Abstract
The characteristic of the satellite repeat shift time can reflect the status of the satellite operation, and is also one of the key factors of the sidereal filtering multipath correction. Although some methods have been developed to calculate the repeat shift time, few efforts have been made to analyze and compare the performance of this feature for the GPS (Global Positioning System), BDS (BeiDou System), and Galileo in depth. Hence, three methods used for calculating the repeat shift time are presented, and used to compare and analyze the three global systems in depth, named the broadcast ephemeris method (BEM), correlation coefficient method (CCM), and aspect repeat time method (ARTM). The experiment results show that the repeat shift time of each satellite is different. Also, the difference between the maximum and minimum varies from different systems. The maximum difference is about 25 s for the BDS IGSO (Inclined Geosynchronous Orbit) and the minimum is merely 10 s for the GPS system. Furthermore, for the same satellite, the shift time calculated by the three methods is almost identical, and the maximum difference is only about 7 s between the CCM and the ARTM method for the BDS MEO (Medium Earth Orbit) satellite. Although the repeat shift time is different daily for the same satellite and the same method, the changes are very small. Moreover, in terms of the STD (Standard Deviation) of the BS (between satellites) and MS (mean shift for the same satellite), the GPS system is the best, the performance of the BDS system is medium, and the Galileo performs slightly worse than the GPS and BDS.
Highlights
For global navigation systems, the satellite has the characteristic of a repeat period, which means that the satellite will appear in the same position with a period for the ground static user
Choi et al [7] adopted broadcast ephemeris values and Kepler’s third law to estimate the satellite repeat period of the GPS satellite, and the results showed that the repeat periods of the satellites are not precisely a sidereal day and are distinct from each satellite
Wang et al [22] compared the three methods by using the GPS satellite, and the results showed that the differences between the repeat shift time from the three methods are less than 1.2 s on average, the broadcast ephemeris method has the lowest computation, and the aspect repeat time method is optimal for real-time applications
Summary
The satellite has the characteristic of a repeat period, which means that the satellite will appear in the same position with a period for the ground static user. Can this feature of the satellite be used to predict the satellite position, but it can mitigate multipath errors and observation noise effectively. Authors [2,3,4,5] used the satellite repeat shift time to reduce the noise for long baselines or isolate signals from multipath error. Seeber et al [6] pointed out that the satellite repeat shift time of the GPS satellite is Algorithms 2019, 12, 233; doi:10.3390/a12110233 www.mdpi.com/journal/algorithms
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