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Open AccessArticle

Combined GPS/GLONASS Precise Point Positioning with Fixed GPS Ambiguities

1
School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
2
Sciences Géomatiques, Université Laval, Québec G1V 0A6, Canada
*
Author to whom correspondence should be addressed.
Sensors 2014, 14(9), 17530-17547; https://doi.org/10.3390/s140917530
Received: 10 July 2014 / Revised: 30 August 2014 / Accepted: 9 September 2014 / Published: 18 September 2014
(This article belongs to the Section Remote Sensors)
Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF. View Full-Text
Keywords: GPS; GLONASS; precise point positioning; integer ambiguity resolution GPS; GLONASS; precise point positioning; integer ambiguity resolution
MDPI and ACS Style

Pan, L.; Cai, C.; Santerre, R.; Zhu, J. Combined GPS/GLONASS Precise Point Positioning with Fixed GPS Ambiguities. Sensors 2014, 14, 17530-17547.

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