RNSS / RDSS / 5G fused satellite-ground integrated enhanced adaptive precision positioning method

Abstract

The invention discloses a satellite-ground integrated enhanced adaptive precision positioning method based on RNSS / RDSS / 5G fusion, and belongs to the technical field of satellite navigation precision positioning. According to the method, self-positioning is carried out on a user side receiver, and request information is reported to a service center through a ground 5G network or satellite RDSS communication; the service center preferably determines a positioning service mode; the service center performs satellite system and satellite optimization by adopting a PDOP method according to a selected positioning mode; the service center can support a ground 5G network or an on-satellite RDSS communication mode to return satellite correction information, atmosphere correction information and differential information; and the user side analyzes various kinds of correction information and performs model correction calculation so as to realize self-adaptive precision positioning processing. According to the invention, the situation that precise positioning cannot be realized due to the influence of a single communication means is effectively overcome, the advantages of Beidou RDSS communication are fully played, satellite-ground integrated adaptive precise positioning service in multiple modes is realized, the positioning robustness is improved, and the high-precision characteristic is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite navigation precise positioning services, and particularly relates to a space-ground integrated enhanced adaptive precise positioning method integrating RNSS / RDSS / 5G, which is applicable to space-ground integrated positioning services under various communication conditions. Background Art

[0002] With the rapid development of emerging technologies such as unmanned driving and artificial intelligence, higher requirements for positioning have been put forward in people's daily production and life. The existing space-based precise positioning services can no longer meet the needs of these industries, and the ground-based precise positioning services are restricted by communication conditions. In emergency rescue scenarios such as mountainous areas, deserts, and the sea, the precise position service requirements of users under sparse or denied network conditions cannot be met.

[0003] On July 31, 2020, the Beidou-3 global satellite navigation system was fully networked and officially provided services, providing navigation positioning and timing services for users. In addition, Beidou-3 can also provide RDSS communication services, enabling end-to-end two-way communication, which provides a new possible way for the precise positioning service mode.

[0004] Since the official operation of Beidou-3, some scholars have carried out some research work on RNSS navigation positioning and timing services and RDSS position services. However, there is no research on space-ground integrated RNSS precise positioning services specifically designed around the communication characteristics of RDSS in the existing technology. Summary of the Invention

[0005] In view of this, the present invention provides a space-ground integrated enhanced adaptive precise positioning method integrating RNSS / RDSS / 5G. The present invention can meet the interaction protocols of different user requirements, including service request protocols, service application protocols, etc., and transmits protocol information through two communication link transmission protocols, 5G or RDSS, to help users obtain precise positioning results and provide users with more reliable and robust precise position services.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A space-ground integrated enhanced adaptive precise positioning method integrating RNSS / RDSS / 5G is used to perform satellite system and satellite optimization on the positioning method requested by a user through a service center, so that the user can achieve an enhanced positioning effect with the assistance of a ground monitoring station. The communication between the user and the service center is carried out in the manner of 5G or RDSS. The service center forms various correction information required for user positioning based on all ground monitoring stations, and the satellite system used for positioning is the Beidou system or the Beidou+GPS system; the method includes the following steps:

[0008] Step 1: The user receives and parses the GNSS observation data and broadcast ephemeris information of the satellite system in real time, performs RNSS basic positioning, determines the form of the request protocol according to the user type. The request protocol is divided into two types: the approximate position transmission protocol and the position coding protocol. Among them, the approximate position transmission protocol reports the user's approximate position, positioning mode, satellite system, and service level requirements to the service center in the form of request protocol information. The position coding protocol reports the horizontal and elevation coding of the user position, positioning mode, satellite system, and service level requirements to the service center in the form of request protocol information. The service level requirements are divided into three positioning requirements: PPP-AR, PPP-RTK, and RTK.

[0009] Step 2: The service center parses the request protocol, selects the optimal positioning mode for enhanced positioning from PPP-AR, PPP-RTK, and RTK according to the distribution location information of ground monitoring stations, satellite system, and user request protocol information, and determines the correction information for enhanced positioning. The correction information is part or all of the information of satellite precise orbit correction, satellite precise clock offset correction, satellite code bias correction, satellite phase bias correction, ionospheric delay correction, tropospheric delay correction, and reference base station differential correction, reference base station coordinate information.

[0010] Step 3: The service center selects satellites preferably using the spatial position dilution of precision method according to the selected positioning mode and satellite elevation cut-off angle.

[0011] Step 4: The service center sends the positioning mode, correction information, and information of the preferably selected satellites to the user in the form of a service protocol. Among them, the positioning mode is one of PPP-AR, PPP-RTK, and RTK, and the correction information is associated with the positioning mode.

[0012] Step 5: The user receives the service protocol, parses out the relevant correction information, corrects the satellite model according to the correction information type in combination with the error model calculation method, and performs precise positioning based on the corrected satellite model.

[0013] Furthermore, 5G is preferably used for communication between the user and the service center. Only when 5G cannot be used, RDSS is used for communication.

[0014] Furthermore, the request protocol adopts an ASCII coding structure and includes two types: the approximate position transmission protocol and the position coding protocol.

[0015] The approximate position transmission protocol includes the following information:

[0016] UTC time, latitude, latitude hemisphere, longitude, longitude hemisphere, altitude, geoid height anomaly difference, positioning mode, service level requirement, satellite system requirement, check code;

[0017] The position coding protocol includes the following information:

[0018] UTC time, horizontal coding, elevation coding, positioning mode, service level requirement, satellite system requirement, check code; among them, the horizontal coding is used to represent the horizontal area, and the elevation coding is used to represent the elevation area.

[0019] Furthermore, if the user adopts the approximate position transmission protocol, the specific method of step 2 is as follows:

[0020] (211) Analyze the approximate position transmission protocol to obtain information on latitude, longitude, and altitude;

[0021] (212) Convert the user position represented by latitude, longitude, and altitude into ECEF coordinates;

[0022] (213) Calculate the distances from the user position coordinates to each ground monitoring station, find the ground monitoring station closest to the user position, and obtain the distance D1 between the user and the ground monitoring station;

[0023] (214) According to the distance D1 between the user and the ground monitoring station and the user-requested positioning mode M2, select the optimal positioning mode for enhanced positioning:

[0024] When M2 is RTK, if D1 is greater than 180 km, then the PPP-AR positioning mode is selected; if D1 is greater than 30 km and not greater than 180 km, then the PPP-RTK positioning mode is selected; if D1 is not greater than 30 km, then the RTK positioning mode is selected;

[0025] When M2 is PPP-RTK, if D1 is greater than 180 km, then the PPP-AR positioning mode is selected; otherwise, the PPP-RTK positioning mode is selected;

[0026] When M2 is PPP-AR, the PPP-AR positioning mode is selected;

[0027] (215) According to the original positioning mode M1 used by the user, the positioning system in the request protocol, and the selected optimal positioning mode, select the correction information for enhanced positioning:

