Research On Multi-GNSS Precise Point Positioning Theory And Its Application

The rapid development of multi navigation satellite systems and the etstablishment of multi-GNSS experiment have prompted the multi-GNSS precise positioning as an inevitable trend in the development of satellite positioning technology.The systematic research on the basic theory,key technology and its application of multi-GNSS precise point positioning(PPP)are conducted in this thesis.The main research and conclusions are listed as follows:(1)The basic theory of multi-GNSS PPP related to space-time reference framework,frame transformation,GNSS observables and its combinations are studied.Meanwhile,the thesis presents the detailed analysis on error sources of multi-GNSS PPP and the approaches for error elimination.(2)The precise point positioning model of single-mode as well as multi-GNSS,parameter estimation of Kalman filter and the methods of quality control for GNSS observables are studied systematically.(3)The thesis covers the introduction of multi-GNSS experiment(MGEX)and the evaluation on the consistency of multi-GNSS precise ephemeris and precise clock products provided by three analysis centers(ACs),including GFZ,CODE and Wuhan University.Results show that the precise orbit and precise clock offset of GPS,Galileo and BDS MEO satellites among those three ACs have a good consistency,and the consistency of precise clock offset corrections between GBM and WUM is relatively high.(4)Based on gnss observables,precise orbit and precise clock offset of multi-GNSS,the performance of single-GPS system,GPS/BDS combined PPP in static and post-processing kinematic mode are evaluated and illustrated.In addition,the research on precipitable water vapor retrieval based on undifferen,ced PPP method is also conducted with GNSS observables of HKSC station in Hong Kong and sounding data of co-location radiosonde station 45004.Results indicated that,compared to the results of GPS PPP,the convergence speed of GPS/BDS combined PPP in static mode has improved,but positioning accuracy of static solution with less improvement.In addition,the number of BDS satellites and its orbital quality have an effect on the positioning solution of GPS/BDS combined PPP.For the lack of BDS MEO satellites that obtains a high quality in orbit determination with better geometry strength,the convergence time of BDS PPP in static mode takes 30 min and 60?70 min to obtain 1 dm positioning accuracy in east and up directions,respectively.The positioning precision in static mode after convergence is also lower than the GPS PPP results,when there are few GPS satellites in the field of view,the convergence time of GPS/BDS combined in post-processing kinematic reduces by 26.4%,18.6%and 30.9%in east,west and up directions with respect to the GPS PPP,respectively.The positioning accuracy improve by 25.5%,21.1%and 29.8%in east,west and up directions,respectively,which indicates the addition of BDS observables can improve the convergence speed and positioning accuracy in kinematic PPP mode.Furthermore,precipitable water vapor of atmosphere in station HKSC with the RMS of 1.4 mm can be achieved by means of undifferenced PPP technology combined with measured meteorological data,compared to the PWV calculated by GPS PPP,PWVdetermined by GPS/GLONASS combined PPP have a slight improvement in precision,while,the overall difference of PWV determined by single-system and multi-GNSS PPP is not significant.