A baseline positioning method based on multiple frequencies of Beidou

Abstract

The application provides a baseline positioning method based on Beidou multi-frequency, comprising the following steps: step one, data preprocessing is performed on satellite observation data and navigation messages obtained by a reference station and a mobile station at a current epoch; step two, it is judged whether the distance between the reference station and the mobile station is less than a distance threshold, if yes, step three is executed, otherwise, step four is executed; step three, differential positioning is performed, and according to whether ambiguity is fixed in the differential positioning, an ambiguity fixed solution is obtained, or a Beidou multi-frequency single-epoch constraint algorithm is used to constrain ambiguity to be fixed, so as to obtain an ambiguity fixed solution or a floating point solution; step five is executed; step four, a Beidou multi-frequency weak ionosphere algorithm is used for differential positioning, so as to obtain an ambiguity fixed solution or a floating point solution; step five is executed; step five, position and velocity information is obtained according to the ambiguity fixed solution or the floating point solution, and positioning is completed. The application can solve the technical problems of long navigation time and insufficient positioning accuracy in satellite navigation positioning in the prior art.

Description

Technical Field

[0001] This invention relates to the field of multi-frequency positioning calculation technology, and in particular to a baseline positioning method based on BeiDou multi-frequency positioning. Background Technology

[0002] The most commonly used method for high-precision satellite positioning is carrier differential positioning. The key technology in carrier differential positioning is the ambiguity fixing method. When the carrier is dynamic or obstructed, the efficiency of ambiguity fixing will be affected. When the baseline distance is long, the solution time will be greatly extended or even impossible to solve.

[0003] Major satellite navigation systems can broadcast observations at two or more frequencies. These observations can be combined to create new observations. When the wavelength of the new observation is long, it can effectively reduce ambiguity search time and even achieve single-epoch fixed ambiguity. Specific combinations can also significantly weaken or eliminate the effects of ionospheric delay, especially when the baseline length is long, where the advantages of ionospheric-free combinations become apparent. The emergence of multi-frequency observations has provided broader development space for satellite navigation and positioning. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] This invention provides a baseline positioning method based on BeiDou multi-frequency, which includes:

[0006] Step 1: Perform data preprocessing on the satellite observation data and navigation messages acquired by the current epoch reference station and rover station. Data preprocessing includes data gross error detection and cycle slip detection. If the data gross error detection is abnormal or a cycle slip occurs, the current data fails the detection and no calculation is performed at the current epoch; otherwise, proceed to Step 2.

[0007] Step 2: Perform pseudorange single-point positioning on the base station and the rover station to obtain the distance between the base station and the rover station. Determine whether the distance between the base station and the rover station is less than the distance threshold. If it is, proceed to step 3; otherwise, proceed to step 4.

[0008] Step 3: Initialize the ambiguity using the BeiDou multi-frequency single-epoch constraint algorithm at the initial moment, perform differential positioning, and determine whether the differential positioning ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, use the BeiDou multi-frequency single-epoch constraint algorithm to constrain the ambiguity to be fixed, and determine whether the ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, obtain the floating-point solution of the ambiguity.

[0009] Perform step five;

[0010] Step 4: Use the BeiDou multi-frequency weak ionospheric algorithm to perform differential positioning, and determine whether the differential positioning ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, obtain the floating-point ambiguity solution.

[0011] Perform step five;

[0012] Step 5: Obtain position and velocity information based on the fixed ambiguity solution or floating-point solution to complete the positioning.

[0013] Furthermore, data gross error detection uses code observations to detect pseudorange gross errors, and the judgment criteria for data gross error detection are as follows: in,

[0014] b sat,C1,P1 b represents the deviation between the satellite end code observation C1 and the code observation P1. rcv,C1,P1 b represents the deviation between the receiver-side code observation C1 and code observation P1. sat,P1,P2 b represents the deviation between satellite end code observations P1 and P2. rcv,P1,P2 S represents the deviation between the code observations P1 and P2 at the receiver; C1,P1 S is the time variable between code observations C1 and P1. P1,P2 Let d be the time variable between code observations P1 and P2. iono ε represents the residual error term of ionospheric delay, ξ represents the observation noise, and k1 represents the multipath effect; k1 represents the first judgment threshold, and k2 represents the second judgment threshold.