[0028] If M1 is SPP and the PPP-AR mode is selected, then the correction information is satellite precise orbit, satellite precise clock offset, satellite code bias, and satellite phase bias, and the satellite system is the positioning system specified in the request protocol;

[0029] If M1 is SPP and the PPP-AR mode is selected, then the correction information is satellite phase bias;

[0030] If M1 is SPP and the PPP-RTK mode is selected, the correction information is precise satellite orbits, precise satellite clock biases, satellite code biases, satellite phase biases, ionospheric and tropospheric delay corrections;

[0031] If M1 is PPP and the PPP-RTK mode is selected, the correction information is satellite phase biases, ionospheric and tropospheric delay corrections;

[0032] If the RTK mode is selected and the positioning system is Beidou, the correction information is Beidou observation data, reference base station coordinate information;

[0033] If the RTK mode is selected and the positioning system is Beidou + GPS, the correction information is Beidou and GPS observation data and reference base station coordinate information;

[0034] If the user adopts a position coding protocol, the specific method in step 2 is as follows:

[0035] (221) The service center analyzes the position coding protocol, obtains the horizontal coding and elevation coding, and calculates the central position of the area corresponding to the horizontal coding and elevation coding, that is, the longitude, latitude, and altitude information of the coding center;

[0036] (222) Convert the longitude, latitude, and altitude information of the coding center into ECEF coordinates;

[0037] (223) Calculate the distances from the coding center to each ground monitoring station, find the ground monitoring station closest to the coding center, and obtain the distance D1 between the coding center and the ground monitoring station;

[0038] (224) According to the distance D1 between the coding center and the ground monitoring station and the user's requested positioning mode M2, select the optimal positioning mode for enhanced positioning:

[0039] When M2 is RTK, if D1 is greater than 180 km, the PPP-AR positioning mode is selected; if D1 is greater than 30 km and not greater than 180 km, the PPP-RTK positioning mode is selected; if D1 is not greater than 30 km, the RTK positioning mode is selected;

[0040] When M2 is PPP-RTK, if D1 is greater than 180 km, the PPP-AR positioning mode is selected; otherwise, the PPP-RTK positioning mode is selected;

[0041] When M2 is PPP-AR, the PPP-AR positioning mode is selected;

[0042] (225) According to the original positioning mode M1 used by the user, the positioning system in the request protocol, and the selected optimal positioning mode, select the correction information for enhanced positioning:

[0043] If M1 is SPP and the PPP-AR mode is selected, the correction information is the precise satellite orbit, precise satellite clock bias, satellite code bias, and satellite phase bias, and the satellite system is the positioning system specified in the request protocol;

[0044] If M1 is SPP and the PPP-AR mode is selected, the correction information is the satellite phase bias;

[0045] If M1 is SPP and the PPP-RTK mode is selected, the correction information is the precise satellite orbit, precise satellite clock bias, satellite code bias, satellite phase bias, ionospheric and tropospheric delay corrections;

[0046] If M1 is PPP and the PPP-RTK mode is selected, the correction information is the satellite phase bias, ionospheric and tropospheric delay corrections;

[0047] If the RTK mode is selected and the positioning system is Beidou, the correction information is Beidou observation data and reference base station coordinate information;

[0048] If the RTK mode is selected and the positioning system is Beidou+GPS, the correction information is Beidou, GPS observation data, and reference base station coordinate information.

[0049] Furthermore, the specific method of step 3 is as follows:

[0050] (301) Based on the broadcast ephemeris of each ground monitoring station, through ephemeris merging, obtain the full constellation broadcast ephemeris, and then calculate the positions of visible satellites within the next 3 minutes based on this ephemeris;

[0051] (302) Obtain the feature point position, and then calculate the elevation angle of each satellite based on the position of the feature point and each satellite;

[0052] If the request protocol transmitted back by the user adopts the approximate position transmission protocol, the feature point is the user position, that is, the user's latitude, longitude, and altitude;

[0053] If the request protocol transmitted back by the user adopts the position coding protocol, the feature point is the position of the coding center, and the user obtains this position through the decoding book;

[0054] (303) According to the preset satellite cut-off elevation angle requirement, filter out all satellites that meet the requirements;

[0055] (304) Use the spatial position dilution of precision method to filter the satellites that meet the requirements, and sequentially eliminate the satellites with the least contribution to positioning until the satellite number requirement is met;

[0056] Among them, if the satellite system used for positioning is the Beidou system, the satellite number requirement is 12, and if the satellite system used for positioning is the Beidou+GPS system, the satellite number requirement is 24;

[0057] (305) If enough satellites cannot be obtained, the enhanced positioning fails.

[0058] Furthermore, in step 4, the correction information and the observation data are encoded using the RTCM 3.3 and its extended protocols. Among them, the satellite precise orbit correction, the satellite precise clock offset correction, the satellite code bias correction, the satellite phase bias correction, and the Beidou and GPS observation data are all transmitted using the RTCM 3.3 protocol, and the ionospheric delay correction and the tropospheric delay correction are transmitted using the RTCM3.3 extended protocol; the specific encoding is as follows:

[0059] If the preferred positioning mode is RTK and the satellite system is Beidou, the Beidou observation data of the reference base station and the coordinate information of the reference base station are encoded using types 1124 and 1005 in the RTCM 3.3 protocol;

[0060] If the preferred positioning mode is RTK and the satellite system is Beidou + GPS, the Beidou and GPS observation data of the reference base station are encoded using types 1124 and 1074 in the RTCM 3.3 protocol, and the coordinate information of the reference base station is encoded using type 1005;

[0061] If the preferred positioning mode is PPP-RTK, M1 is SPP, and the satellite system is Beidou, the Beidou satellite precise orbit, satellite precise clock offset, satellite code bias, and satellite phase bias are encoded using types 1258, 1259, 1260, and 1270 in the RTCM 3.3 protocol, and the ionospheric and tropospheric delay corrections are encoded using type 4001 based on the RTCM 3.3 extension; among them, type 4001 includes information type, seconds within a day, synchronization information, number of satellites, central latitude, central latitude, central geodetic height, tropospheric dry delay parameters 1-4, tropospheric wet delay parameters 1-5, and ionospheric parameter set;

[0062] If the preferred positioning mode is PPP-RTK, M1 is SPP, and the satellite system is Beidou + GPS, the Beidou satellite precise orbit, satellite precise clock offset, satellite code bias, and satellite phase bias are encoded using types 1258, 1259, 1260, and 1270 in the RTCM 3.3 protocol, the GPS satellite precise orbit, satellite precise clock offset, satellite code bias, and satellite phase bias are encoded using types 1057, 1058, 1059, and 1265 in the RTCM 3.3 protocol, and the ionospheric and tropospheric delay corrections are encoded using type 4001 based on the RTCM 3.3 extension;

