3; after executing step S210, the third double-difference pseudo-range observation values ​​corresponding to the frequency points B1I and B3I of a+b-1 non-reference satellites are obtained. and the third double-difference phase observation Wherein, k = 1, 2, when k = 1, it represents B1I, when k = 2, it represents B3I, i = 1, 2, ... a + b - 1; when j BD3 When the reference star j is j, for the other a-1 non-reference stars in BD3, the second double-difference pseudo-range observation value obtained in step S150 can be As The second double-difference phase observation value obtained in step S150 As For the b non-reference stars in BD2, the third double-difference pseudorange observation value can be calculated using formulas (9) and (10): and the third double-difference phase observation However, at this time, i in formulas (9) and (10) represents each satellite in BD2; after executing step S210, the third double-difference pseudo-range observation values ​​corresponding to the frequency points B1I and B3I of a+b-1 non-reference satellites are obtained. and the third double-difference phase observation Among them, k=1, 2, when k=1 it represents B1I, when k=2 it represents B3I, i=1, 2, ...a+b-1.

[0090] In this embodiment, when executing step S220, the dual-bandwidth lane observation equation of the common frequency points B1I and B3I of BD2 and BD3, that is, the dual-bandwidth lane observation equation of the BDS joint system is established as formula (17):

[0091]

[0092] In formula (17), Represents the double-difference pseudo-range narrow lane observation values ​​of all non-reference satellites in the BDS joint system and The difference is shown in formula (18); Represents the double-difference phase wide-lane observations of all non-reference stars in the BDS joint system and The difference is shown in formula (19); represents the double-difference wide-lane ionospheric delay extracted by the geometry-free combination of B1I and B3I double-difference pseudoranges for all non-reference satellites in the BDS joint system, that is, the wide-lane ionosphere extracted based on the pseudorange geometry-free combination constrains the dual-frequency wide-lane observation equation, as shown in formula (20); In formulas (17)-(20), n = a + b-1, represents the total number of non-reference satellites in the BDS joint system, and λ in formulas (17) and (19) is (1,-1,0) represents the combined wavelength of the wide lane (1, -1, 0) of the BDS joint system; in formula (20), λ 1 is the wavelength of frequency point B1I, λ 2 is the wavelength of frequency B3I, f 1 is the frequency of frequency point B1I, f 2 is the frequency of frequency point B3I, subscript 1 represents frequency point B1I, subscript 2 represents frequency point B3I; in formula (17), I represents the unit matrix, MF = [mf 1j ,mf 2f ,…,mf nf ] T ; τ = [RZTD], which represents the relative zenith tropospheric wet delay parameter; It represents the wide-lane combined double-difference ionospheric delay parameters of each reference satellite in the BDS joint system; It represents the wide lane combined double difference ambiguity parameters of each reference satellite in the BDS joint system; and They represent the narrow-lane combined observation value, wide-lane combined observation value and wide-lane combined ionospheric correction number of the common frequency points B1I and B3I respectively;

[0093]

[0094] In this embodiment, when executing step S230, first, the parameters of the Kalman filter can be initialized, using RZTD 0 =0.15,δ RZTD =0.3 as the initial value and initial standard deviation of the relative zenith tropospheric wet delay parameter; through the third MW formula The initial value of the wide-lane combined double-difference ambiguity parameter of each non-reference star in the BDS joint system can be obtained. In the third MW formula, subscript 1 represents the frequency point B1I, subscript 2 represents the frequency point B3I, and the initial standard deviation of the wide-lane combined double-difference ambiguity parameter is δ N =30; the initial value of the wide-lane combined double-difference ionospheric delay parameter is 0, and the initial standard deviation of the wide-lane combined double-difference ionospheric delay parameter is δ ion =0.03·bl / 10 4 , where bl represents the length of the baseline AB between the reference stations; then Kalman filtering is performed, and in two adjacent epochs, the filtering parameters, variance, and covariance output by the first epoch are used as the initial values ​​of the second epoch, and the filtering solution of each epoch is obtained in turn.