[0015] Furthermore, cycle slip detection specifically includes: acquiring the phase observation combination values ​​of two consecutive epochs respectively, determining whether the difference between the phase observation combination values ​​of the two consecutive epochs is less than the cycle slip threshold; if so, then no cycle slip has occurred in the two consecutive epochs; otherwise, a cycle slip has occurred in the two consecutive epochs.

[0016] Furthermore, the combined value of phase observations at any epoch is based on Obtain, ΔΦ i The difference between the combined carrier phase observations of the i-th satellite at two frequency points is... and These are the carrier phase observations at two frequency points of the satellite, where f1 and f2 are the first and second carrier frequencies of the dual-frequency satellite receiver, respectively. and These represent the integer ambiguity of the carrier phase at two frequency points of the satellite, where c is the speed of light, and V is the carrier phase ambiguity at two frequency points. e This represents the total number of electrons over the distance from the receiver to the satellite.

[0017] Furthermore, the pseudorange single-point positioning solution equation is as follows:

[0018] Among them, XJ Represents the X and Y components of the spatial coordinates of the J-th satellite. J Let Y and Z represent the spatial coordinates of the J-th satellite. J X represents the Z component of the spatial coordinates of the J-th satellite. U Represents the receiver's spatial coordinates X and Y components. U Represents the receiver's spatial coordinates Y component, Z component U ρ represents the Z component of the receiver's spatial coordinates. J The uncorrected smooth pseudorange of the J-th satellite is given, where c represents the speed of light, DLC represents the ionospheric delay of the satellite signal, and t... U This represents the difference between the local time of the satellite navigation and positioning device and the satellite time clock, where n represents the number of satellites involved in the positioning.

[0019] Furthermore, in step three, differential positioning uses a double-difference observation model to calculate the three-dimensional coordinates of the rover at each time point. The double-difference observation model is as follows: Where ▽Δ represents the double difference operator, r and s represent the difference satellite and the reference satellite, respectively, and b and m represent the rover station and the base station, respectively. This represents the difference between the carrier observations from differential satellite r to mobile station b and reference station m, and the difference between the carrier observations from reference satellite s to mobile station b and reference station m. λ represents the difference between the distances from the differential satellite r to the mobile station b and the reference station m, and the difference between the distances from the reference satellite s to the mobile station b and the reference station m, where λ represents the wavelength of the corresponding frequency carrier. This represents the difference between the ambiguity difference from differential satellite r to rover b and base station m, and the difference between the ambiguity difference from reference satellite s to rover b and base station m. This represents the difference between the tropospheric delay from differential satellite r to rover b and reference station m, and the difference between the tropospheric delay from reference satellite s to rover b and reference station m. This represents the difference between the ionospheric delay from differential satellite r to rover b and reference station m, and the difference between the ionospheric delay from reference satellite s to rover b and reference station m. This represents the difference between the carrier observation noise from differential satellite r to mobile station b and reference station m and the difference between the carrier observation noise from reference satellite s to mobile station b and reference station m.

[0020] Furthermore, the specific methods for fixing ambiguity using the BeiDou multi-frequency single-epoch constraint algorithm include:

[0021] 1) First, solve the first ultra-wide lane of BD using a geometry-free model;

[0022] 2) Solve for the second ultra-wide alley using a geometry-free model;

[0023] 3) Solve the ambiguity of the wide lane and the ambiguity of the fundamental frequency point B1I using the geometric correlation model.

[0024] Furthermore, the geometry-free model is based on Solve for the first super-wide alleyway of BD, N (1) The ambiguity of the first ultra-wide alleyway is represented by ▽Δ, which represents the double difference operator, and φ is the ambiguity of the first ultra-wide alleyway. (1) P represents the carrier phase observation of the first ultra-wide lane. (1) Let λ represent the pseudorange observation of the first ultra-wide alleyway. (1) Indicates the wavelength of the first ultrawide alley, [·] round This represents the floor operator.

[0025] Furthermore, the BeiDou multi-frequency weak ionospheric algorithm is based on Perform, where B is the design matrix, ΔX rb For three-dimensional coordinate components, The tropospheric delay factor for the mobile station. The tropospheric delay coefficient of the reference station is denoted by ▽Δ, which represents the double difference operator, and N is the tropospheric delay coefficient of the reference station. IR For carrier phase integer ambiguity under the weak ionospheric model, P IR For pseudorange observations of weak ionospheric assemblies, φ IR For the carrier phase observation of the weak ionospheric combination, ▽ΔT dry For tropospheric dry delay, ▽Δρ is the distance from the satellite to the receiver.

