Analysis of The GEO multipath impact on Ionosphere-Free Combination Positioning in BDS system

The satellites constellation of BeiDou regional navigation satellite system (BDS) is different from GPS, which consists of Geostationary Orbit (GEO), Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO). Due to the different constellation of navigation system, there should be some special characteristics of BDS to be analyzed thoroughly. For example, when used Ionosphere-Free Combination Positioning algorithm (IF) in BDS, the positioning accuracy performs worse than Single frequency positioning. This paper studies the genuine causes of this phenomenon initially. From the analysis, GEO multipath error should be the main reason which caused this phenomenon. GEO multipath error changes slowly, even calls “standing multipath error”. This paper analyzes this phenomenon and characteristics of GEO multipath error, then proposes an amended algorithm to estimate GEO multipath error. Finally used computed multipath error to correct Ionosphere-Free Combination Positioning. The simulation results show a significant promotion in positioning accuracy.