A BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction

Abstract

The application provides a BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction, which comprises the following steps: obtaining an original observation data file, a satellite broadcast ephemeris file and a differential code bias correction file; performing smoothing filtering inspection and gross error elimination processing on the original observation data to obtain processed satellite observation values; performing three-frequency ionosphere elimination combination on the Beidou B1I / B2a / B3I and B1C / B2a / B3I satellite observation values, and performing three-frequency differential code bias correction to obtain modified three-frequency combined observation values; calculating satellite clock difference correction, troposphere error correction, earth rotation correction and relativistic effect correction; using various error correction values and the modified three-frequency combined observation values to construct a three-frequency ionosphere-eliminated combined pseudorange observation equation, and then obtaining a user final spatial rectangular coordinate system positioning result, so that the multi-frequency pseudorange single-point positioning precision of the user end is improved.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation, and specifically relates to a BDS-3 three-frequency pseudorange single-point positioning method based on Differential Code Bias (DCB) correction. Background Technology

[0002] On June 23, 2020, with the successful launch of the last BeiDou-3 networking satellite into its predetermined orbit, the deployment of the BeiDou-3 global satellite navigation system constellation was fully completed. BeiDou-3 satellites not only inherited the frequencies of BeiDou-2 satellites but also added new frequencies, B1C and B2a, which are compatible with GPS and Galileo systems. The increased availability of satellites and richer frequency resources in BeiDou-3 has brought new development opportunities for navigation and positioning. While multi-frequency, multi-channel signals provide more combined observations, they also generate a series of new errors that urgently need to be addressed, with differential code error being one of them. Differential code error, as a significant error, can affect the pseudorange single-point positioning accuracy of the new frequencies B1C and B2a of the BeiDou satellite navigation system, and currently there is no effective method to correct this error. Summary of the Invention

[0003] The purpose of this invention is to provide a BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction. This method fully utilizes the advantages of multiple frequencies of the BeiDou-3 satellites and uses the DCB correction file released by the Data Analysis Center of the Chinese Academy of Sciences to correct the code deviation of the observation values ​​of the new frequencies B1C and B2a of BeiDou-3, thereby improving the accuracy of multi-frequency pseudorange single-point positioning at the user end.

[0004] The technical solution to achieve the purpose of this invention is as follows:

[0005] A BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction includes the following steps:

[0006] S1. Obtain the raw observation data file, satellite broadcast ephemeris file, and differential code bias correction file;

[0007] S2. Perform smoothing filtering and gross error removal on the raw observation data to obtain the processed satellite observation values;

[0008] S3. Combine the observations from BeiDou B1I / B2a / B3I and B1C / B2a / B3I satellites with three frequencies to eliminate ionospheric interference, and correct the combined observations with three-frequency differential code bias to obtain the corrected three-frequency combined observations.

[0009] S4. Calculate satellite clock error correction, tropospheric error correction, Earth rotation correction, and relativistic effect correction based on the empirical error processing model;

[0010] S5. Using the error correction value and the corrected three-frequency combined observation value, construct the three-frequency deionization ionospheric combined pseudorange observation equation, and then use the least squares parameter estimation to obtain the user's final XYZ positioning result in the spatial rectangular coordinate system.

[0011] The significant advantages of this invention compared to existing technologies are:

[0012] This invention proposes a BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction. It makes full use of the advantages of multiple frequency points of Beidou-3 satellites and uses the DCB correction file released by the Data Analysis Center of the Chinese Academy of Sciences to correct the code deviation of the observation values ​​of the new frequency points B1C and B2a of Beidou-3, thereby improving the accuracy of multi-frequency pseudorange single-point positioning at the user end. Attached Figure Description

[0013] Figure 1 This is a system block diagram used in the present invention.

[0014] Figure 2 This is a pseudorange single-point positioning error diagram of the B1I / B2a / B3I three-frequency deionization layer combination in this invention.

[0015] Figure 3 This is a pseudorange single-point positioning error diagram of the B1C / B2a / B3I three-frequency deionization layer combination in this invention. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0017] Combination Figure 1 This embodiment of a BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction includes the following steps:

[0018] S1. Obtain the raw observation data files, satellite broadcast ephemeris files, and differential code bias (DCB) correction files from the IGS (International GNSS Service) website;

[0019] S2. Perform smoothing filtering and gross error removal on the raw observation data to obtain the processed satellite observation values;

[0020] S3. Perform three-frequency deionization combination on the observation values ​​of BeiDou B1I / B2a / B3I and B1C / B2a / B3I satellites, and perform three-frequency differential code deviation correction on the combined observation values;

[0021] In this step, the BDS-3 three-frequency deionization combination observation values ​​and the three-frequency differential code deviation correction formula obtained by the present invention are explained in detail.