[0063] If the preferred positioning mode is PPP-RTK, M1 is PPP, and the satellite system is Beidou, then the Beidou satellite phase deviation is encoded using type 1270 in the RTCM 3.3 protocol, and the ionospheric and tropospheric delay corrections are encoded using type 4001 extended from RTCM 3.3;

[0064] If the preferred positioning mode is PPP-RTK, M1 is PPP, and the satellite system is Beidou + GPS, then the Beidou and GPS satellite phase deviations are encoded using types 1270 and 1265 in the RTCM 3.3 protocol, and the ionospheric and tropospheric delay corrections are encoded using type 4001 extended from RTCM 3.3;

[0065] If the preferred positioning mode is PPP-AR, M1 is SPP, and the satellite system is Beidou, then the precise orbit of Beidou satellites, satellite precise clock error, satellite code deviation, and satellite phase deviation are encoded using types 1258, 1259, 1260, and 1270 in the RTCM 3.3 protocol;

[0066] If the preferred positioning mode is PPP-AR, M1 is SPP, and the satellite system is Beidou + GPS, then the precise orbit of Beidou satellites, satellite precise clock error, satellite code deviation, and satellite phase deviation are encoded using types 1258, 1259, 1260, and 1270 in the RTCM 3.3 protocol, and the precise orbit of GPS satellites, satellite precise clock error, satellite code deviation, and satellite phase deviation are encoded using types 1057, 1058, 1059, and 1265 in the RTCM 3.3 protocol;

[0067] If the preferred positioning mode is PPP-AR, M1 is PPP, and the satellite system is Beidou, then the Beidou satellite phase deviation is encoded using type 1270 in the RTCM 3.3 protocol;

[0068] If the preferred positioning mode is PPP-AR, M1 is PPP, and the satellite system is Beidou + GPS, then the Beidou and GPS satellite phase deviations are encoded using types 1270 and 1265 in the RTCM 3.3 protocol.

[0069] Further, the specific method of step 5 is as follows:

[0070] (501) When the positioning mode is RTK, based on the user's observation data, broadcast ephemeris, differential reference station corrections, and reference reference station coordinates, a double-difference processing method is used to establish the following corrected satellite model:

[0071]

[0072] In the formula, j and k are satellite identifiers, r is the user's position, b represents the ground monitoring station, and i represents the frequency; and respectively represent the phase and pseudorange observables after double-difference processing; represents the geometric distance after double-difference between the theoretical satellite and the receiver; λ i represents the wavelength; and respectively represent the ambiguities after double-difference of satellite j and satellite k; represents the residual phase correction information; ε Φ and ε P respectively represent the phase and pseudorange observation noises;

[0073] Then, the extended Kalman filtering method is used to fix the double-difference ambiguity and solve for the precise position of the user;

[0074] (502) When the positioning mode is PPP-AR, based on the user's observation data, broadcast ephemeris, and correction information, the following satellite correction model is used for calculation to construct a functional equation:

[0075]

[0076] and satisfy:

[0077]

[0078] In the formula, P IF and L IF respectively represent the pseudorange and carrier combined observables in the ionosphere-free combination, ρ is the geometric distance between the satellite and the ground, c is the speed of light, t r is the receiver clock error, t s is the satellite clock error, η is the tropospheric projection function, T is the tropospheric zenith delay, λ NL is the wavelength of the narrow-lane combined quantity, N WL is the ambiguity of the wide-lane combined quantity, α 12 , β 12 are both ionosphere-free combination coefficients; B r,f and b r,f respectively represent the code and phase biases of the receiver at frequency f, and respectively represent the code and phase biases of the satellite at frequency f; λ f and N f respectively represent the carrier wavelength and ambiguity at frequency f;

[0079] Then, the extended Kalman filtering method is used to fix the ambiguity and solve for the precise position of the user's station;

[0080] (503) When the positioning mode is PPP-RTK, first calculate the ionospheric and tropospheric delay corrections of the user according to the atmospheric correction calculation model. Among them, the dry tropospheric delay ZHD of the user's stationr and the wet delay ZWD r The calculation model is as follows:

[0081]

[0082] In the formula, represents the deviation of the user's station (b r , l r , h r ) from the central longitude B, and Δθ r represents the deviation of the user's station (b r , l r , h r ) from the central latitude L. The calculation method is as follows:

[0083]

[0084] Δθ = l r - L

[0085] When the deviation between the elevation h of the user's station and the central elevation H of the station is within 100 meters, the central elevation H is used instead; otherwise, h r is used as the actual value; r The calculation process of the ionospheric delay correction at the user's station is as follows:

[0086] The ionospheric delay correction at the user's station The calculation process is as follows:

[0087] Step 1: Calculate the ionospheric pierce point location based on the user's station position (b r , l r , h r ) and the satellite position (B s , L s , H s ) The ionospheric pierce point is the intersection point of the single ionospheric thin layer and the satellite - ground line of sight. The calculation method of the pierce point of the line of sight for each satellite - station is as follows:

[0088] (1) Based on the observation data collected by the user's station receiver and the broadcast ephemeris data, calculate the user's station position (b r , l r , h r ) and the satellite altitude angle azimuth angle

[0089] (2) Calculate the ionospheric pierce point latitude

[0090]

[0091] α = z - z'

[0092]

[0093] In the formula, R E is the radius of the earth, and H is the height h of the single ionospheric thin layer IPP , h IPP is a fixed value;

[0094] (3) Calculate the longitude θ of the ionospheric piercing point IPP :

[0095] When any one of the following two situations exists, calculate the longitude of the ionospheric piercing point according to Method 1, otherwise calculate the longitude of the ionospheric piercing point according to Method 2:

[0096] Situation 1: b r > 70° and

[0097] Situation 2: b r < -70° and

[0098] Method 1:

[0099]

[0100] Method 2:

[0101]

[0102] The second step: Calculate the ionospheric delay correction, and the calculation method is as follows:

[0103]

[0104] In the formula, and Δθ IPP = θ IPP -L respectively represent the differences between the longitude and latitude of the piercing point of the single ionospheric thin layer passed by the satellite to the user station and the central longitude and latitude (B, L) of the measurement area;

[0105] Then, calculate according to the following PPP-RTK satellite correction model and construct a functional equation:

[0106]

[0107] In the formula, is the satellite clock error correction for estimating the absorption troposphere and satellite code delay by the server, is the ionospheric error for estimating the absorption satellite without geometric code delay by the server, and are respectively the satellite code and phase delay errors of the absorption satellite without geometry and without ionospheric combined code delay estimated by the server at the j frequency point; is the receiver clock error parameter for the hardware delay of the absorption and reception end without ionosphere combination code to be estimated at the user side, and is the receiver geometric and conventional code delay correction parameter to be estimated at the user side, is the ambiguity parameter to be estimated after eliminating the reference frequency point and reference satellite, ε j and ζ j are the pseudorange and carrier observation noises at the j frequency point respectively;

[0108] Finally, the extended Kalman filtering method is used to fix the ambiguity and calculate the precise position of the user station.

