Performance of global navigation satellite systems (GNSS) in absence of GPS observations

Abstract

Over the last decades, a wide range of applications that require positioning relied on the global positioning system (GPS) established by the US Department of Defence (DOD). However, depending on a single constellation may not be sufficient to guarantee a successful positioning accuracy at any time. Consequently, having several constellations that can be used for positioning offers the opportunity to maintain continuous positioning. This became possible with the global coverage of other constellations such as GLONASS, designed by Russia, Galileo, designed by the European Union, and BeiDou, designed by China. In this research, the accuracy of using each of these constellations individually is assessed and compared to the accuracy obtained from GPS to validate the possibility of using these constellations in positioning in the absence of GPS. For this purpose, Global Navigation Satellite Systems (GNSS) data were collected from five stations in Cairo, Egypt using GNSS receivers. The results indicate that using GLONASS, Galileo, and BeiDou can overcome the problematic periods during GPS signal outages. In addition, the different duration lengths of static positioning results indicate that using GLONASS-only or BeiDou-only for positioning provides less accuracy than GPS-only in both horizontal and vertical directions. Furthermore, as a standalone positioning constellation, Galileo can be used now to replace GPS. Moreover, Galileo, GLONASS, and BeiDou improve the positioning accuracy by 0.007 m over the GPS-only model. Therefore, the solution can reach reliable precision levels that can be exploited for the high-accuracy-demanding postprocessing applications in Egypt and the surrounding area.