[0026] Furthermore, in step five, floating-point solutions of coordinate parameters and ambiguities are obtained for each epoch. The fixed solution of the weak ionospheric combined ambiguity is obtained using the least squares algorithm. Based on the weak ionospheric combined observation equation, the fixed solution of the coordinate parameters is obtained from the fixed solution of the weak ionospheric combined ambiguity.

[0027] This invention provides a baseline positioning method based on BeiDou multi-frequency positioning. This method selects between conventional differential positioning and differential positioning using the BeiDou multi-frequency weak ionospheric algorithm, depending on the distance between the base station and the rover. When ambiguity cannot be fixed in conventional differential positioning, the BeiDou multi-frequency single-epoch constraint algorithm is used to constrain and fix the ambiguity. Finally, position and velocity information are obtained from the fixed ambiguity solution or floating-point solution to complete the positioning. This baseline positioning method utilizes the unique multi-frequency information of the BeiDou satellite navigation system, accelerating the ambiguity fixing convergence time and improving positioning speed, accuracy, and reliability under different baseline lengths. Compared with existing technologies, this invention solves the technical problems of long navigation time and insufficient positioning accuracy in existing satellite navigation positioning technologies. Attached Figure Description

[0028] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0029] Figure 1 A flowchart illustrating a baseline positioning method based on BeiDou multi-frequency according to a specific embodiment of the present invention is shown. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] like Figure 1 As shown, a baseline positioning method based on BeiDou multi-frequency is provided according to a specific embodiment of the present invention. This baseline positioning method based on BeiDou multi-frequency includes:

[0034] Step 1: Perform data preprocessing on the satellite observation data and navigation messages acquired by the current epoch reference station and rover station. Data preprocessing includes data gross error detection and cycle slip detection. If the data gross error detection is abnormal or a cycle slip occurs, the current data fails the detection and no calculation is performed at the current epoch; otherwise, proceed to Step 2.

[0035] Step 2: Perform pseudorange single-point positioning on the base station and the rover station to obtain the distance between the base station and the rover station. Determine whether the distance between the base station and the rover station is less than the distance threshold. If it is, proceed to step 3; otherwise, proceed to step 4.

[0036] Step 3: Initialize the ambiguity using the BeiDou multi-frequency single-epoch constraint algorithm at the initial moment, perform differential positioning, and determine whether the differential positioning ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, use the BeiDou multi-frequency single-epoch constraint algorithm to constrain the ambiguity to be fixed, and determine whether the ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, obtain the floating-point solution of the ambiguity.

[0037] Perform step five;

[0038] Step 4: Use the BeiDou multi-frequency weak ionospheric algorithm to perform differential positioning, and determine whether the differential positioning ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, obtain the floating-point ambiguity solution.

[0039] Perform step five;

[0040] Step 5: Obtain position and velocity information based on the fixed ambiguity solution or floating-point solution to complete the positioning.

[0041] This configuration provides a baseline positioning method based on BeiDou multi-frequency positioning. This method selects between conventional differential positioning and differential positioning using the BeiDou multi-frequency weak ionospheric algorithm, depending on the distance between the base station and the rover. When ambiguity cannot be fixed in conventional differential positioning, the BeiDou multi-frequency single-epoch constraint algorithm is used to constrain and fix the ambiguity. Finally, position and velocity information are obtained from the fixed ambiguity solution or floating-point solution to complete the positioning. This baseline positioning method utilizes the unique multi-frequency information of the BeiDou satellite navigation system, accelerating the ambiguity fixing convergence time and improving positioning speed, accuracy, and reliability under different baseline lengths.

[0042] Furthermore, in this invention, step one is first performed to preprocess the satellite observation data and navigation messages acquired by the current epoch reference station and the rover station. The data preprocessing includes data gross error detection and cycle slip detection. If the data gross error detection is abnormal or a cycle slip occurs, the current data fails the detection and no calculation is performed at the current epoch; otherwise, step two is performed.

