Precise Point Positioning Using Combined GPS and GLONASS Observations

Precise Point Positioning (PPP) is currently based on the processing of only GPS observations. Its positioning accuracy, availability and reliability are very dependent on the number of visible satellites, which is often insufficient in the environments such as urban canyons, mountain and open-pit mines areas. Even in the open area where sufficient GPS satellites are available, the accuracy and reliability could still be affected by poor satellite geometry. One possible way to increase the satellite signal availability and positioning reliability is to integrate GPS and GLONASS observations. Since the International GLONASS Experiment (IGEX-98) and the follow-on GLONASS Service Pilot Project (IGLOS), the GLONASS precise orbit and clock data have become available. A combined GPS and GLONASS PPP could therefore be implemented using GPS and GLONASS precise orbits and clock data. In this research, the positioning model of PPP using both GPS and GLONASS observations is described. The performance of the combined GPS and GLONASS PPP is assessed using the IGS tracking network observation data and the currently available precise GLONASS orbit and clock data. The positioning accuracy and convergence time are compared between GPS-only and combined GPS/GLONASS processing. The results have indicated an improvement on the position convergence time but correlates to the satellite geometry improvement. The results also indicate an improvement on the positioning accuracy by integrating GLONASS observations.