[0095] In an exemplary embodiment, when j BD2 When j is the reference star j, BD3 is the conversion satellite i c , step S300 may include steps S310-S320:

[0096] S310: Obtain the j in the BDS dual-band wide lane ambiguity fixed solution BD3 Corresponding As the converted satellite wide lane ambiguity

[0097] S320: Based on the A formula, the reference star j is obtained. In BD3, j is removed. BD3 The BDS wide lane ambiguity corresponding to each satellite other than Among them, the A formula is In the formula A, i=1, 2, ... a-1, where a is the number of satellites of BD3; As j BD3 The corresponding BDS wide lane ambiguity final solution is Based on B formula Get BD2 except j BD2The BDS wide lane ambiguity corresponding to each satellite other than In the formula B, i=1, 2, ... b-1, and b is the number of satellites of BD2.

[0098] In this embodiment, j BD2 is the reference star j, j BD3 To switch satellite i c The BDS dual-bandwidth lane ambiguity fixed solution obtained in step S230 includes n values n=a+b-1, n corresponds to a+b-1 non-reference satellites i in the BDS joint system. When executing step S310, j BD3 is one of the a+b-1 non-reference satellites, and n Get the same as j BD3 The corresponding value is used as the conversion satellite i c Wide Lane Ambiguity

[0099]

[0100] In this embodiment, when executing step S320, due to j BD2 As reference star j, the BD3 system obtained in step S180 is converted into Unified to the reference star j (i.e. j BD2 ),and and It is based on the reference star j (i.e. j BD2 ), which can be directly used as the final solution of the BDS wide lane ambiguity. So far, the final solution of the BDS wide lane ambiguity corresponding to each non-reference star in the BDS joint system is obtained.

[0101] In an exemplary embodiment, when j BD3 When j is the reference star j, BD2 is the conversion satellite i c , step S300 may include steps S330-S340:

[0102] S330: Obtain the j in the BDS dual-band wide lane ambiguity fixed solution BD2 Corresponding As the converted satellite wide lane ambiguity

[0103] S340: Based on the C formula, the reference star j is obtained, and the value of j in BD2 is obtained. BD2 The BDS wide lane ambiguity corresponding to each satellite other than Wherein, the C formula is In the formula C, i=1, 2, ... b-1, where b is the number of satellites of BD2; As j BD2 The corresponding BDS wide lane ambiguity final solution is Based on D formula Get BD3 except j BD3 The BDS wide lane ambiguity corresponding to each satellite other than In the D formula, i=1, 2, ..., a-1, where a is the number of satellites of BD3.

[0104] In this embodiment, j BD3 is the reference star j, j BD2 To switch satellite i c The BDS dual-bandwidth lane ambiguity fixed solution obtained in step S230 includes n values n=a+b-1, n There is a one-to-one correspondence with a+b-1 non-reference satellites i in the BDS joint system. When executing step S330, j BD2 is one of the a+b-1 non-reference satellites, and n Get the same as j BD2 The corresponding value is used as the conversion satellite i c Wide Lane Ambiguity

[0105]

[0106] In this embodiment, when executing step S340, due to j BD3 As the reference star j, the BD2 system obtained in step S140 is converted into Unified to the reference star j (i.e. j BD3 ),and and It is based on the reference star j (i.e. j BD3 ), which can be directly used as the final solution of the BDS wide lane ambiguity. So far, the final solution of the BDS wide lane ambiguity corresponding to each non-reference star in the BDS joint system is obtained.

[0107] In an exemplary embodiment, step S400 may include steps S410-S430:

[0108] S410: Based on Constructing ionosphere-free combined double-difference pseudorange observations based on Constructing ionospheric-free combined double-difference phase observations based on and mf ijThe dual-frequency ionosphere-free observation equations of the common frequency points B1I and B3I are established by the indirect adjustment principle;

[0109] S420: Obtain the current epoch dual-frequency ionosphere-free combined ambiguity floating-point solution of the BDS joint system based on the Kalman filter of the dual-frequency ionosphere-free observation equation

[0110] S430: Final solution based on the BDS wide lane ambiguity and Through the third linear relationship Get the floating point solution of the frequency point B1I Through the LAMBDA method Search and take the optimal solution as the original ambiguity fixed solution of the frequency point B1I Among them, in the third linear relationship, f 1 is the frequency of frequency point B1I, f 2 is the frequency of frequency point B3I, λ 1 is the wavelength of frequency point B1I, λ 2 is the wavelength of frequency B3I;

[0111] The BDS wide lane ambiguity is finally resolved according to the and Through the fourth linear relationship Obtain the original ambiguity fixed solution of the frequency point B3I

