在依靠RTK技术提供实时精密定位服务的系统中，需要依靠精密后处理方法事先求得各个基准站的精确地心坐标。为方便用户使用，基准站坐标多采用国家2000大地坐标系(CGCS2000)等坐标。而RTK实时定位过程中需要采用IGS所提供的精密轨道或者是卫星广播星历，其基准分别为ITRF或WGS84，导致基准站坐标与卫星轨道的基准不一致，会对流动站的定位精度产生一定的影响。本文在分析差分定位的原理的基础上，利用解析方法，推导了卫星轨道、基准站坐标与流动站定位精度三者之间的关系，进一步分析了流动站定位精度与基准站间距离的关系，为网络RTK技术的推广使用提供了有益的探讨。%In order to provide real-time precision positioning service, the accurate geocentric coordinate of each base station is needed to be calculated out by sophisticated post-processing method beforehand. For the convenience of users, the datum always uses national Geodetic System 2000 (CGCS2000) coordinates system, etc. However, the datum of the precise orbit or satellite broadcast ephemeris(required in real-time positioning and provided by IGS) is ITRF or WGS84. And then the inconsistent of datum will cause effects on the positioning accuracy of moving stations. Based on the analysis of the principle of differential positioning, this paper deduces the relationship between satellite orbits, coordinate of base station and positioning accuracy of moving station by using analytical methods. The relationship between the positioning accuracy of moving station and its distance to base station is further analyzed to provide a useful discussion for promoting the use of network RTK technology.
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