Test and Analysis of GPS／BDS／GLONASS Combined Pseudo range Point Positioning Performance

This paper takes practical problems that mountains and buildings are a shelter from GNSS sateliites in the alpine gorge area and city building area as the starting point,and researches pseudorange point positioning model of GPS／BDS,GPS／GLONASS,and GPS／BDS／GLONASS combined systems improve the accuracy and usability in threedimensional navigation comparing with GPS or BDS in different occlusion environment that is simulated by selecting different azimuth. The results show that the combined system compared with the single system, increase the number of visible satellites, reduced the PDOP value.When the poor observation conditions, the combined systems can greatly improve the positioning accuracy and the usability in threedimensional navigation.