GNSS Orbits、Clocks Combination And Analysis On The Precision

The development of satellite navigation systems has been booming since April 27,1995,when the US Global Positioning System(GPS)was fully operated.In order to further promote the compatibility and interoperability of multi-GNSS,on the IGG-6 preparatory meeting,June 2011,the International Cooperative Research Centre Management Office Chinese satellite cooperation system first proposed an international GNSS monitoring and evaluation system(International GNSS Monitoring and Assessment System,iGMAS).The main task of iGMAS is to establish the full arc of GNSS satellites,multiple real-time coverage of global tracking network,as well as information service platform with data collection,storage,analysis,management,publishing and other functions,monitor and evaluate the global satellite navigation system health and key performance indicators,generate high precision ephemeris,satellite clock error,This paper mainly focuses on the method of orbit and clock solutions combination,and the analysis of the iGMAS final orbit and clock products.The main content of this thesis is as follows:1.Orbits products combination algorithm is proposed.In order to verify the correctness of the algorithm,the GPS week 1774-1777 of the IGS analysis centers GPS final orbit was combined using the algorithm.Taking the IGS final combined orbit as the reference,the paper gets the difference.It can be seen from the result that the three-dimensional difference between the combined orbit of this paper and the IGS orbit is within 5mm.2.Clocks products combination algorithm is proposed.In order to verify the correctness of the algorithm,the GPS week 1774-1777 of the IGS analysis centers GPS final clock was combined using the algorithm.Taking the IGS final combined clock as the reference,the paper gets the difference.It can be seen from the result that the difference between the combined clock of this paper and the IGS orbit is within 40ps.3.Compared with the IGS final orbit,the result shows that the accuracy of combined iGMAS GPS orbit is the best,and that the combined orbit accuracy is 1 cm,the analysis centers orbit accuracy is 3 cm;for the GLONASS orbit,the accuracy of combined orbit is 1.7cm,the accuracy of all the analysis centers is better than 8 cm;for the Galileo satellite orbit,in addition to individual analysis center,one-dimensional accuracy is more than 15 cm,the majority is better than 10 cm,and the one-dimensional accuracy of combined Galileo satellite orbit is range from 4-12 cm.;for the BDS GEO satellite orbit,the accuracies of all the analysis centers within 4 m,and the accuracies of combined BDS GEO orbit is within 1.4m;the accuracy of IGSO/MEO satellite orbit is better than those of the GEO satellites,the majority of the analysis centers are better than 15 cm,and the final combined orbit of the one-dimensional accuracy is still the best,better than 10 cm.4.For BDS and Galileo satellite orbits,SLR measurements are collected and used for orbit validation,the systematic errors in SLR residuals for GEO and Galileo orbits.are found,an analysis about stability of reference system implied in the combined orbits is analyzed and a rigorous combination method should be adopted.Finally,a priori solar radiation pressure(SRP)model is proposed for precise orbit determination of BDS GEO satellites,with the help of the a priori mode,the satellite orbit angle dependence systematic error in SLR residuals is reduced by about 40%.5.Compared with the IGS final clock,the result shows that the accuracy of combined iGMAS GPS clcok is range from 0.04 ns-0.06 ns,the analysis centers clock accuracy is range from 0.1 ns-0.4 ns;for the GLONASS clock,the minority of analysis centers accuracy is within 0.1 ns,the accuracy of combined clock is within 0.1 ns;for the Galileo satellite orbit,in addition to individual analysis center,,the majority is within 1 ns,and the accuracy of combined Galileo clock is range from 0.1 ns-0.3 ns;for the BDS GEO satellite clock,the accuracies of all the analysis centers is range from 0.4 ns-0.9 ns,and the accuracies of combined BDS GEO clock is range from 0.3 ns-0.7 ns;the accuracy of IGSO/MEO satellite clock is better than those of the GEO satellites,the accuracies of all the analysis centers is range from 0.2 ns-0.8 ns,and the accuracies of combined BDS IGSO/MEO clock is range from 0.1 ns-0.2 ns.6.In order to evaluate the consistency of the iGMAS final orbit products and the final clock products,precise point positioning experiment was carried out.Compared to the results of PPP using IGS final orbits and clocks,the RMS of GPS static PPP using iGMAS GPS final orbits and clocks is 1.91,1.57 and 4.12 mm in E,N,U respectively;the RMS of GLONASS static PPP using iGMAS GLONASS final orbits and clocks is 14.03,8.41 and 19.03 mm in E,N,U respectively;the RMS of Galileo + GPS static PPP using iGMAS Galileo + GPS final orbits and clocks is 15.33,9.18 and 19.40 mm in E,N,U respectively;the RMS of BDS + GPS static PPP using iGMAS BDS + GPS final orbits and clocks is 15.59,4.79 and 10.58 mm in E,N,U respectively.