[0112] In this embodiment, when executing step S410, the That is, the third double-difference pseudo-range observation value obtained in step S210 Formation The formula is formula (21); the adopted That is, the third double-difference phase observation value obtained in step S210 Formation The formula is formula (22). In formulas (21) and (22), subscript 1 represents frequency point B1I, subscript 2 represents frequency point B3I, and f 1 is the frequency of frequency point B1I, f 2 is the frequency of frequency point B3I, λ 1 is the wavelength of frequency point B1I, λ 2 is the wavelength of frequency B3I;

[0113]

[0114] The method used in step S410 and mf ijThat is, the third double-difference satellite-to-ground distance, double-difference tropospheric dry delay and double-difference tropospheric wet delay relative mapping function obtained in step S220 are used to establish the dual-frequency ionosphere-free observation equation of the common frequency points B1I and B3I through the indirect adjustment principle as formula (23):

[0115]

[0116] In formula (23), the meanings of MF, I and τ are exactly the same as those in formula (17). is the ionospheric-free combined double-difference pseudorange observation value of all non-reference satellites in the BDS joint system and The difference is shown in formula (24); is the ionospheric-free combined double-difference phase observation value of all non-reference satellites in the BDS joint system and The difference is as shown in formula (25). In formulas (24) and (25), n = a + b - 1;

[0117]

[0118] In formula (23), η IF Each element in represents the double-difference ionospheric-free combined ambiguity parameters corresponding to each non-reference star in the BDS joint system; They respectively represent the correction numbers of the pseudorange and phase double-difference ionospheric-free combined observation values ​​of each non-reference star in the BDS joint system.

[0119] In this embodiment, when executing step S420, first, the parameters of the ionospheric-free Kalman filter need to be initialized, using RZTD 0 =0.15,δ RZTD = 0.3 as the initial value and initial standard deviation of the relative zenith tropospheric wet delay parameter; The initial value of the ionospheric-free combined double-difference ambiguity parameter of each reference star i in the BDS joint system can be obtained. The initial standard deviation of the ionospheric-free combined double-difference ambiguity parameter is δ N =30; then, Kalman filtering is performed. In two adjacent epochs, the filtering parameters, variance, and covariance outputted from the first epoch are used as the initial values ​​of the second epoch, and the filtering solution of each epoch is obtained in turn.

[0120] In this embodiment, when executing step S430, the BDS wide lane ambiguity final solution obtained in step S320 or S340 is and step S420 The floating point solution of frequency point B1I is obtained through the third linear relationship And through the LAMBDA method Search and take the optimal solution as the original ambiguity fixed solution of frequency point B1I The BDS wide lane ambiguity obtained in step S320 or S340 is finally resolved. And the original ambiguity fixed solution of frequency point B1I obtained in step S430 The original ambiguity fixed solution of frequency point B3I is obtained by the fourth linear relationship:

[0121] In an exemplary embodiment, the “based on and Extracting the double difference tropospheric wet delay of the baseline AB between the reference stations may include step S510:

[0122] S510: Using E formula Extract the double difference tropospheric wet delay of the baseline AB between the reference stations

[0123] In this embodiment, the double difference tropospheric wet delay of the baseline AB between the reference stations is extracted by the ionosphere-free combination of the known ambiguity fixed solution. In the E formula, is the ionospheric-free combined double-difference phase observation value obtained in step S410, is the third double-difference satellite-to-ground distance obtained in step S220, is the double-difference tropospheric dry delay obtained in step S220, is the original ambiguity fixed solution of the frequency point B1I obtained in step S430, is the original ambiguity fixed solution of the frequency point B3I obtained in step S430, 1 is the frequency of frequency point B1I, f 2 is the frequency of frequency point B3I, λ 1 is the wavelength of frequency point B1I, λ 2 is the wavelength of frequency B3I.

[0124] In an exemplary embodiment, the “based on and Combined with the virtual frequency point technology to extract the double difference ionospheric delay of the baseline AB between the reference stations” may include steps S520-S530-S541 or S520-S530-S542:

[0125] S520: According to the F formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B1I

[0126] In this embodiment, the double difference ionospheric delay of the inter-reference station baseline AB at the frequency point B1I is extracted by a geometry-free combination of the known ambiguity fixed solution. In the geometry-free combination F formula, The subscript 1 in represents the frequency point B1I, is the third double-difference phase observation value representing the frequency point B1I obtained in step S210, is the third double-difference phase observation value representing the frequency point B3I obtained in step S210, is the original ambiguity fixed solution of the frequency point B1I obtained in step S430, is the original ambiguity fixed solution of the frequency point B3I obtained in step S430, 1 is the frequency of frequency point B1I, f 2 is the frequency of frequency point B3I, λ 1 is the wavelength of frequency point B1I, λ 2 is the wavelength of frequency B3I;

