Undifferenced ionospheric-free ambiguity resolution using GLONASS data from inhomogeneous stations
- 254 Downloads
GLONASS frequency division multiple access signals render ambiguity resolution (AR) rather difficult because: (1) Different wavelengths are used by different satellites, and (2) pseudorange inter-frequency biases (IFBs) cannot be precisely modeled by means of a simple function. In this study, an AR approach based on the ionospheric-free combination with a wavelength of about 5.3 cm is assessed for GLONASS precise point positioning (PPP). This approach simplifies GLONASS AR because pseudorange IFBs do not matter, and PPP-AR can be enabled across inhomogeneous receivers. One month of GLONASS data from 165 European stations were processed for different network size and different durations of observation periods. We find that 89.9% of the fractional parts of ionospheric-free ambiguities agree well within ± 0.15 cycles for a small network (radius = 500 km), while 77.6% for a large network (radius = 2000 km). In case of the 3-hourly GLONASS-only static PPP solutions for the small network, reliable AR can be achieved where the number of fixed GLONASS ambiguities account for 97.6% within all candidate ambiguities. Meanwhile, the RMS of the east, north and up components with respect to daily solutions is improved from 1.0, 0.6, 1.2 cm to 0.4, 0.4, 1.1 cm, respectively. When GPS PPP-AR is carried out simultaneously, the positioning performance can be improved significantly such that the GLONASS ambiguity fixing rate rises from 74.4 to 95.4% in case of hourly solutions. Finally, we introduce ambiguity-fixed GLONASS orbits to re-attempt GLONASS PPP-AR in contrast to the above solutions with ambiguity-float orbits. We find that ambiguity-fixed orbits lead to clearly better agreement among ionospheric-free ambiguity fractional parts in case of the large network, that is 80.5% of fractional parts fall in ± 0.15 cycles in contrast to 74.6% for the ambiguity-float orbits. We conclude that highly efficient GLONASS ionospheric-free PPP-AR is achievable in case of a few hours of data when GPS PPP-AR is also accomplished, and ambiguity-fixed GLONASS orbits will contribute significantly to PPP-AR over wide areas.
KeywordsPrecise point positioning GLONASS Ionospheric-free ambiguity resolution Fractional-cycle bias Inhomogeneous stations
This work is funded by National key R&D plan on strategic international scientific and technological innovation cooperation special project (2016YFE0202300) and National Science Foundation of China (41674033) and State Key Research and Development Programme (2016YFB0501802). We would like to thank IGS and ESA for data and products. The Super Computing Facility at Wuhan University contributes to this study greatly.
- Dai L (2000) Dual-frequency GPSGLONASS real-time ambiguity resolution for medium-range kinematic positioning. In: ION GPS 2000, 19–22 Sept 2000, Salt Lake City, pp 1071–1080Google Scholar
- De Jonge P, Tiberius C (1996) The LAMBDA method for integer ambiguity estimation: implementation aspects. Publications of the Delft Computing Centre, LGR-Series 12Google Scholar
- Hatch R (1982) The synergism of GPS code and carrier measurements. In: Proceedings of the third international symposium on satellite Doppler positioning at Physical Sciences Laboratory of New Mexico State University, vol 2, 8–12 Feb, pp 1213–1231Google Scholar
- Leick A, Beser J, Li J, Mader G (1995) Processing GLONASS carrier phase observations-theory and first experience. In: Proceedings of ION-GPS-95, Institute of Navigation, Palm Springs, California, pp 1041–1047Google Scholar
- Reussner N, Wanninger L (2011) GLONASS inter-frequency biases and their effects on RTK and PPP carrier phase ambiguity resolution. In: Proceedings ION GNSS 2011, Institute of Navigation, Portland, OR, pp 712–716Google Scholar
- Roßbach U (2000) Positioning and navigation using the Russian satellite system GLONASS. Ph.D. Thesis, Universitaet der Bundeswehr MuenchenGoogle Scholar
- Sleewaegen JM, Simsky A, De Wilde W, Boon F, Willems T (2012) Demystifying GLONASS inter-frequency carrier phase biases. Inside GNSS 7(3):57–61Google Scholar
- Wu JT, Wu SC, Hajj GA, Bertiger WI, Lichten SM (1993) Effects of antenna orientation on GPS carrier phase. Manuscr Geodaet 18(2):91–98Google Scholar
- Yamada H, Takasu T, Kubo N, Yasuda A (2010) Evaluation and calibration of receiver inter-channel biases for RTK-GPS/GLONASS. In: Proceedings of the 23rd international technical meeting of The Satellite Division of the Institute of Navigation, Portland, OR, pp 1580–1587Google Scholar