[0043] As a specific embodiment of the present invention, data gross error detection uses code observations to detect pseudorange gross errors. The judgment criteria for data gross error detection are as follows: in, b sat,C1,P1 b represents the deviation between the satellite end code observation C1 and the code observation P1. rcv,C1,P1 b represents the deviation between the receiver-side code observation C1 and code observation P1. sat,P1,P2 b represents the deviation between satellite end code observations P1 and P2. rcv,P1,P2 S represents the deviation between the code observations P1 and P2 at the receiver; C1,P1 S is the time variable between code observations C1 and P1. P1,P2 Let d be the time variable between code observations P1 and P2. iono ε is the residual error term of ionospheric delay, ξ is the observation noise, and ξ is the multipath effect; k1 is the first judgment threshold and k2 is the second judgment threshold. Usually, k1 is taken as 10-30 meters and k2 is taken as 30-60 meters.

[0044] As another specific embodiment of the present invention, cycle slip detection specifically includes:

[0045] The phase observation combination values ​​of two consecutive epochs are obtained respectively. It is determined whether the difference between the phase observation combination values ​​of the two consecutive epochs is less than the cycle slip threshold. If it is, then there is no cycle slip in the two consecutive epochs; otherwise, there is a cycle slip in the two consecutive epochs.

[0046] Among them, the phase observation combination value of any epoch is based on Obtain, ΔΦ i The difference between the combined carrier phase observations of the i-th satellite at two frequency points is... and These are the carrier phase observations at two frequency points of the satellite, where f1 and f2 are the first and second carrier frequencies of the dual-frequency satellite receiver, respectively. and These represent the integer ambiguity of the carrier phase at two frequency points of the satellite, where c is the speed of light, and V is the carrier phase ambiguity at two frequency points. e This represents the total number of electrons over the distance from the receiver to the satellite.

[0047] In the above formula, only the ambiguity term and the ionospheric residual term remain. The small size of the ionospheric residual allows for the detection of cycle slips. If no cycle slip exists (i.e., the ambiguity of two epochs is the same), the difference between the combined phase observation values ​​of two consecutive epochs should be less than the cycle slip threshold. Conversely, if the difference is greater than this threshold, a cycle slip is considered to have occurred. In this invention, the cycle slip threshold can be set to 0.5.

[0048] Furthermore, in this invention, after the current data passes the detection, step two is executed: pseudorange single-point positioning is performed on the base station and the rover station to obtain the distance between the base station and the rover station, and it is determined whether the distance between the base station and the rover station is less than the distance threshold. If it is, step three is executed; otherwise, step four is executed.

[0049] As a specific embodiment of the present invention, the pseudorange single-point positioning solution equation is as follows:

[0050] Among them, X J Represents the X and Y components of the spatial coordinates of the J-th satellite. J Let Y and Z represent the spatial coordinates of the J-th satellite. J X represents the Z component of the spatial coordinates of the J-th satellite. U Represents the receiver's spatial coordinates X and Y components. U Represents the receiver's spatial coordinates Y component, Z component U ρ represents the Z component of the receiver's spatial coordinates. J Let represent the uncorrected smooth pseudorange of the J-th satellite, c represent the speed of light (299,792,458.0), DLC represent the ionospheric delay of the satellite signal, and t U This represents the difference between the local time of the satellite navigation and positioning device and the satellite time clock, where n represents the number of satellites involved in the positioning.

[0051] Furthermore, in this invention, when the distance between the base station and the rover is less than a distance threshold, step three is executed: at the initial moment, the ambiguity is initialized using the BeiDou multi-frequency single-epoch constraint algorithm, differential positioning is performed, and it is determined whether the differential positioning ambiguity is fixed. If so, a fixed ambiguity solution is obtained; otherwise, the ambiguity is constrained to be fixed using the BeiDou multi-frequency single-epoch constraint algorithm, and it is determined whether the ambiguity is fixed. If so, a fixed ambiguity solution is obtained; otherwise, a floating-point solution of the ambiguity is obtained.