[0127] S530: According to G formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B3I

[0128] In this embodiment, in the G formula, The subscript 2 in the above formula represents the frequency point B3I, f 1 is the frequency of frequency point B1I, f 2 is the frequency of frequency point B3I;

[0129] S541: When j BD2 When is the reference star j:

[0130] For the j in BD2 BD2 For all satellites other than Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2I in, The subscript 3 in the figure represents the frequency point B2I of BD2, f 1 is the frequency of frequency point B1I, f 3 is the frequency of frequency point B2I, i=1, 2, ... b-1, b is the number of satellites of BD2;

[0131] In the reference star BD2 The virtual frequency point B2a is constructed on the BD3, and for each satellite in BD3, according to the H formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2a in, The subscript 3 in the figure represents the frequency point B2a, f of BD3. 1 is the frequency of frequency point B1I, f 3 is the frequency of frequency point B2a, i=1, 2, ...a, a is the number of satellites of BD3;

[0132] S542: When j BD3 When is the reference star j:

[0133] In the reference star BD3 Construct a virtual frequency point B2I on the BD2, and for each satellite in BD2, according to the H formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2I in, The subscript 3 in the figure represents the frequency point B2I of BD2, f 1 is the frequency of frequency point B1I, f 3 is the frequency of frequency point B2I, i = 1, 2, ... b, b is the number of satellites of BD2;

[0134] For the removal of j in BD3 BD3 For satellites other than Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2a in, The subscript 3 in the figure represents the frequency point B2a, f of BD3. 1 is the frequency of frequency point B1I, f 3 is the frequency of frequency point B2a, i=1, 2, ... a-1, a is the number of satellites of BD3.

[0135] In this embodiment, the double difference tropospheric wet delay obtained in step S510 Regardless of the frequency point, the double difference ionospheric delay corresponding to the frequency point is obtained through steps S520-S530-S541 or S520-S530-S542. The baseline AB atmospheric delay between reference stations includes the double difference tropospheric wet delay and the double difference ionospheric delay. The double difference tropospheric wet delay and the double difference ionospheric delay can be used to model the atmosphere and generate VRS correction numbers. The obtained VRS correction numbers are virtual correction numbers. Some satellites also have virtual frequency points. When the user terminal performs station-satellite double difference calculation, the data of the virtual frequency points will not be used or will be eliminated, which will not affect the final service effect. At the same time, the obtained VRS correction numbers are obtained in the BDS joint system and are based on the results of the same reference star, so no systematic deviation will occur in the user terminal.

[0136] The embodiment of the present application also provides a device for extracting atmospheric delay between reference stations in combination with BD2 and BD3, including a memory and a processor, such as Figure 2 As shown:

[0137] The memory is used to store the baseline atmospheric delay extraction program between reference stations combined with BD2 and BD3;

[0138] The processor is used to read the baseline atmospheric delay extraction program between reference stations combined with BD2 and BD3, and perform the baseline atmospheric delay extraction method between reference stations combined with BD2 and BD3 as described in the above embodiment.

