Quasi Real-time BDS Zenith Troposphere Delay Estimation With Precise Point Positioning

BeiDou satellite system(BDS)is now having the ability to provide navigation,positioning and timing services to Asia Pacific Region.Therefore,carring out theoretical and experimental research on real-time BDS Zenith Troposphere Delay(ZTD)estimation using presice point positioning(PPP)is essential for promoting the application of BDS in quasi real-time weather forecast.Based on the basic theory of PPP,the correction measures of error resources and methods parameters estimation are analyzed in detail.During the quasi real-time estimation of BDS ZTD,the corresponding phase center correction should be used and fixing coordinates can improve the stability of BDS ZTD estimation.Due to the uncertain system models and interference of outside environment with PPP method,an improved fading filter combined with the moderate robust filtering based on the posterior residual is proposed,in which the forgetting factor is extended to the forgetting matrix.The experimental results show that new algorithm can obviously accelerate the convergence speed of positioning,which is a good example for estimating BDS ZTD.The algorithm of quasi real-time estimation of clock difference is realized with undifferenced network method.Observation data come from 45 Mutil-GNSS Experiment(MGEX)stations.The experimental results show that the accuracy of three kinds of BDS satellites clock is between 0.04?0.08ns,which is a little worse than Global Positioning System(GPS).At last,quasi real time estimation of BDS ZTD is conducted and the MGEX stations in Asia region which have not been used in clock estimation are chosen.The experimental results show that the RMS of quasi real-time estimation of BDS ZTD is better than 15mm and STD is better than 14mm,meeting the precision of estimating BDS ZTD.