[0052] As a specific embodiment of the present invention, differential positioning utilizes a double-difference observation model to calculate the three-dimensional coordinates of the rover station at each time point. The double-difference observation model is as follows: Where ▽Δ represents the double difference operator, r and s represent the difference satellite and the reference satellite, respectively, and b and m represent the rover station and the base station, respectively. This represents the difference between the carrier observations from differential satellite r to mobile station b and reference station m, and the difference between the carrier observations from reference satellite s to mobile station b and reference station m. λ represents the difference between the distances from the differential satellite r to the mobile station b and the reference station m, and the difference between the distances from the reference satellite s to the mobile station b and the reference station m, where λ represents the wavelength of the corresponding frequency carrier. This represents the difference between the ambiguity difference from differential satellite r to rover b and base station m, and the difference between the ambiguity difference from reference satellite s to rover b and base station m. This represents the difference between the tropospheric delay from differential satellite r to rover b and reference station m, and the difference between the tropospheric delay from reference satellite s to rover b and reference station m. This represents the difference between the ionospheric delay from differential satellite r to rover b and reference station m, and the difference between the ionospheric delay from reference satellite s to rover b and reference station m. This represents the difference between the carrier observation noise from differential satellite r to mobile station b and reference station m and the difference between the carrier observation noise from reference satellite s to mobile station b and reference station m.

[0053] In this invention, after determining the three-dimensional coordinates of the base station and the rover receiver, the distance between them can be calculated.

[0054] Typically, double-difference models require multiple epochs to obtain a solution with fixed ambiguity. This invention utilizes the BeiDou multi-frequency single-epoch constraint algorithm to constrain ambiguity fixation, specifically including:

[0055] 1) First, the first ultrawide lane (EWL1) of BD is solved using a geometry-free model.

[0056] 2) Solving the second ultrawide lane (EWL2) using a geometry-free model; In this invention, since the baseline length is less than 20km, the second ultrawide lane (EWL2) can also be solved using a geometry-free model.

[0057] 3) Solve for the ambiguity of the wide lane (WL1) and the ambiguity of the fundamental frequency point B1I using the geometric correlation model.

[0058] Among them, the method without a geometric model is the direct rounding method, i.e. N (1) The ambiguity of the first ultra-wide alleyway is represented by ▽Δ, which represents the double difference operator, and φ is the ambiguity of the first ultra-wide alleyway. (1) P represents the carrier phase observation of the first ultra-wide lane. (1) Let λ represent the pseudorange observation of the first ultra-wide alleyway. (1) Indicates the wavelength of the first ultrawide alley, [·] round This represents the floor operator.

[0059] The geometrically relevant model, represented by the least squares method, can be simplified to V = BX + L, where B is the design matrix of the equation, X represents the unknown parameters, and L is a constant term. When the number of simultaneously observed satellites is 4, a unique solution for the unknown parameters can be obtained: X = B -1 L. When the number of satellites observed simultaneously is greater than 4, according to the least squares principle, X = (B T B) -1 B T L.

[0060] Furthermore, in this invention, when the distance between the base station and the mobile station is not less than the distance threshold, step four is executed: differential positioning is performed using the BeiDou multi-frequency weak ionosphere algorithm to determine whether the differential positioning ambiguity is fixed. If so, a fixed ambiguity solution is obtained; otherwise, a floating-point ambiguity solution is obtained.

[0061] As a specific embodiment of the present invention, the BeiDou multi-frequency weak ionospheric algorithm is based on... Perform, where B is the design matrix, ΔX rb For three-dimensional coordinate components, The tropospheric delay factor for the mobile station. The tropospheric delay coefficient of the reference station is denoted by ▽Δ, which represents the double difference operator, and N is the tropospheric delay coefficient of the reference station. IR For carrier phase integer ambiguity under the weak ionospheric model, P IR For pseudorange observations of weak ionospheric assemblies, φ IR For the carrier phase observation of the weak ionospheric combination, ▽ΔT dry For tropospheric dry delay, ▽Δρ is the distance from the satellite to the receiver.

[0062] Furthermore, in this invention, after performing step three or step four to obtain the fixed ambiguity solution or floating-point solution, the position and velocity information are obtained based on the fixed ambiguity solution or floating-point solution to complete the positioning.

[0063] As a specific embodiment of the present invention, after obtaining the floating-point solution of the ambiguity in step four, the coordinate parameters and the floating-point solution of the ambiguity are obtained according to each epoch. The fixed solution of the weak ionospheric combination ambiguity is obtained by using the least squares algorithm. Based on the weak ionospheric combination observation equation, the fixed solution of the coordinate parameters is obtained according to the fixed solution of the weak ionospheric combination ambiguity.