[0109] The advantages of the present invention compared with the prior art methods are as follows:

[0110] (1) The present invention can realize the satellite-ground integrated multi-mode adaptive precise positioning service of RDSS / 5G fusion.

[0111] (2) The present invention designs a user precise position service request protocol, a precise positioning application service protocol and a service preference planning table, which can realize precise positioning services at different levels of RDSS and in different modes, and can meet the precise position service requirements in marine, desert and emergency rescue scenarios;

[0112] (3) The present invention supports the safe use of users (i.e., does not expose the user's position), and the coding supports custom expansion, which can support special security application requirements. Description of the Drawings

[0113] Figure 1 is the schematic diagram of the principle of the present invention.

[0114] Figure 2 is the flow chart of the present invention. Detailed Embodiments

[0115] The present invention will be further described below with reference to the drawings.

[0116] Such as Figure 1As shown in the figure, a method for enhanced adaptive precise positioning of an integrated space-ground system integrating RNSS / RDSS / 5G. First, the user-side receiver collects and receives raw satellite observation data, broadcast ephemeris and other information, and performs basic positioning. According to the designed request protocol, it reports information such as the user's location and service level requirements to the service center through the 5G network or RDSS communication. Secondly, the service center determines the positioning service mode by optimization based on preset parameters, monitoring station locations, and service requests. Then, according to the selected positioning mode, the service center selects satellites by combining parameters such as the satellite system and the cut-off elevation angle, and also combines the PDOP (Position Dilution of Precision) optimization strategy. In addition, according to the designed protocol, the service center transmits back the corrections of each satellite (orbit, clock error, code deviation, and phase deviation), atmospheric corrections (ionosphere and troposphere), differential corrections of the reference station, and reference coordinate information of the selected satellite system. Finally, the user side analyzes various corrections, calculates the correction amounts according to the model, and then performs adaptive precise positioning processing to obtain the precise positioning result on the user side.

[0117] As Figure 2 shown, the method includes the following steps:

[0118] Step 1: The user receives and analyzes the GNSS observation data and broadcast ephemeris information of the satellite system in real time, performs RNSS basic positioning, and determines the form of the request protocol according to the user type. The request protocol is divided into two types: the approximate position transmission protocol and the position coding protocol. Among them, the approximate position transmission protocol reports the user's approximate position, positioning mode, satellite system, and service level requirements to the service center in the form of request protocol information, and the position coding protocol reports the horizontal and elevation coding of the user's position, positioning mode, satellite system, and service level requirements to the service center in the form of request protocol information; the service level requirements are divided into three positioning requirements: PPP-AR, PPP-RTK, and RTK.

[0119] Step 2: The service center analyzes the request protocol, and selects the optimal positioning mode for enhanced positioning from PPP-AR, PPP-RTK, and RTK according to the distribution position information of ground monitoring stations, the satellite system, and the user request protocol information, and determines the correction information for enhanced positioning. The correction information is part or all of the satellite precise orbit correction, satellite precise clock error correction, satellite code deviation correction, satellite phase deviation correction, ionospheric delay correction, tropospheric delay correction, differential correction of the reference benchmark station, and reference benchmark station coordinate information.

[0120] Step 3: The service center performs satellite selection processing according to the selected positioning mode, combined with preset parameters, including parameters such as the satellite system and the satellite cut-off elevation angle, according to the designed optimization principle.

[0121] Step 4: The service center sends the positioning mode, correction information, and information on preferred satellites to the user in the form of a service agreement. Among them, the positioning mode is one of PPP-AR, PPP-RTK, and RTK, and the correction information is associated with the positioning mode;

[0122] Step 5: The user receives the service agreement, parses out the relevant correction information, corrects the satellite model according to the type of correction information in combination with the error model calculation method, and performs precise positioning based on the corrected satellite model.

[0123] Further, the specific implementation method of user-side positioning and request information transmission in step (1) is as follows:

[0124] (101) The user-side receiver receives the GNSS (supporting at least the Beidou satellite navigation system) satellite navigation signal, and parses out the observation data and broadcast ephemeris;

[0125] (102) The receiver performs positioning processing, and performs standard single-point positioning (SPP) or B2b-PPP positioning;

[0126] (103) Report the request information including the approximate position (including longitude, latitude, and altitude) or position code (horizontal code, elevation code), service level requirements, etc. of the user-side receiver through Beidou RDSS or 5G communication. Among them, 5G communication is preferentially selected through the information method. When 5G communication is not available, Beidou RDSS communication is selected.

[0127] The detailed request protocol format is as follows:

[0128] The request protocol uses an ASCII encoding structure to transmit the approximate position, position code, and service level requirement information, including two types: the approximate position transmission protocol and the position code protocol. The protocol content is as follows:

[0129] Approximate position transmission protocol:

[0130] $GNPOS,<1>,<2>,<3>,<4>,<5>,<6>,M,<7>,M,<8>,<9>,<10>*xx CR LF

[0131] In the protocol, <1>-<10> are defined as follows in the table. M represents meters, xx represents the exclusive OR checksum of all ASCII codes from $ to *, CR represents the carriage return character, and LF represents the line feed character. The content is as follows:

[0132] Table 1 GNPOS protocol content

[0133]

[0134] Position code protocol:

[0135] $GNPCD, <1>, <2>, <3>, <4>, <5>, <6> * xx CR LF

[0136] In the protocol, <1> - <6> are defined as follows in the table below. Other information is the same as the definition of $GNPOS, and the content is as follows:

[0137] Table 2 GNPCD Protocol Content

[0138]

[0139]

[0140] This protocol does not directly expose the user's approximate location (i.e., longitude, latitude, and altitude) information. The specific coding grid resolution (i.e., the grid horizontal range and elevation gradient interval) is designed by the user. It has higher security and privacy, and can be conveniently set by high-security users for their own use.

[0141] Furthermore, the specific method for preferably implementing the positioning mode in step (2) is as follows:

[0142] (201) If the user side reports using the approximate location transmission protocol:

[0143] First, convert the user side location (longitude, latitude, and altitude) to ECEF coordinates. Calculate the nearest monitoring station based on the distance between the user location coordinates and the coordinates of each monitoring station as follows:

[0144]

[0145] d min = min{d 1 , d 2 ... d k}

[0146] where (x 0 , y 0 , z 0 ) is the user's location in the ECEF coordinate system, (x k , y k , z k ) represents the coordinate positions of each monitoring station, and min{} represents obtaining the minimum value among all variables;

[0147] Then, according to the constraint planning table related to factors such as communication mode, positioning mode, and applicable range (as shown in the table below), select the positioning mode. The basic principles for selection include two points:

[0148] (1) Under the condition of supporting 5G, preferably use 5G communication. Under the condition of 5G communication, the communication volume in the constraint planning table can be satisfied;

[0149] (2) Under the condition of only RDSS communication, according to the used RDSS communication card, the positioning modes are preferably selected in descending order of positioning performance, where the positioning performance from high to low is: RTK > PPP-RTK > PPP-AR;

[0150] When SPP positioning is adopted on the user side, it is necessary to transmit satellite orbits, clock errors, code biases, and other required information from the service center to the user; when PPP positioning (specifically Beidou B2b-PPP) is adopted on the user side, it is no longer necessary to transmit the satellite orbits, clock errors, and code biases of both the Beidou and GPS systems, and only other information required for each positioning mode is transmitted.