[0022] Let the pseudorange observations of the three BeiDou frequency points (B1, B2, B3) be denoted as P1, P2, and P3, respectively. Let the combination coefficients of the pseudorange observations of the three frequency points be denoted as α1, α2, and α3, respectively, and let the frequencies of the pseudorange observations of the three frequency points be denoted as f1, f2, and f3, respectively. Then the combined observations of the three BeiDou frequency ionospheric de-oscillation... It can be represented as:

[0023]

[0024] use The following three conditions must be met to construct the observation equation: ① The sum of the geometric distance coefficients of the observations must be constant at 1; ② The combined observations can eliminate the influence of first-order ionospheric errors; ③ The smaller the noise figure of the combined observations, the better.

[0025] The above requirements can be simplified as follows:

[0026]

[0027] Wherein, TEC represents the total number of electrons contained in a column that runs through the entire ionosphere along the signal propagation path when the base area is one unit area. This represents the total ionospheric delay, with MIN indicating the minimum value.

[0028] set up:

[0029]

[0030] Where f0 = 10.23MHz, and k1, k2, and k3 are the coefficients of the pseudorange observation frequencies at the three frequency points.

[0031] Will Substituting into equation (2), and using the function extremum method, the unique combination coefficient of the three-frequency deionization combination can be solved as follows:

[0032]

[0033] Based on the BeiDou-3 satellite signal frequency, the BDS-3 three-frequency de-ionospheric pseudorange combination coefficient can be obtained according to formula (4):

[0034] Table 1

[0035] BDS-3 signal combination <![CDATA[α1]]> <![CDATA[α2]]> <![CDATA[α3]]> B1I / B2a / B3I 2.343297280935860 -1.253989430020260 -0.089307850915598 B1C / B2a / B3I 2.290270070136270 -1.196463419509900 -0.093806650626362

[0036] Based on the values ​​in Table 1, the noise figure of the pseudorange observations for the BDS-3 three-frequency de-ionization combination is shown in Table 2. Compared with the two-frequency combination, the noise figure of the three-frequency de-ionization combination is reduced by approximately 24%.

[0037] Table 2

[0038]

[0039] The satellite clock bias reference for BDS broadcast ephemeris is B3I. The clock bias of each satellite calculated using the broadcast ephemeris actually includes the hardware delay of the reference frequency at the satellite end, that is:

[0040] t b,s =t s +d u,s (5)

[0041] Among them, t b,s To calculate the satellite clock bias using broadcast ephemeris parameters, t s To calculate the satellite clock bias using the satellite clock bias coefficient, d u,s This refers to the hardware delay of the observation value u at the satellite end.

[0042] Therefore, the pseudorange observation equations for the three frequencies of BeiDou B1, B2, and B3 can be expressed as:

[0043]

[0044] In the formula, r represents the receiver, s represents the satellite, P represents the pseudorange observation, ρ represents the distance from the satellite to the receiver, c represents the speed of light, and dt r dt represents the receiver clock bias. s d represents satellite clock bias. trop Indicates tropospheric error. This indicates code deviation correction at frequency B1. This indicates code deviation correction at frequency B2.

[0045] use The three-frequency non-ionospheric combined observation model can be obtained as follows:

[0046]

[0047] In equation (7),

[0048] This indicates the differential code deviation correction for the three-frequency combination, as shown in equation (2). The pseudorange observation equation for the three-frequency deionization sphere combination can be expressed as:

[0049]

[0050] Differential code bias is a hardware error that must be subtracted by the Global Navigation Satellite System (GNSS) data precision processing center. The DCB product used in this invention was released by the Chinese Academy of Sciences (CAS), and it supports observation data from the new frequency points B1C and B2a of MGEX and iGMAX. Detailed types of DCB for the BDS satellite navigation system provided by the CAS Data Analysis Center are shown in Table 3.

[0051] Table 3

[0052]

[0053] Among them, C2I corresponds to the B1I frequency point of the BeiDou system; C6I corresponds to the B3I frequency point of the BeiDou system; C1P, C1D, and C1X correspond to the new B1C frequency point of the BeiDou system; and C5P, C5D, and C5X correspond to the new B2a frequency point of the BeiDou system.

