中文摘要：

本文以高山峡谷地区以及城市建筑群区域GNSS卫星受山体及建筑物遮挡的实际问题为出发点,通过选取不同的卫星方位角模拟不同遮挡环境,研究GPS/BDS、GPS/GLONAS和GPS/BDS/GLONASS组合系统伪距单点定位模型对于单GPS、单BDS系统在不同遮挡环境下的定位精度和三维导航可用性等方面的改善情况。结果表明,组合系统相对于单系统,增加了可见卫星数,降低了PDOP值,当观测条件不佳时,可以很好地改善定位精度和提高三维导航可用性。

英文摘要：

This paper takes practical problems that mountains and buildings are a shelter from GNSS satellites 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.