Accuracy of GNSS Positioning Using GIPSY-X PPP with the Combinations of GPS, GLONASS, and GALILEO

Abstract The positioning accuracy of global navigation satellite systems (GNSS) is important for conducting effective fieldwork, designing geodetic networks, and achieving desired deformation rates. Over the years, the positioning accuracy of the global positioning system (GPS) has been extensively studied, and mathematical models for the north, east, and up coordinate components have been developed. Today researchers have turned their attention to studying the accuracy of multiGNSS (MGEX) positioning. NASA’s GNSS software GIPSY-X provides a framework capable of producing positioning information for GPS and European satellite navigation system (GALILEO) data. A positioning-accuracy model is also available for GIPSY-X solutions; however, it only uses GPS data, and is outdated today. In order to determine the accuracy of GIPSY-X GNSS positioning, we use the processing products of NASA’s Jet Propulsion Laboratory (JPL) in which the data are also available for Global Navigation Satellite System of Russia (GLONASS), and this multiGNSS product set was available only for a short period of time in 2019. We assess the accuracy performance of the GPS-only solution (G) against each of the various combinations of these three constellations (GRE, GR, GE) for continuous data. Using the publicly available data from the NASA 2019 experiment, the accuracy of positioning from short observation sessions (i.e., considered to be 4- and 8-h GNSS campaigns) is also assessed against 24-h continuous measurements. The PPP module of GIPSY-X is employed to produce the position solutions. Furthermore, we derive accuracy prediction models based on the observation session duration for each of the various GNSS constellation combinations. As expected, the best accuracy is obtained by the combination of all three constellations (GRE solution), and the GRE solution, on average, is superior to the GPS-only solution by about 9%, 16%, and 14% for north, east, and up coordinates. The impact is slightly greater on the GNSS campaign solutions and hence is promising for the studies conducting episodic GNSS measurements to monitor natural hazards and engineering structures.