[0151] Table 3 Preferred Constraint Planning Table for Positioning Modes

[0152]

[0153]

[0154] (1) The types of broadcast information are described as follows: 1 Satellite precise orbit correction; 2: Satellite precise clock error correction; 3: Satellite code bias correction; 4: Satellite phase bias correction; 5: Ionospheric delay correction; 6: Tropospheric delay correction; 7: Beidou observation data; 8: GPS observation data; 9: Coordinate information data of the reference base station. The communication bandwidth calculation is based on the RTCM protocol standard;

[0155] (2) Since the satellites will be selected according to the constraint conditions during the subsequent satellite optimization, here, temporarily, the communication volume is calculated based on 12 satellites in a single system, 24 satellites in a dual system, and dual-frequency point correction;

[0156] When using the RDSS communication method, the general communication frequency should not be lower than 30s, otherwise the positioning accuracy will decrease. The classification of RDSS communication cards is shown in the following table:

[0157] Table 4 Beidou-3 Short Message Smart Card Grade Table

[0158]

[0159] (202) If the user side reports using the approximate position transmission protocol:

[0160] According to the size of the coding grid resolution, the applicable positioning mode is selected. When the coding grid resolution is less than 30 km, combined with other requirements, it can be preferably selected from the three positioning modes; when the coding grid resolution is between 30 and 180 km, combined with other requirements, it can be preferably selected from the two positioning modes of PPP-AR and PPP-RTK; when the grid resolution is greater than 180 km, only the PPP-AR positioning mode can be selected. Other constraint conditions and selection criteria are the same as those described in (201).

[0161] Further, the satellite selection method in step (3) is as follows:

[0162] (301) According to the user's location and the satellite's location, calculate the elevation angle of each satellite, obtain the visible satellite information of the user at the current epoch. If there is only the user location encoding, calculate the visible satellite information of the center point;

[0163] The location encoding is a directional approximate location representation method designed according to specific requirements. The service center should understand its specific meaning. Therefore, the service center can calculate the location of its center point.

[0164] (302) According to the preset satellite system and the requirement of the satellite cut-off elevation angle (generally not less than 10°), select the qualified satellites;

[0165] (303) When there is a single Beidou requirement and the number of satellites is greater than 12 (or when there is a dual-system requirement of Beidou + GPS and the number of satellites is greater than 24), use PDOP for satellite screening, and sequentially eliminate the satellites with the smallest contribution to the system until the number of satellites meets the requirement.

[0166] Further, the implementation process of sending information according to the selected satellite system and satellite encoding in step (4) is as follows:

[0167] (401) The satellite orbit, clock error, code deviation, phase deviation correction, atmospheric correction information, and observation data are all encoded using the RTCM protocol. The RTCM data structure is as follows:

[0168]

[0169] (402) The satellite orbit, clock error, code deviation, phase deviation correction, and reference base station observation data and coordinate information are all transmitted using the standard RTCM 3.3 protocol. Therefore, it will not be described in detail here. The various information types are shown in the following table:

[0170] Table 5 Statistical Table of Each Information Type

[0171] Name Satellite System Information Type Remarks Satellite Orbit Correction 1 Beidou 1258 Satellite Orbit Correction 2 GPS 1057 Satellite Clock Error Correction 1 Beidou 1259 Satellite Clock Error Correction 2 GPS 1058 Satellite Code Bias Correction 1 Beidou 1260 Satellite Code Bias Correction 1 GPS 1059 Satellite Phase Bias Correction 1 Beidou 1270 Satellite Phase Bias Correction 2 GPS 1265 Observation Data 1 Beidou 1124 Observation Data 2 GPS 1074 Atmospheric Correction 1 / 4001 Reference Base Station / 1005

[0172] (403) The atmospheric correction information (including ionosphere and troposphere) is designed with protocol extension on the basis of the RTCM3.3 protocol. The detailed protocol design format is as follows:

[0173] Table 6 Protocol of Data Field of Atmospheric Correction Information

[0174]

[0175]

[0176] In the table, Ubit represents an unsigned number; bit represents a signed number. A first digit of 0 indicates positive, and a first digit of 1 indicates negative.

[0177] (404) Under the RDSS communication frequency condition, the satellite phase deviation update frequency is set to 10 s / time, and the update frequency of other information is set to 30 s / time;

[0178] Furthermore, the implementation process of step (5) adaptive precise positioning is as follows:

[0179] (501) When the positioning mode is RTK, double-difference processing is adopted, and the calculation method is as follows:

[0180]

[0181] In the formula, j, k, r, b, and i represent satellite i, satellite j, the user-side station position r, the reference station b, and frequency i in sequence; and represent the phase and pseudorange observables after double-difference processing; represents the geometric distance after double-difference between the theoretical satellite and the receiver; λ i represents the wavelength; and represent the ambiguity after double-difference of the corresponding satellite; represents the residual phase correction information; ε Φ and ε P represent the phase and pseudorange observation noises.

[0182] Then, the extended Kalman filtering method is used to fix the double-difference ambiguity and solve for the precise position of the user-side station.

[0183] (502) When the positioning mode is PPP-AR, its positioning processing method is as follows:

[0184]

[0185] In the formula, P IF and L IF are the ionosphere-free (IF) pseudorange and carrier combination observables respectively, ρ is the satellite-to-ground geometric distance, c is the speed of light, t r is the receiver clock error, t s is the satellite clock error, η is the tropospheric projection function, T is the tropospheric zenith delay, λ NL is the wavelength of the narrow-lane combination quantity, N WL is the ambiguity of the wide-lane combination quantity, α 12 , β 12 are both IF combination coefficients; B r,f and b r,fThey are the receiver code and phase deviation at the f frequency point respectively. and They are the satellite code and phase deviation at the f frequency point respectively; λ f and N f They are the carrier wavelength and ambiguity at the f frequency point respectively.

[0186]

[0187] Then, the extended Kalman filtering method is used to fix the ambiguity and calculate the precise position of the user-side station.

