Satellite navigation real-time precise single-point positioning method based on broadcast ephemerisTechnical Field
The invention relates to the technical field of satellite navigation, in particular to a satellite navigation real-time precise single-point positioning method based on broadcast ephemeris.
Background
The precise single-point positioning technology is a GNSS positioning measurement technology developed in the last twenty years, and can realize high-precision absolute positioning under a dynamic global reference frame by only a single GNSS receiver, and has the advantages of low cost, flexibility, no restriction of working distance and the like, and gradually becomes a research hotspot in the field of satellite navigation positioning. The implementation of precise single point positioning has been dependent on the high precision satellite orbit and clock error information provided in the precise ephemeris issued by the institutions. Compared with the precise ephemeris, the broadcast ephemeris has higher timeliness and stability, but is not adopted in precise single-point positioning because of poor precision of provided satellite orbit and clock error; with the continued development of GNSS, the GPS/Galileo/BDS-3 system can provide broadcast ephemeris with higher accuracy; therefore, the research on the real-time precise single-point positioning technology based on the broadcast ephemeris has extremely strong practical significance for improving the precision and timeliness of satellite navigation positioning.
Disclosure of Invention
Aiming at the defects of the existing algorithm, the invention fully utilizes the pseudo-range observation values and carrier phase observation values of GPS, galileo and BDS-3 satellites, realizes high-precision satellite navigation positioning based on broadcast ephemeris broadcast by satellites, and improves the precision of satellite navigation positioning; and the position parameters of the subscriber station are resolved in real time by using the broadcast ephemeris, so that the real-time satellite navigation positioning is realized, and the timeliness of the satellite navigation positioning is improved.
The technical scheme adopted by the invention is as follows: a satellite navigation real-time precise single-point positioning method based on broadcast ephemeris comprises the following steps:
s1, extracting pseudo-range observation values, carrier phase observation values and broadcast ephemeris of a navigation system GPS, galileo and BDS-3 satellites from an original observation file of a GNSS receiver, and preprocessing GNSS data;
s2, calculating the broadcasting orbit and broadcasting clock difference of the satellite at each moment through the interpolation of the broadcasting ephemeris Lagrange polynomials;
s3, calculating broadcast ephemeris space signal ranging errors (SISRE) of the GNSS satellites according to the broadcast orbit and broadcast clock difference data through the method (1):
wherein R, A and C represent radial, tracking, and normal satellite orbit errors, respectively, for broadcast ephemeris; Δcdt represents the satellite clock bias of the broadcast ephemeris; w (w)R And wA,C A contribution factor representing SISRE; RMS represents the Root Mean Square (Root Mean Square) of the error;
s4, establishing a broadcast ephemeris-based multisystem precise single point positioning model with SISRE compensation, wherein SISRE is used as a random walk process parameter for estimation:
wherein p and l represent pseudorange and carrier phase observations, respectively; g represents GPS, Q represents Galileo and BDS-3; x represents a three-dimensional coordinate, and u is a corresponding direction vector;
representing receiver clock skew; />
Representing the system time offset between Galileo or BDS-3 and GPS; z is Z
w Represents zenith direction tropospheric delay, M
w Is a corresponding projection function; />
Representing ionospheric delay, gamma
i Is an ionospheric amplification factor; />
Representing carrier phase ambiguity; s represents SISRE compensation parameters; epsilon and xi represent pseudorange and carrier phase observation noise, respectively;
s5, coordinate parameter calculation is carried out through a multisystem precise single-point positioning model based on broadcast ephemeris, wherein SISRE parameters adopt different process noises to carry out random walk process estimation, sensitivity analysis is carried out on a series of obtained coordinate parameter solutions, and an optimal coordinate parameter solution is determined, so that the optimal random walk process noise of SISRE parameters of each GNSS system is determined;
s6, taking the SISRE value obtained in the S3 as an initial value of SISRE parameter estimation, taking the optimal process noise obtained in the S6 as random walk process noise of SISRE, and resolving a SISRE-compensated multisystem precise single-point positioning model based on broadcast ephemeris through Kalman filtering to obtain a real-time high-precision coordinate parameter solution of each epoch;
the beneficial effects of the invention are as follows:
1. the broadcast ephemeris has higher timeliness and stability compared with the precise ephemeris, and the real-time precise single-point positioning mode of the broadcast ephemeris can provide the position information required by the user in a shorter time.
2. The broadcast ephemeris broadcast by Galileo and BDS-3 at present has higher precision; according to the precision single-point positioning method, the positioning precision is improved from the meter level of pseudo-range single-point positioning to the decimeter level on the premise of ensuring high timeliness.
