Impact of GLONASS pseudorange inter-channel biases on satellite clock corrections
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GLONASS carrier phase and pseudorange observations suffer from inter-channel biases (ICBs) because of frequency division multiple access (FDMA). Therefore, we analyze the effect of GLONASS pseudorange inter-channel biases on the GLONASS clock corrections. Different Analysis Centers (AC) eliminate the impact of GLONASS pseudorange ICBs in different ways. This leads to significant differences in the satellite and AC-specific offsets in the GLONASS clock corrections. Satellite and AC-specific offset differences are strongly correlated with frequency. Furthermore, the GLONASS pseudorange ICBs also leads to day-boundary jumps in the GLONASS clock corrections for the same analysis center between adjacent days. This in turn will influence the accuracy of the combined GPS/GLONASS precise point positioning (PPP) at the day-boundary. To solve these problems, a GNSS clock correction combination method based on the Kalman filter is proposed. During the combination, the AC-specific offsets and the satellite and AC-specific offsets can be estimated. The test results show the feasibility and effectiveness of the proposed clock combination method. The combined clock corrections can effectively weaken the influence of clock day-boundary jumps on combined GPS/GLONASS kinematic PPP. Furthermore, these combined clock corrections can improve the accuracy of the combined GPS/GLONASS static PPP single-day solutions when compared to the accuracy of each analysis center alone.
KeywordsGLONASS Clock corrections Day-boundary jump Inter-channel bias Clock combination
We thank Simon Banville, at NRCan, and Maorong Ge, at GFZ, for their valuable suggestions on this study. The IGS is acknowledged for providing high-quality combined GPS/GLONASS precise orbit and clock corrections as well as tracking data. This study was supported by the National Natural Science Funds (Grant No. 41374034), the National High Technology Research and Development Program of China (863 Program) (Grant No. 2012AA12A202) and also by China Postdoctoral Science Foundation (Grant No. 2012M511671).
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