Abstract
Because of the frequency division multiple access (FDMA) technique, Russian global navigation satellite system (GLONASS) observations suffer from pseudo-range inter-channel biases (ICBs), which adversely affect satellite clock offset estimation. In this study, the GLONASS pseudo-range ICB is treated in four different ways: as ignorable parameters (ICB-NONE), polynomial functions of frequency (ICB-FPOL), frequency-specific parameters (ICB-RF), and satellite-specific parameters (ICB-RS). Data from 110 international global navigation satellite system (GNSS) service stations were chosen to obtain the ICBs and were used for satellite clock offset estimation. The ICBs from the different schemes varied from −20 ns to 80 ns. The ICB-RS model yielded the best results, improving the clock offset accuracy from 300 ps to about 100 ps; it could improve the GLONASS precise point positioning (PPP) accuracy and the converging time by approximately 50% and 30%, respectively. Along similar lines, we introduced the GPS-ICB parameters in the process of GPS satellite clock estimation and GPS/GLONASS PPP, as ICBs may exist for GPS because of different chip shape distortions among GPS satellites. This possibility was found to be the case. Further, the GPS-ICB magnitude ranged from −2 ns to 2 ns, and the estimated satellite clock offsets could improve the accuracy of the GPS and combined GPS/GLONASS PPP by 10%; it also accelerated the converging time by more than 15% thanks to the GPS-ICB calibration.
Highlights
Providing high precision satellite orbit and clock products are key to precise point position (PPP) [1,2,3]
The estimated inter-channel biases (ICBs) were introduced into global navigation satellite system (GLONASS) satellite clock offset estimation using the corresponding strategies
We obtained significant results regarding ICB based on seven different manufacturer receivers
Summary
Providing high precision satellite orbit and clock products are key to precise point position (PPP) [1,2,3]. Considering the experiences we obtained in the GLONASS case, we extend this to the GPS case with GPS-ICBs in this study The former works were focused mainly on the characteristics of GPS pseudo-range ICBs [14,18], but barely on their effects on PPP and satellite clock offset estimation, which constitute the main contribution of this work. The details of the ICB characteristics and analyses of the corresponding effects on GLONASS satellite clock offset estimation and PPP are presented next. Considering the chip shapes of GPS signals, the introduction of an ICB parameter into the GPS observation equation is described to analyses of the pseudo-range ICB characteristics and effects on GPS satellite clock offset estimation and PPP.
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