To determine the position of user, Global Positioning System (GPS) uses the signals transmitted from the satellites. The positioning accuracy of global Positioning System depends on a variety of influence factors. The GPS system performance is assessed with reference to carrier-to-noise density ratio (C/N0), pseudorange, satellite orbit and satellite clock errors. User navigation error depends on DOP factor, user range and equipment errors. User range errors are also called as Signal in Space Ranging Errors (SISRE). Ephemeris error decided by the broadcast ephemeris data uploaded by the control station. User range error (URE) is widely used to measure the effects of satellite orbit error and clock error on user positioning. Position accuracy of each satellite, geometry of the satellites and measurement of pseudorange are also important factors for determining the accurate position of user.
Arasavali, N., Gottapu, S., & Ashok Kumar, N. (2019). Gps signal in space error analysis and positioning performance using iwo for southern region of indian subcontinent. International Journal of Recent Technology and Engineering, 8(1), 2672–2676.