[0139] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term "computer storage medium" includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for extracting atmospheric delay between reference stations by combining BD2 and BD3, characterized in that: The method is applied to the server of the network RTK, and the following steps are performed between every two reference stations A and B, including: Based on the three frequency signals B1I, B3I and B2I of BD2, double difference operation and ambiguity resolution are performed to determine the fixed solution of BD2 three-band wide lane ambiguity. Based on the three frequency signals B1I, B3I and B2a of BD3, double difference operation and ambiguity resolution are performed to determine the fixed solution of BD3 three-band wide lane ambiguity. Among them, the reference star of BD2 is j BD2 BD3's reference star is j BD3 ; J BD2 and j BD3 The satellite with a higher medium altitude angle is set as the reference satellite j of the BDS joint system, and the satellite with a lower altitude angle is set as the conversion satellite i c , constraining the wide lane ionosphere extracted based on the pseudorange geometry-free combination in the BDS joint system, establishing the dual-frequency wide lane observation equations of the common frequency points B1I and B3I of BD2 and BD3, and determining the BDS dual-frequency wide lane ambiguity fixed solution of the BDS joint system based on the Kalman filtering of the dual-frequency wide lane observation equations, wherein the BDS joint system includes BD2 and BD3; The conversion satellite wide lane ambiguity is determined in the BDS dual-frequency wide lane ambiguity fixed solution, and the BD2 three-frequency wide lane ambiguity fixed solution is converted based on the conversion satellite wide lane ambiguity. and the BD3 three-band wide lane ambiguity fixed solution Unified to the reference star j, the final solution of BDS wide lane ambiguity is obtained Establish the dual-frequency ionosphere-free observation equation of the common frequency points B1I and B3I, and determine the ionosphere-free combined ambiguity floating-point solution based on the Kalman filter of the dual-frequency ionosphere-free observation equation, and combine the ionosphere-free combined ambiguity floating-point solution and the BDS wide lane ambiguity final solution Determine the original ambiguity fixed solution of the frequency point B1I and the original ambiguity fixed solution of the frequency point B3I based on and Extract the double difference tropospheric wet delay of the baseline AB between the reference stations; based on and The double difference ionospheric delay of the baseline AB between the reference stations is extracted in combination with the virtual frequency point technology, wherein the atmospheric delay of the baseline AB between the reference stations includes the double difference tropospheric wet delay and the double difference ionospheric delay.

2. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 1, characterized in that: The three frequency point signals B1I, B3I and B2I of BD2 are used to perform double difference operation and ambiguity resolution to determine the fixed ambiguity solution of the three-bandwidth lane of BD2. Includes: Using BD2 as a standalone system to do the following: With the reference star BD2 Calculate the first double-difference pseudorange observation value corresponding to each non-reference star i in BD2 and the first double-difference phase observation Wherein, k=1, 2, 3, when k=1 it represents B1I, when k=2 it represents B3I, when k=3 it represents B2I; According to the frequency signals B3I and B2I and Constructing the first MW formula to calculate the single epoch solution of the first ultra-wide lane ambiguity And Round off to get the first ultra-wide lane ambiguity fixed solution Wherein, the subscript (0, 1, -1) represents the first ultra-wide lane combination coefficient of BD2; The first double difference satellite-to-ground distance is calculated by the precise coordinates of the reference stations A and B. Calculate the first double-difference tropospheric delay using the NMF model proposed by Neill Using the frequency signals B1I, B3I and B2I Establishing the second ultra-wide lane observation value based on and Obtain the single epoch solution for the second ultra-wide lane ambiguity right Perform Hatch filtering on multiple epochs to obtain the average solution right Rounding off to get the second ultra-wide lane ambiguity fixed solution Among them, the subscripts (1, -5, 4) represent the second ultra-wide lane combination coefficient of BD2; According to the first linear relationship The BD2 three-bandwidth lane ambiguity fixed solution is obtained The subscripts (1, -1, 0) represent the three-bandwidth lane ambiguity coefficients of BD2.

3. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 1, characterized in that: The three frequency point signals B1I, B3I and B2a based on BD3 are double-differenced and ambiguity resolved to determine the fixed ambiguity solution of the three-bandwidth lane of BD3. Includes: Using BD3 as a standalone system to do the following: With the reference star BD3 Calculate the second double-difference pseudorange observation value corresponding to each non-reference star i in BD3 and the second double-difference phase observation Wherein, k = 1, 2, 3, when k = 1, it represents B1I, when k = 2, it represents B3I, when k = 3, it represents B2a; According to the frequency point signals B3I and B2a and The second MW formula is constructed to calculate the single epoch solution of the first ultra-wide lane ambiguity And Round off to get the first ultra-wide lane ambiguity fixed solution And record The parity of , where the subscript (0, 1, -1) represents the first ultra-wide lane combination coefficient of BD3; The second double difference satellite-to-ground distance is calculated by the precise coordinates of the reference stations A and B. Calculation of the second double-difference tropospheric delay using the NMF model proposed by Neill Using the frequency signals B1I, B3I and B2a Establishing the second ultra-wide lane observation value based on and Obtain the single epoch solution for the second ultra-wide lane ambiguity right Perform Hatch filtering on multiple epochs to obtain the average solution right The second ultra-wide lane ambiguity fixed solution is obtained by rounding up and rounding down respectively. Alternative solution and exist and Select and Parity is the same as the second ultra-wide lane ambiguity fixed solution Among them, the subscript (2, -7, 5) represents the second ultra-wide lane combination coefficient of BD3; According to the second linear relationship The BD3 three-bandwidth lane ambiguity fixed solution is obtained The subscripts (1, -1, 0) represent the three-bandwidth lane ambiguity coefficients of BD3.

4. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 1, characterized in that: The BD2 and j BD3 The satellite with a higher medium altitude angle is set as the reference satellite j of the BDS joint system, and the satellite with a lower altitude angle is set as the conversion satellite i c , constraining the wide lane ionosphere extracted based on the pseudorange geometry-free combination in the BDS joint system, establishing dual-frequency wide lane observation equations of the common frequency points B1I and B3I of BD2 and BD3, and determining the BDS dual-frequency wide lane ambiguity fixed solution of the BDS joint system based on Kalman filtering of the dual-frequency wide lane observation equations, including: performing the following operations on the BDS joint system: J BD2 and j BD3 The satellite with a higher elevation angle is set as the reference satellite j of the BDS joint system, and the satellite with a lower elevation angle is set as the conversion satellite i c , taking the reference star j as the reference, calculate the third double-difference pseudo-range observation value corresponding to each non-reference star i in the BDS joint system and the third double-difference phase observation Wherein, k=1, 2, when k=1, it represents B1I, when k=2, it represents B3I, the conversion satellite i c is one of the non-reference satellites i in the BDS joint system; According to the frequency point signals B1I and B3I Constructing double-difference pseudo-range narrow lane observations According to the frequency point signals B1I and B3I Constructing double-difference phase wide-lane observations The third double difference satellite-to-ground distance is calculated by the precise coordinates of the reference stations A and B. Calculation of double-difference tropospheric dry delay using the NMF model proposed by Neill and double difference tropospheric wet delay relative mapping function mf ij ,based on and mf ij Through the indirect adjustment principle, based on the wide lane ionosphere extracted by pseudorange without geometry combination, the dual-frequency wide lane observation equations of the common frequency points B1I and B3I of BD2 and BD3 are established, wherein the subscript (1, 1, 0) represents the narrow lane combination coefficient of the BDS joint system, and the subscript (1, -1, 0) represents the wide lane combination coefficient of the BDS joint system; The Kalman filter based on the dual-bandwidth lane observation equation obtains the current epoch dual-bandwidth lane ambiguity floating point solution of the BDS joint system Through the LAMBDA method Search and take the optimal solution as the BDS dual-band wide lane ambiguity fixed solution of the BDS joint system, wherein the BDS dual-band wide lane ambiguity fixed solution includes n values n There is a one-to-one correspondence with the non-reference satellite i in the BDS joint system, and n is the number of non-reference satellites i in the BDS joint system.

5. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 1, characterized in that: The conversion satellite wide lane ambiguity is determined in the BDS dual-frequency wide lane ambiguity fixed solution, and the BD2 three-frequency wide lane ambiguity fixed solution and the BD3 three-frequency wide lane ambiguity fixed solution are unified to the reference satellite j based on the conversion satellite wide lane ambiguity to obtain the BDS wide lane ambiguity final solution include: When BD2 When j is the reference star j, BD3 is the conversion satellite i c , do the following: Obtain the same as j in the BDS dual-band wide lane ambiguity fixed solution BD3 Corresponding As the converted satellite wide lane ambiguity Will Based on the A formula, the reference star j is obtained. In BD3, j is removed. BD3 The BDS wide lane ambiguity corresponding to each satellite other than Among them, the A formula is In the formula A, i=1, 2, ..., a-1, where a is the number of satellites of BD3; Will As j BD3 The corresponding BDS wide lane ambiguity final solution is Based on B formula Get BD2 except j BD2 The BDS wide lane ambiguity corresponding to each satellite other than In the formula B, i=1, 2, ... b-1, and b is the number of satellites of BD2.

6. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 1, characterized in that: The conversion satellite wide lane ambiguity is determined in the BDS dual-frequency wide lane ambiguity fixed solution, and the BD2 three-frequency wide lane ambiguity fixed solution and the BD3 three-frequency wide lane ambiguity fixed solution are unified to the reference satellite j based on the conversion satellite wide lane ambiguity to obtain the BDS wide lane ambiguity final solution include: When BD3 When j is the reference star j, BD2 is the conversion satellite i c , do the following: Obtain the same as j in the BDS dual-band wide lane ambiguity fixed solution BD2 Corresponding As the converted satellite wide lane ambiguity Will Based on the C formula, the reference star j is obtained, and the value of j in BD2 is obtained. BD2 The BDS wide lane ambiguity corresponding to each satellite other than Wherein, the C formula is In the formula C, i=1, 2, ..., b-1, where b is the number of satellites of BD2; Will As j BD2 The corresponding BDS wide lane ambiguity final solution is Based on D formula Get BD3 except j BD3 The BDS wide lane ambiguity corresponding to each satellite other than In the D formula, i=1, 2, ..., a-1, where a is the number of satellites of BD3.

7. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 4, characterized in that: The dual-frequency ionosphere-free observation equation of the common frequency points B1I and B3I is established, and the ionosphere-free combined ambiguity floating-point solution is determined based on the Kalman filter of the dual-frequency ionosphere-free observation equation, and the ionosphere-free combined ambiguity floating-point solution and the BDS wide lane ambiguity final solution are combined. Determine the original ambiguity fixed solution of the frequency point B1I and the original ambiguity fixed solution of the frequency point B3I include: based on Constructing ionosphere-free combined double-difference pseudorange observations based on Constructing ionospheric-free combined double-difference phase observations based on and mf ij The dual-frequency ionosphere-free observation equations of the common frequency points B1I and B3I are established by the indirect adjustment principle; The Kalman filter based on the dual-frequency ionosphere-free observation equation obtains the current epoch dual-frequency ionosphere-free combined ambiguity floating point solution of the BDS joint system The BDS wide lane ambiguity is finally resolved according to the and Through the third linear relationship Get the floating point solution of the frequency point B1I Through the LAMBDA method Search and take the optimal solution as the original ambiguity fixed solution of the frequency point B1I Wherein, in the third linear relationship, f1 is the frequency of the frequency point B1I, f2 is the frequency of the frequency point B3I, λ1 is the wavelength of frequency point B1I, λ2 is the wavelength of frequency point B3I; The BDS wide lane ambiguity is finally resolved according to the and Through the fourth linear relationship Obtain the original ambiguity fixed solution of the frequency point B3I 8. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 7, characterized in that: The basis and Extract the double difference tropospheric wet delay of the baseline AB between the reference stations, including: Using E formula Extract the double difference tropospheric wet delay of the baseline AB between the reference stations 9. The method for extracting atmospheric delay between reference stations by combining BD2 and BD3 as claimed in claim 7, characterized in that: The basis and Combined with the virtual frequency point technology, the double difference ionospheric delay of the baseline AB between the reference stations is extracted, including: According to the F formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B1I According to the G formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B3I When BD2 When is the reference star j: For the j in BD2 BD2 For all satellites other than Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2I in, The subscript 3 in represents the frequency point B2I of BD2, f1 is the frequency of the frequency point B1I, f3 is the frequency of the frequency point B2I, i=1, 2, ... b-1, b is the number of satellites of BD2; In the reference star BD2 The virtual frequency point B2a is constructed on the BD3, and for each satellite in BD3, according to the H formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2a in, The subscript 3 in represents the frequency point B2a of BD3, f1 is the frequency of the frequency point B1I, f3 is the frequency of the frequency point B2a, i=1, 2, ... a, a is the number of satellites of BD3; When BD3 When is the reference star j: In the reference star BD3 Construct a virtual frequency point B2I on the BD2, and for each satellite in BD2, according to the H formula Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2I in, The subscript 3 in represents the frequency point B2I of BD2, f1 is the frequency of the frequency point B1I, f3 is the frequency of the frequency point B2I, i=1, 2, ... b, b is the number of satellites of BD2; For the removal of j in BD3 BD3 For satellites other than Extract the double difference ionospheric delay of the baseline AB between the reference stations corresponding to the frequency point B2a in, The subscript 3 in represents the frequency point B2a of BD3, f1 is the frequency of the frequency point B1I, f3 is the frequency of the frequency point B2a, i=1, 2, ... a-1, a is the number of satellites of BD3.

10. A device for extracting atmospheric delay between reference stations in combination with BD2 and BD3, comprising a memory and a processor, characterized in that: The memory is used to store the baseline atmospheric delay extraction program between reference stations combined with BD2 and BD3; The processor is used to read the baseline atmospheric delay extraction program between reference stations combining BD2 and BD3, and perform the baseline atmospheric delay extraction method between reference stations combining BD2 and BD3 as described in any one of claims 1-9.

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