Abstract
A joint-processing model for multi-GNSS (GPS, GLONASS, BDS and GALILEO) precise point positioning (PPP) is proposed, in which raw code and phase observations are used. In the proposed model, inter-system biases (ISBs) and GLONASS code inter-frequency biases (IFBs) are carefully considered, among which GLONASS code IFBs are modeled as a linear function of frequency numbers. To get the full rank function model, the unknowns are re-parameterized and the estimable slant ionospheric delays and ISBs/IFBs are derived and estimated simultaneously. One month of data in April, 2015 from 32 stations of the International GNSS Service (IGS) Multi-GNSS Experiment (MGEX) tracking network have been used to validate the proposed model. Preliminary results show that RMS values of the positioning errors (with respect to external double-difference solutions) for static/kinematic solutions (four systems) are 6.2 mm/2.1 cm (north), 6.0 mm/2.2 cm (east) and 9.3 mm/4.9 cm (up). One-day stabilities of the estimated ISBs described by STD values are 0.36 and 0.38 ns, for GLONASS and BDS, respectively. Significant ISB jumps are identified between adjacent days for all stations, which are caused by the different satellite clock datums in different days and for different systems. Unlike ISBs, the estimated GLONASS code IFBs are quite stable for all stations, with an average STD of 0.04 ns over a month. Single-difference experiment of short baseline shows that PPP ionospheric delays are more precise than traditional leveling ionospheric delays.
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Acknowledgments
The authors would like to acknowledge the IGS Multi-GNSS Experiment (MGEX), Center for Orbit Determination in Europe (CODE), GNSS Center in Wuhan University and Chinese International GNSS Monitoring and Assessment System (iGMAS) for providing access to Multi-GNSS data, precise orbit/clock products and differential code bias (DCB) products. We also acknowledge the funding supports by Collaborative Precision Positioning Project funded by Ministry of Science and Technology of China (No. 2016YFB0501900), China Natural Science Funds (No. 41231064, 41674022, 41574033, 41321063) and National 973 (No. 2012CB825604).
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Liu, T., Yuan, Y., Zhang, B. et al. Multi-GNSS precise point positioning (MGPPP) using raw observations. J Geod 91, 253–268 (2017). https://doi.org/10.1007/s00190-016-0960-3
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DOI: https://doi.org/10.1007/s00190-016-0960-3