| The launch of the Bei Dou-3 Navigation Satellite System(BDS-3)marks the completion of the Satellite Navigation System(BDS).The research on BDS-3 positioning technology has become one of the hot topics,Precision Point Positioning(PPP)with its high precision,reliability,stability and flexibility has become a widely used precision positioning technique in BDS.BDS all constellation broadcast three frequency signal,has played a great role in promoting the development of PPP technology.However,at present PPP mainly adopts dual-frequency signal,and the accuracy of the ambiguity solution is low.In this paper,the three-frequency precision single point positioning technology of BDS-3 is studied deeply,and a complete PPP system is designed and implemented.The main work and innovations of this thesis are as follows:1.In this thesis,the properties of carrier phase ambiguity in PPP and its solution are studied.Based on the traditional Boot-strapping method,a three-frequency ambiguity solution for BDS-3 PPP is proposed.The proposed method adopts the EWL-EWL-WL-NL solution strategy,by selecting the observation values of the three-frequency combination with longer wavelength,less ionospheric delay and less measurement noise to solve the ambiguity of EWL,WL and NL combinations respectively.It can be seen from the experimental results that compared with the traditional method,the improved method can ensure a higher success rate of ambiguity solution,and for the precision of calculating the narrow lanes combination ambiguity has been increased significantly,the fuzzy degree of fixed estimate can achieve within 3weeks,compared with traditional ambiguity calculating method of combination of narrow lanes,the accuracy of fuzzy estimation of narrow lane combination is improved by about 50%.2.In view of the fact that the precision products of Bei Dou-3 satellite are not perfect at the initial stage of BDS-3 full service,this paper studies the mathematical model of Bei Dou three-frequency PPP and the combined positioning performance of BDS-2+BDS-3,analyzes the systematic deviation between BDS-2 and BDS-3,and makes reasonable parameterization of three commonly used three-frequency PPP models.The PPP models of BDS-2+BDS-3 combination with three frequencies and two ionospheric combinations(IF-1213),three frequencies and two ionospheric combinations(IF-123)and three frequencies and non-difference non-combination(UC-123)are systematically constructed.The positioning performance of the PPP model is compared with that of the traditional PPP model.The static and dynamic PPP positioning performance of BDS-2 and BDS-2+BDS-3 combined with two different constellations is compared.The experimental results show that compared with the dual-frequency IF-12 PPP model,the positioning accuracy and convergence time of the three-frequency PPP model are not significantly improved,and the positioning performance of the three-frequency PPP model is basically the same as that of dual-frequency PPP model.For static and dynamic PPP,the positioning accuracy of BDS-2+BDS-3 in E,N and U directions is better than that of single BDS-2.The average positioning deviations(RMS)of static PPP in E,N and U directions were 0.020 m,0.019 m and 0.039 m,respectively,which increased by 31.0%,32.1% and 27.8%.The average convergence time was 26.7min,18.8min and 32.6min,and the improvement rate was 54.9%,56.6% and 68.3%,respectively.The average positioning deviations(RMS)of dynamic PPP in E,N and U directions are 0.042 m,0.039 m and0.078 m,respectively,which are increased by 25.0%,27.7% and 31.6%.The average convergence time was 36.9min,29.0min and 42.9min,respectively,increasing by 67.9%,72.1% and 78.4%.3.Based on the characteristics of PPP technology,a set of PPP system is designed and implemented,which integrates the functions of signal reception,signal baseband processing,PPP positioning solution,database storage,Web display positioning results and viewing positioning results deviation. |
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