[0064] Compared to the traditional three-step method, this invention can directly fix the combined ambiguity of the weak ionosphere without waiting for the wide aisle ambiguity to be fixed, and there is no need to restore the basic ambiguity, thus reducing the amount of data processing and operation steps.

[0065] This invention addresses the problems of long ambiguity convergence time after satellite signal loss in high dynamic and severe obstruction situations, and the difficulty in fixing ambiguity under long baseline conditions. It proposes a baseline positioning method based on BeiDou multi-frequency information. By using the multi-frequency information unique to the BeiDou satellite navigation system, the invention conducts research on multi-frequency baseline positioning solution methods, overcomes the bottleneck of slow ambiguity convergence time, accelerates the ambiguity fixing convergence time, and improves positioning speed, positioning accuracy, and positioning reliability under different baseline lengths.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A baseline positioning method based on Beidou multi-frequency, characterized in that, The baseline positioning method based on BeiDou multi-frequency includes: Step 1: Perform data preprocessing on the satellite observation data and navigation messages acquired by the current epoch reference station and rover station. The data preprocessing includes data gross error detection and cycle slip detection. If the data gross error detection is abnormal or a cycle slip occurs, the current data fails the detection and no calculation is performed at the current epoch; otherwise, proceed to Step 2. Step 2: Perform pseudorange single-point positioning on the base station and the rover station to obtain the distance between the base station and the rover station. Determine whether the distance between the base station and the rover station is less than the distance threshold. If it is, proceed to step 3; otherwise, proceed to step 4. Step 3: Initialize the ambiguity using the BeiDou multi-frequency single-epoch constraint algorithm at the initial moment, perform differential positioning, and determine whether the differential positioning ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, use the BeiDou multi-frequency single-epoch constraint algorithm to constrain the ambiguity to be fixed, and determine whether the ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, obtain the floating-point solution of the ambiguity. Perform step five; Step 4: Use the BeiDou multi-frequency weak ionospheric algorithm to perform differential positioning, and determine whether the differential positioning ambiguity is fixed. If so, obtain the fixed ambiguity solution; otherwise, obtain the floating-point ambiguity solution. Perform step five; Step 5: Obtain position and velocity information based on the fixed ambiguity solution or floating-point solution to complete the positioning.

2. The baseline positioning method based on BeiDou multi-frequency as described in claim 1, characterized in that, The data gross error detection adopts code observation value to detect pseudorange gross error, and the judgment standard of the data gross error detection is wherein, b sat,C1,P1 b is the bias of the satellite-end code observation C1 and the code observation P1 rcv,C1,P1 b is the bias of the receiver-end code observation C1 and the code observation P1 sat,P1,P2 b is the bias of the satellite-end code observation P1 and the code observation P2 rcv,P1,P2 b is the bias of the receiver-end code observation P1 and the code observation P2 C1,P1 S is the time-varying quantity between the code observations C1 and P1 P1,P2 d is the time-varying quantity between the code observations P1 and P2 iono ε is the ionospheric delay residual error term, ξ is the observation noise, and ξ is the multipath effect; k1 is the first judgment threshold, and k2 is the second judgment threshold.

3. The method according to claim 1, wherein, The cycle slip detection specifically includes: acquiring the phase observation combination value of two consecutive epochs respectively, determining whether the difference between the phase observation combination values ​​of the two consecutive epochs is less than the cycle slip threshold; if so, then no cycle slip has occurred in the two consecutive epochs; otherwise, a cycle slip has occurred in the two consecutive epochs.

4. The baseline positioning method based on BeiDou multi-frequency as described in claim 3, characterized in that, The phase observation combination value of any epoch is according to obtained, ΔΦ i is the difference of the carrier phase combination observation values of the two frequency points of the i th satellite, and respectively are the carrier phase observation values of the two frequency points of the satellite, f1 and f2 respectively are the first carrier frequency and the second carrier frequency of the dual-frequency satellite receiver, and respectively are the integer ambiguity of the carrier phase of the two frequency points of the satellite, c is the speed of light, V e is the total amount of electrons in the distance from the receiver to the satellite.