[0188] (503) When the positioning mode is PPP-RTK, the atmospheric correction calculation model is as follows:

[0189] The tropospheric dry delay (ZHD r ) and wet delay (ZWD r ) calculation models for the user-side station are:

[0190]

[0191] In the formula represents the deviation of the user-side station (b r , l r , h r ) from the central longitude B, and Δθ r represents the deviation of the user-side station (b r , l r , h r ) from the central latitude L. The calculation method is as follows:

[0192]

[0193] Δθ = l r - L

[0194] Note: When the deviation between the elevation h r of the user-side station and the central elevation H of the station is within 100 meters, the central elevation H is used instead; otherwise, the actual value of h r is used for the above calculation.

[0195] The ionospheric delay correction for the user-side station The calculation process is as follows:

[0196] The first step: Based on the position of the user-side station (b r , l r , h r ) and the satellite position (B s , L s , H s ) to calculate the piercing point position The ionospheric piercing point is a single ionospheric thin layer (h IPPis a fixed value, 350 km), and the position of the intersection point of the satellite-ground line of sight. The calculation method of the piercing point of the line of sight of each satellite measurement station is as follows:

[0197] ① Calculate the position of the user-side measurement station (b r , l r , h r ) and the satellite elevation angle azimuth angle

[0198] ② The latitude of the piercing point The calculation method is as follows:

[0199]

[0200] α = z - z'

[0201]

[0202] In the formula, R E is the radius of the earth, with a value of 6378.138 km; H is the height of the single ionospheric thin layer h IPP .

[0203] ③ The longitude of the piercing point θ IPP The calculation method is as follows:

[0204] When there are the following two situations, calculate the longitude of the piercing point according to Method 1, otherwise according to Method 2

[0205] Situation 1: b r > 70° and

[0206] Situation 2:

[0207] Method 1:

[0208]

[0209] Method 2:

[0210]

[0211] Second step: Calculate the ionospheric delay correction. The calculation method is as follows:

[0212]

[0213] In the formula and Δθ IPP = θ IPP - L respectively represent the differences between the longitude and latitude of the piercing point of the single ionospheric thin layer passed by the satellite to the user measurement station and the central longitude and latitude (B, L) of the measurement area.

[0214] (504) When the positioning mode is PPP-RTK, the phase deviation correction is the same as the method in step (602). The PPP-RTK processing model method is as follows:

[0215]

[0216] In the formula, is the satellite clock error correction for absorbing the troposphere and satellite code delay estimated by the server, is the ionospheric error for absorbing the satellite geometric-free code delay estimated by the server, and are respectively the satellite code and phase delay errors of the absorbing satellite geometric-free and ionosphere-free combined code delay estimated by the server at the j frequency point; is the receiver clock error parameter to be estimated by the user side for absorbing the hardware delay of the receiver IF combined code, and are the receiver geometric-free and conventional code delay correction parameters to be estimated by the user side, is the ambiguity parameter to be estimated after eliminating the reference frequency point and reference satellite, ε j and ζ j are respectively the pseudorange and carrier observation noises at the j frequency point.

[0217] Then, the extended Kalman filter method is used to fix the ambiguity and calculate the precise position of the user-side station.

[0218] In summary, the present invention effectively overcomes the situation where precise positioning cannot be achieved due to the influence of a single communication means, gives full play to the communication advantages of Beidou RDSS, realizes satellite-ground integrated adaptive precise positioning services in multiple modes, improves the positioning robustness and ensures high-precision characteristics, and can provide strong assistance for Beidou in major applications such as navigation, aviation, and desert operations.

Claims

1. A satellite-ground integrated enhanced adaptive precise positioning method for RNSS / RDSS / 5G fusion, characterized in that: The method is used to optimize the satellite system and satellite for the positioning method requested by the user through the service center, so that the user can achieve enhanced positioning effect with the assistance of the ground monitoring station. The user and the service center communicate in a 5G or RDSS manner. The service center forms various correction information required for user positioning based on all ground monitoring stations. The satellite system used for positioning is the Beidou system or the Beidou + GPS system. The method comprises the following steps: Step 1: The user receives and parses the GNSS observation data and broadcast ephemeris information of the satellite system in real time to perform RNSS basic positioning. The form of the request protocol is determined according to the user type. The request protocol is divided into two types: the rough position transmission protocol and the position coding protocol. The rough position transmission protocol reports the user's rough position, positioning mode, satellite system, and service level requirements to the service center in the form of request protocol information. The position coding protocol reports the user's horizontal and elevation coding, positioning mode, satellite system, and service level requirements to the service center in the form of request protocol information. The service level requirements are divided into three types of positioning requirements: PPP-AR, PPP-RTK, and RTK. Step 2: The service center parses the request protocol, selects the optimal positioning mode for enhanced positioning from PPP-AR, PPP-RTK, and RTK according to the distribution location information of the ground monitoring stations, the satellite system, and the user request protocol information, and determines the correction information for enhanced positioning, wherein the correction information is satellite precise orbit correction, satellite precise clock correction, satellite code deviation correction, satellite phase deviation correction, ionospheric delay correction, tropospheric delay correction, reference base station differential correction, and part or all of the reference base station coordinate information; Step 3: The service center selects the optimal satellite using the spatial position precision factor method based on the selected positioning mode and satellite cutoff altitude angle; Step 4: The service center sends the positioning mode, correction information, and information of the preferred satellite to the user in the form of a service agreement, wherein the positioning mode is one of PPP-AR, PPP-RTK, and RTK, and the correction information is associated with the positioning mode; Step 5: The user receives the service agreement, parses the relevant correction information, corrects the satellite model according to the correction information type and the error model calculation method, and performs precise positioning based on the corrected satellite model.

2. According to claim 1, a satellite-ground integrated enhanced adaptive precise positioning method for RNSS / RDSS / 5G fusion is characterized in that: 5G is used preferentially for communication between users and service centers. RDSS is used for communication only when 5G is not available.

3. The RNSS / RDSS / 5G fusion satellite-ground integrated enhanced adaptive precise positioning method according to claim 1 is characterized in that: The request protocol adopts an ASCII encoding structure, including two types: a rough location transmission protocol and a location encoding protocol; The rough position transmission protocol includes the following information: UTC time, latitude, latitude hemisphere, longitude, longitude hemisphere, altitude, geoid height anomaly difference, positioning mode, service level requirements, satellite system requirements, checksum; The position encoding protocol includes the following information: UTC time, horizontal code, elevation code, positioning mode, service level requirements, satellite system requirements, and check code; among them, the horizontal code is used to represent the horizontal area, and the elevation code is used to represent the elevation area.

