Research on the Fitting Algorithm of GLONASS Broadcast Ephemeris Parameters

Abstract

Abstract. The accumulated error of GLONASS broadcast ephemeris is nearly 1 meters within 15 minutes due to simplified perturbation force model. Aiming at this problem, a new method of GLONASS broadcast ephemeris fitting algorithm is introduced. In this method, a nonlinear measurement model is built based on the GLONASS broadcast ephemeris user algorithm and linearized. And the partial derivative of Jacobin matrix is computed by difference quotient approximation. Then the GLONASS broadcast ephemeris parameters are estimated by using least square method. The simulation results show that the average user range error (URE) caused by fitting broadcast ephemeris is improved about two orders compared with the traditional broadcast ephemeris and achieves millimeter level. Finally, a verification system was built by the Japanese RTKLIB tools, the availability of the fitting broadcast ephemeris is validated from the positioning angle.

Developing and validating an optimized 19-parameter broadcast ephemeris model for LEO satellites

“…Most parameter sets seem to show only a slight influence of eccentricity on the RMS of the fit URE. However, for Set 1 and Set 5, the RMS error increases with greater eccentricity due to its direct relationship with the orbit radius computation formula [16] . When considering the parameters ( 3 us C , 3 uc C ) from Set 5 and their impact on the radial direction, it appears that they may not be potent enough to offset the potential decrease in fitting accuracy resulting from increased eccentricity.…”

“…This suggests that parameter sets lacking significant correction terms that affect the radial direction are more vulnerable to changes in eccentricity. Given the strong correlation between ), the latter pair could compensate for the effects of eccentricity variation on fitting accuracy [16] . Consequently, Set 4 maintains stability in the face of changes in eccentricity when In line with the rule that fit errors should not exceed 10 cm [14] , Sets 6-8, 10, 13, and 14 all comply with this rule.…”

“…This is particularly apparent when the parameters ( utilized. According to[16], there's a pronounced correlation between the parameters representing the radial direction and those representing the along-track direction. The corrections for orbit elements r and u , which correspond to the radial and along-track directions, are governed by the coefficients (…”