[0054] In equation (8) These correspond to the DCB values ​​of B1I_B3I and B1C_B3I, respectively. The DCB values ​​for B1I_B2a and B1C_B2a are respectively provided. The DCB values ​​for B1I_B3I, B1C_B3I, and B1C_B2a can be directly obtained from Table 3. The DCB value for B1I_B2a needs to be converted from other frequency points. The conversion relationship is expressed as follows:

[0055] DCB B1I_B2a =DCB B1C_B2a -DCB B1C_B3I +DCB B1I_B3I (10)

[0056] DCB B1I_B2a DCB represents the code deviation between the frequencies of Beidou B1I and B2a. B1C_B2a DCB represents the code deviation between the frequencies of Beidou B1C and B2a. B1C_B3I DCB represents the code deviation between the BeiDou B1C and B3I frequencies. B1I_B3I This indicates the code deviation between the BeiDou B1I and B3I frequencies.

[0057] S4. Calculate satellite clock error correction, tropospheric error correction (Saastamoinen model), Earth rotation correction, and relativistic effect correction based on the empirical error processing model;

[0058] S5. Using various error correction values ​​and the corrected three-frequency combined observation values, construct the three-frequency deionization ionospheric combined pseudorange observation equation, and then use least squares parameter estimation to obtain the user's final XYZ positioning result in the spatial rectangular coordinate system.

[0059] To verify the correctness of the BDS-3 three-frequency de-ionization combination and the three-frequency DCB correction formula, the experimental positioning results were compared with the actual coordinates. The pseudorange single-point positioning plane and elevation direction positioning error distributions of the B1I / B2a / B3I and B1C / B2a / B3I three-frequency de-ionization combinations in this invention are as follows: Figure 2 , Figure 3As shown. It should be noted that if the BDS-3 three-frequency ionospheric desiccation combination is not corrected by DCB, the pseudorange single-point positioning result deviates too much from the true value (more than 10 meters) or the least squares iteration cannot calculate the result. In this invention, the true coordinates of the experimental data are obtained from the station coordinate result file provided by IGS. After verification, it was found that the method of this invention can effectively improve the accuracy of BDS-3 three-frequency pseudorange single-point positioning.

Claims

1. A BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction, characterized in that, Includes the following steps: S1. Obtain the raw observation data file, satellite broadcast ephemeris file, and differential code bias correction file; S2. Perform smoothing filtering and gross error removal on the raw observation data to obtain the processed satellite observation values; S3. Combine the observations from BeiDou B1I / B2a / B3I and B1C / B2a / B3I satellites with three frequencies to eliminate ionospheric interference, and correct the combined observations with three-frequency differential code bias to obtain the corrected three-frequency combined observations. S4. Calculate satellite clock error correction, tropospheric error correction, Earth rotation correction, and relativistic effect correction based on the empirical error processing model; S5. Construct the three-frequency deionization pseudorange observation equation using the error correction value and the corrected three-frequency combined observation value, and then use the least squares parameter estimation to obtain the user's final XYZ positioning result in the spatial rectangular coordinate system. The corrected three-frequency combined observation values ​​are used to construct the three-frequency de-ionization combined pseudorange observation equation as follows: in These are observations from the BeiDou three-frequency deionization combination. Indicates the distance from the satellite to the receiver. Indicates the speed of light propagation. Indicates receiver clock bias. Indicates satellite clock bias, Indicates tropospheric error. This indicates the differential code deviation correction for the three-frequency combination; in This indicates code deviation correction at frequency B1. This indicates code deviation correction at frequency B2. These represent the combination coefficients of pseudorange observations at frequency points B1 and B2, respectively. These correspond to the DCB values ​​of B1I_B3I and B1C_B3I, respectively. These correspond to the DCB values ​​of B1I_B2a and B1C_B2a, respectively. The DCB value of B1I_B2a needs to be converted from other frequency points. This indicates the code deviation between the frequencies of Beidou B1I and B2a. This indicates the code deviation between the frequencies of Beidou B1C and B2a. This indicates the code deviation between the BeiDou B1C and B3I frequencies. This indicates the code deviation between the BeiDou B1I and B3I frequencies.

2. The BDS-3 three-frequency pseudorange single-point positioning method based on DCB correction according to claim 1, characterized in that, satisfy: in This represents the combination coefficient of pseudorange observations at frequency point B3. These are the coefficients of the pseudorange observation frequencies at the three frequency points B1, B2, and B3, respectively.

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