4. The RNSS / RDSS / 5G fusion satellite-ground integrated enhanced adaptive precise positioning method according to claim 3 is characterized in that: If the user adopts the rough location transmission protocol, the specific method of step 2 is: (211) parsing the rough location transmission protocol to obtain information on latitude, longitude, and altitude; (212) converting the user location represented by latitude, longitude, and altitude into ECEF coordinates; (213) Calculate the distance from the user's location coordinates to each ground monitoring station, find the ground monitoring station closest to the user's location, and obtain the distance D1 between the user and the ground monitoring station; (214) According to the distance D1 between the user and the ground monitoring station and the positioning mode M2 ​​requested by the user, the optimal positioning mode for enhanced positioning is selected: When M2 is RTK, if D1 is greater than 180km, the PPP-AR positioning mode is selected; if D1 is greater than 30km and not greater than 180km, the PPP-RTK positioning mode is selected; if D1 is not greater than 30km, the RTK positioning mode is selected; When M2 is PPP-RTK, if D1 is greater than 180km, the PPP-AR positioning mode is used, otherwise the PPP-RTK positioning mode is used; When M2 is PPP-AR, the PPP-AR positioning mode is selected; (215) Select correction information for enhanced positioning based on the positioning mode M1 originally used by the user, the positioning system in the request protocol, and the selected optimal positioning mode: If M1 is SPP and PPP-AR mode is selected, the correction information is the satellite precise orbit, satellite precise clock error, satellite code deviation and satellite phase deviation, and the satellite system is the positioning system specified in the request protocol; If M1 is SPP and PPP-AR mode is selected, the correction information is the satellite phase deviation; If M1 is SPP and PPP-RTK mode is selected, the correction information includes satellite precise orbit, satellite precise clock error, satellite code deviation, satellite phase deviation, ionospheric and tropospheric delay correction; If M1 is PPP and PPP-RTK mode is selected, the correction information is satellite phase deviation, ionospheric and tropospheric delay correction; If the RTK mode is selected and the positioning system is Beidou, the correction information is Beidou observation data and reference base station coordinate information; If RTK mode is selected and the positioning system is Beidou + GPS, the correction information is Beidou, GPS observation data and reference base station coordinate information; If the user adopts the position coding protocol, the specific method of step 2 is: (221) The service center parses the position coding protocol, obtains the horizontal code and the elevation code, and calculates the center position of the area corresponding to the horizontal code and the elevation code, that is, the longitude, latitude and altitude information of the coding center; (222) Convert the longitude, latitude and altitude information of the encoding center into ECEF coordinates; (223) Calculate the distance from the coding center to each ground monitoring station, find the ground monitoring station closest to the coding center, and obtain the distance D1 between the coding center and the ground monitoring station; (224) According to the distance D1 between the encoding center and the ground monitoring station and the positioning mode M2 ​​requested by the user, the optimal positioning mode for enhanced positioning is selected: When M2 is RTK, if D1 is greater than 180km, the PPP-AR positioning mode is selected; if D1 is greater than 30km and not greater than 180km, the PPP-RTK positioning mode is selected; if D1 is not greater than 30km, the RTK positioning mode is selected; When M2 is PPP-RTK, if D1 is greater than 180km, the PPP-AR positioning mode is used, otherwise the PPP-RTK positioning mode is used; When M2 is PPP-AR, the PPP-AR positioning mode is selected; (225) Select correction information for enhanced positioning based on the positioning mode M1 originally used by the user, the positioning system in the request protocol, and the selected optimal positioning mode: If M1 is SPP and PPP-AR mode is selected, the correction information is the satellite precise orbit, satellite precise clock error, satellite code deviation and satellite phase deviation, and the satellite system is the positioning system specified in the request protocol; If M1 is SPP and PPP-AR mode is selected, the correction information is the satellite phase deviation; If M1 is SPP and PPP-RTK mode is selected, the correction information includes satellite precise orbit, satellite precise clock error, satellite code deviation, satellite phase deviation, ionospheric and tropospheric delay correction; If M1 is PPP and PPP-RTK mode is selected, the correction information is satellite phase deviation, ionospheric and tropospheric delay correction; If the RTK mode is selected and the positioning system is Beidou, the correction information is Beidou observation data and reference base station coordinate information; If the RTK mode is selected and the positioning system is Beidou + GPS, the correction information is Beidou, GPS observation data and reference base station coordinate information.

5. The RNSS / RDSS / 5G fusion satellite-ground integrated enhanced adaptive precise positioning method according to claim 4 is characterized in that: The specific method of step 3 is: (301) Based on the broadcast ephemeris of each ground monitoring station, the broadcast ephemeris of the entire constellation is obtained by merging the ephemeris, and then the positions of the visible satellites within the next 3 minutes are calculated based on the ephemeris; (302) Obtaining the position of the feature point, and then calculating the altitude angle of each satellite based on the position of the feature point and each satellite; If the request protocol sent back by the user adopts the approximate location transmission protocol, the characteristic point is the user's location, that is, the user's latitude, longitude and altitude; If the request protocol sent back by the user adopts the position coding protocol, the feature point is the position of the coding center, and the user obtains the position through the decoding book; (303) According to the preset satellite cut-off elevation angle requirement, all satellites meeting the requirement are screened out; (304) Using the spatial position precision factor method to screen the satellites that meet the requirements, and successively remove the satellites that contribute the least to positioning until the satellite number requirements are met; Among them, if the satellite system used for positioning is the Beidou system, the number of satellites required is 12; if the satellite system used for positioning is the Beidou + GPS system, the number of satellites required is 24; (305) If sufficient satellites cannot be obtained, enhanced positioning fails.