5. The multi-frequency BDS-based baseline positioning method according to claim 1, wherein, The pseudorange single-point positioning solution equation is: Among them, X J Represents the X and Y components of the spatial coordinates of the J-th satellite. J Let Y and Z represent the spatial coordinates of the J-th satellite. J X represents the Z component of the spatial coordinates of the J-th satellite. U Represents the receiver's spatial coordinates X and Y components. U Represents the receiver's spatial coordinates Y component, Z component U ρ represents the Z component of the receiver's spatial coordinates. J The uncorrected smooth pseudorange of the J-th satellite is given, where c represents the speed of light, DLC represents the ionospheric delay of the satellite signal, and t... U This represents the difference between the local time of the satellite navigation and positioning device and the satellite time clock, where n represents the number of satellites involved in the positioning.

6. The baseline positioning method based on BeiDou multi-frequency as described in claim 1, characterized in that, In step three, differential positioning uses a double-difference observation model to calculate the three-dimensional coordinates of the rover at each time point. The double-difference observation model is... in, This represents the double-difference operator, where r and s represent the difference satellite and the reference satellite, respectively, and b and m represent the rover station and the base station, respectively. This represents the difference between the carrier observations from differential satellite r to mobile station b and reference station m, and the difference between the carrier observations from reference satellite s to mobile station b and reference station m. λ represents the difference between the distances from the differential satellite r to the mobile station b and the reference station m, and the difference between the distances from the reference satellite s to the mobile station b and the reference station m, where λ represents the wavelength of the corresponding frequency carrier. This represents the difference between the ambiguity difference from differential satellite r to rover b and base station m, and the difference between the ambiguity difference from reference satellite s to rover b and base station m. This represents the difference between the tropospheric delay from differential satellite r to rover b and reference station m, and the difference between the tropospheric delay from reference satellite s to rover b and reference station m. This represents the difference between the ionospheric delay from differential satellite r to rover b and reference station m, and the difference between the ionospheric delay from reference satellite s to rover b and reference station m. This represents the difference between the carrier observation noise from differential satellite r to mobile station b and reference station m and the difference between the carrier observation noise from reference satellite s to mobile station b and reference station m.

7. The baseline positioning method based on BeiDou multi-frequency as described in claim 1, characterized in that, The specific methods for fixing ambiguity using the BeiDou multi-frequency single-epoch constraint algorithm include: 1) First, solve the first ultra-wide lane of BD using a geometry-free model; 2) Solve for the second ultra-wide alley using a geometry-free model; 3) Solve the ambiguity of the wide lane and the ambiguity of the fundamental frequency point B1I using the geometric correlation model.

8. The baseline positioning method based on BeiDou multi-frequency as described in claim 7, characterized in that, No geometric model based on Solve for the first super-wide alleyway of BD, N (1) The ambiguity of the first ultra-wide alleyway is represented by ▽Δ, which represents the double difference operator, and φ is the ambiguity of the first ultra-wide alleyway. (1) P represents the carrier phase observation of the first ultra-wide lane. (1) Let λ represent the pseudorange observation of the first ultra-wide alleyway. (1) Indicates the wavelength of the first ultrawide alley, [·] round This represents the floor operator.

9. The baseline positioning method based on BeiDou multi-frequency according to any one of claims 1 to 8, characterized in that, BeiDou multi-frequency weak ionospheric algorithm based on Perform, where B is the design matrix, ΔX rb For three-dimensional coordinate components, The tropospheric delay factor for the mobile station. The tropospheric delay factor for the base station. N represents the double difference operator. IR For carrier phase integer ambiguity under the weak ionospheric model, P IR For pseudorange observations of weak ionospheric assemblies, φ IR For carrier phase observations of weak ionospheric assemblies, For tropospheric dry delay, This represents the distance from the satellite to the receiver.

10. The baseline positioning method based on BeiDou multi-frequency according to any one of claims 1 to 9, characterized in that, In step five, floating-point solutions for coordinate parameters and ambiguities are obtained for each epoch. The fixed solution for the combined ambiguity of the weak ionosphere is obtained using the least squares algorithm. Based on the combined observation equation of the weak ionosphere, the fixed solution for the coordinate parameters is obtained from the fixed solution for the combined ambiguity of the weak ionosphere.

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