Drawings
FIG. 1 is a flow chart of a precise GPS/Galileo/BDS-3 single point positioning method based on broadcast ephemeris of the present invention;
FIG. 2 is a random walk process noise plot of GPS, galileo and BDS-3 system optimal SISRE parameters;
FIG. 3 is a diagram of the result of station static coordinate resolution;
fig. 4 is a diagram of the result of the station dynamic coordinate calculation.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples, which are simplified schematic illustrations showing only the basic structure of the invention and thus showing only those constructions that are relevant to the invention.
In the embodiment, the MGEX continuous operation observation station NKGG is selected, and can simultaneously receive the GPS, galileo and BDS-3 double-frequency observation data, wherein the data observation time is 24-hour continuous observation data of 2021, 11 months and 1 days.
As shown in fig. 1, a satellite navigation real-time precise single-point positioning method based on broadcast ephemeris includes the following steps:
s1, extracting pseudo-range observation values, carrier phase observation values and broadcast ephemeris of GPS, galileo and BDS-3 satellites from an original observation file of a GNSS receiver; preprocessing GNSS data, performing cycle slip detection by combining MW combination and GF combination, and eliminating observation data with cycle slip; correcting errors such as satellite and receiver antenna phase centers, earth rotation, relativistic effects, antenna phase winding and the like in the observed values through an error model;
s2, calculating the broadcasting orbit and broadcasting clock difference of the satellite at each moment through the interpolation of the broadcasting ephemeris Lagrange polynomials;
s3, calculating broadcast ephemeris space signal ranging errors (SISRE) of the GNSS satellites according to the broadcast orbit and broadcast clock difference data through the method (1):
wherein R, A and C represent radial, tracking, and normal satellite orbit errors, respectively, for broadcast ephemeris; Δcdt represents the satellite clock bias of the broadcast ephemeris; w (w)R And wA,C A contribution factor representing SISRE; RMS represents the Root Mean Square (Root Mean Square) of the error;
s4, establishing a broadcast ephemeris-based multisystem precise single point positioning model with SISRE compensation, wherein SISRE is used as a random walk process parameter for estimation:
wherein p and l represent pseudorange and carrier phase observations, respectively; g represents GPS, Q represents Galileo and BDS-3; x represents a three-dimensional coordinate, and u is a corresponding direction vector;
representing receiver clock skew; />
Representing the system time offset between Galileo or BDS-3 and GPS; z is Z
w Represents zenith direction tropospheric delay, M
w Is a corresponding projection function; />
Representing ionospheric delay, gamma
i Is an ionospheric amplification factor; />
Representing carrier phase ambiguity; s represents SISRE compensation parameters; epsilon and xi represent pseudorange and carrier phase observation noise, respectively;
s5, coordinate parameter calculation is carried out through a multisystem precise single-point positioning model based on broadcast ephemeris, SISRE parameters adopt different process noises to carry out random walk process estimation, and a series of obtained coordinate parameter solutions are carried out; performing sensitivity analysis to determine an optimal coordinate parameter solution so as to determine optimal process noise of SISRE of each GNSS system; 1mm is adopted as an interval of SISRE sensitivity analysis, and random walk process noise of the optimal SISRE parameters of each GNSS system is analyzed through a test; FIG. 2 shows the results of SISRE sensitivity analysis for each of the GPS, galileo and BDS-3 systems; the result of the graph is used for giving random walk process noise of the optimal SISRE parameters of each GNSS system, the SISRE optimal process noise of the GPS and BDS-3 systems is about 8mm, and the SISRE optimal process noise of the Galileo is about 4 mm.
S6, taking the SISRE value obtained in the step S3 as an initial value of SISRE parameter estimation, taking the optimal process noise obtained in the step S5 as random walk process noise of SISRE, and resolving a multi-system precise single-point positioning model based on broadcast ephemeris compensated by SISRE through Kalman filtering to obtain a real-time high-precision coordinate parameter solution of each epoch; FIG. 3 shows a solution result of static coordinates of a measuring station, and the positioning accuracy of the GPS/Galileo/BDS-3 real-time precise single-point positioning method based on broadcast ephemeris can be obtained, which is obviously superior to that of the traditional SPP method; FIG. 4 shows the dynamic coordinate calculation result, and the positioning accuracy of the GPS/Galileo/BDS-3 real-time precise single-point positioning method based on broadcast ephemeris is better than that of SPP.
With the above-described preferred embodiments according to the present invention as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.