6. The RNSS / RDSS / 5G fusion satellite-ground integrated enhanced adaptive precise positioning method according to claim 5 is characterized in that: In step 4, the correction information and observation data are encoded using RTCM 3.3 and its extended protocol. Among them, satellite precise orbit correction, satellite precise clock correction, satellite code bias correction, satellite phase bias correction, and Beidou and GPS observation data are all transmitted using the RTCM 3.3 protocol, and ionospheric delay correction and tropospheric delay correction are transmitted using the RTCM3.3 extended protocol. The specific encoding is as follows: If the preferred positioning mode is RTK and the satellite system is BeiDou, the BeiDou observation data of the reference base station and the coordinate information of the reference base station are encoded using the 1124 and 1005 types in the RTCM 3.3 protocol; If the preferred positioning mode is RTK and the satellite system is Beidou + GPS, the Beidou and GPS observation data of the reference base station are encoded using the 1124 and 1074 types in the RTCM 3.3 protocol, and the reference base station coordinate information is encoded using the 1005 type; If the preferred positioning mode is PPP-RTK, M1 is SPP, and the satellite system is Beidou, the 1258, 1259, 1260, and 1270 types in the RTCM 3.3 protocol are used to encode the Beidou satellite precise orbit, satellite precise clock error, satellite code bias, and satellite phase bias, and the 4001 type based on the RTCM 3.3 extension is used to encode the ionospheric and tropospheric delay corrections; where the 4001 type includes information type, seconds per day, synchronization information, number of satellites, central latitude, central latitude, central geodetic height, tropospheric dry delay parameters 1-4, tropospheric wet delay parameters 1-5, and ionospheric parameter set; If the preferred positioning mode is PPP-RTK, M1 is SPP, and the satellite system is Beidou + GPS, the 1258, 1259, 1260, and 1270 types in the RTCM 3.3 protocol are used to encode the Beidou satellite precise orbit, satellite precise clock error, satellite code bias, and satellite phase bias. The 1057, 1058, 1059, and 1265 types in the RTCM 3.3 protocol are used to encode the GPS satellite precise orbit, satellite precise clock error, satellite code bias, and satellite phase bias. The 4001 type based on the RTCM 3.3 extension is used to encode the ionospheric and tropospheric delay corrections. If the preferred positioning mode is PPP-RTK, M1 is PPP, and the satellite system is Beidou, the 1270 type in the RTCM 3.3 protocol is used to encode the Beidou satellite phase deviation, and the 4001 type based on the RTCM 3.3 extension is used to encode the ionospheric and tropospheric delay corrections; If the preferred positioning mode is PPP-RTK, M1 is PPP, and the satellite system is Beidou + GPS, the 1270 and 1265 types in the RTCM 3.3 protocol are used to encode the Beidou and GPS satellite phase deviations, and the 4001 type based on the RTCM 3.3 extension is used to encode the ionospheric and tropospheric delay corrections; If the preferred positioning mode is PPP-AR, M1 is SPP, and the satellite system is Beidou, the 1258, 1259, 1260, and 1270 types in the RTCM 3.3 protocol are used to encode the Beidou satellite precise orbit, satellite precise clock error, satellite code bias, and satellite phase bias; If the preferred positioning mode is PPP-AR, M1 is SPP, and the satellite system is Beidou + GPS, the 1258, 1259, 1260, and 1270 types in the RTCM 3.3 protocol are used to encode the Beidou satellite precise orbit, satellite precise clock error, satellite code bias, and satellite phase bias. The 1057, 1058, 1059, and 1265 types in the RTCM 3.3 protocol are used to encode the GPS satellite precise orbit, satellite precise clock error, satellite code bias, and satellite phase bias. If the preferred positioning mode is PPP-AR, M1 is PPP, and the satellite system is Beidou, the 1270 type in the RTCM 3.3 protocol is used to encode the Beidou satellite phase deviation; If the preferred positioning mode is PPP-AR, M1 is PPP, and the satellite system is Beidou + GPS, the 1270 and 1265 types in the RTCM3.3 protocol are used to encode the phase deviations of Beidou and GPS satellites.

7. The RNSS / RDSS / 5G fusion satellite-ground integrated enhanced adaptive precise positioning method according to claim 6 is characterized in that: The specific method of step 5 is: (501) When the positioning mode is RTK, based on user observation data, broadcast ephemeris, differential base station correction and reference base station coordinates, double difference processing is adopted to establish the corrected satellite model as follows: Where j and k are satellite identifiers, r is the user location, b represents the ground monitoring station, and i represents the frequency; and Respectively represent the phase and pseudorange observations after double difference processing; represents the geometric distance between the theoretical satellite and the receiver after double difference; λ i Indicates wavelength; and They represent the double-difference ambiguities of satellite j and satellite k respectively; Represents the residual phase correction information; ε Φ and ε P denote the phase and pseudorange observation noise respectively; Then, the extended Kalman filter method is used to fix the double difference ambiguity and solve the user's precise position; (502) When the positioning mode is PPP-AR, based on user observation data, broadcast ephemeris and correction information, calculation is performed according to the following satellite correction model to construct a function equation: And satisfy: Where P IF and L IF are the pseudorange and carrier combined observations under the ionosphere-free combination, ρ is the satellite-ground geometric distance, c is the speed of light, t r is the receiver clock error, t s is the satellite clock error, η is the tropospheric projection function, T is the tropospheric zenith delay, λ NL is the wavelength of the narrow-lane combination, N WL is the ambiguity of the wide lane combination, α 12 , β 12 All are ionosphere-free combination coefficients; B r,f and b r,f are the receiver code and phase deviation at frequency f, and are the satellite code and phase deviation of frequency f respectively; f and N f are the carrier wavelength and ambiguity at frequency f respectively; Then, the extended Kalman filter method is used to fix the ambiguity and solve the precise position of the user station; (503) When the positioning mode is PPP-RTK, the user ionospheric and tropospheric delay corrections are first calculated according to the atmospheric correction calculation model, where the user station tropospheric dry delay ZHD r and wet delay ZWD r The calculation model is: In the formula, Indicates the user station (b r ,l r ,h r ) and the central longitude B, Δθ r Indicates the user station (b r ,l r ,h r ) and the central latitude L, calculated as follows: Δθ=l r -L When the user's station height h r When the deviation of the central height H of the measuring station is within 100 meters, use the central height H instead, otherwise use h r Actual value; User station ionospheric delay correction The calculation process is as follows: Step 1: Based on the user station location (b r ,l r ,h r ) and satellite position (B s ,L s ,H s ) Calculate the position of the ionospheric puncture point The ionospheric puncture point is the intersection of a single ionospheric thin layer and the satellite-to-ground line of sight. The calculation method of the line of sight puncture point of each satellite station is as follows: (1) Based on the observation data collected by the user station receiver and the broadcast ephemeris data, the user station position (b r ,l r ,h r ) and satellite altitude angle Azimuth (2) Calculate the latitude of the ionospheric puncture point α=zz' In the formula, R E is the radius of the earth, H is the height of the single ionosphere layer h IPP ,h IPP is a fixed value; (3) Calculate the longitude θ of the ionospheric puncture point IPP : When any of the following two situations exists, the longitude of the ionospheric piercing point is calculated according to method 1, otherwise the longitude of the ionospheric piercing point is calculated according to method 2: Case 1: b r >70° and Case 2: b r <-70° and Method 1: Method 2: Step 2: Calculate the ionospheric delay correction. The calculation method is as follows: In the formula, and Δθ IPP =θ IPP -L respectively represent the difference between the latitude and longitude of the single ionospheric thin layer puncture point from the satellite to the user station and the central longitude and latitude of the measurement area (B, L); Then, the calculation is performed according to the following PPP-RTK satellite correction model to construct the function equation: In the formula, is the satellite clock correction estimated by the server to absorb the tropospheric and satellite code delays, is the ionospheric error estimated by the server to absorb the satellite's non-geometric code delay, and are the satellite code and phase delay errors of the j-frequency point absorbing satellite without geometry and ionosphere combined code delay estimated by the server, respectively; is the receiver clock error parameter to be estimated at the user end to absorb the hardware delay of the ionosphere-free combined code at the receiving end, and are the receiver geometry-free and conventional code delay correction parameters to be estimated at the user end, is the ambiguity parameter to be estimated after eliminating the reference frequency and reference satellite, ε j and j are the j-frequency pseudorange and carrier observation noise respectively; Finally, the extended Kalman filter method is used to fix the ambiguity and solve the precise position of the user station.

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