Research On Real-time Precise Point Positioning Based On SSR Prediction

With the continuous improvement and development of satellite navigation and positioning technology.Real-Time Precise Point Positioning(RT-PPP)is the preferred way to provide absolute high-precision maritime location services.Continuous State Space Representation(SSR)precision satellite clock correction and orbit data is the key factor to ensure the continuous high precision of RT-PPP.Affected by the delay and lack of SSR data broadcast by maritime satellites,it will cause large correction errors or even interruptions in the satellite’s precise orbit and clock correction,thereby reducing the continuity of highprecision positioning.Therefore,how to effectively maintain the high accuracy of the realtime precision clock correction and orbit in the case of SSR data broadcast delay and interruption needs to be focused on research.Taking the RT-PPP and real-time precision clock correction and orbit based on SSR corrected data format as the research object,this article analyzes the accuracy of real-time precision products,the PPP method taking into account the interruption of SSR data,and the design and implementation of RT-PPP positioning software.Research is carried out to maintain the accuracy of the clock correction and orbit under the delay and interruption of SSR data broadcast,and to ensure the high continuity of the user’s real-time high-precision positioning.The main research contents and innovations of the thesis are as follows:(1)The accuracy and continuity of the real-time precision clock correction and orbit based on SSR on the user side are analyzed,and the influence of the delay on the real-time precision clock correction and orbit is analyzed.In terms of continuity,the continuity of GPS(Global Positioning System)and BDS(Beidou Navigation Satellite System)SSR data is 97%,and the continuity of some GPS and BDS satellites is less than 85%.The reason why users cannot obtain fully continuous real-time SSR products is obtained.In terms of accuracy,the real-time precision clock correction and orbit accuracy of GPS and BDS is within 0.1m,0.35ns,0.2m and 0.8ns respectively.Finally,the influence of the increase of SSR delay on the product accuracy is analyzed from the clock correction and orbit accuracy itself.The results show that with the continuous increase of SSR delay within 0min to 30min,the maximum divergence speed of GPS and BDS in the three directions of R,A,and C can reach 2.4cm/min and 3.4cm/min,respectively.The errors can reach sub-meter and meter levels respectively.Therefore,the SSR delay caused by the unstable communication environment and product continuity will threaten the positioning of high-precision real-time users.(2)Aiming at the problem of PPP positioning accuracy degradation caused by SSR delay and interruption,a real-time precision clock correction prediction method suitable for the user side is proposed.Compared with the traditional clock correction prediction method,this method only needs 1 hour short segment fitting arc length to maintain ns level highprecision clock correction prediction.Aiming at the problem that the prediction model is ill posed due to the jump of SSR clock correction at the Client,a jump point prediction deviation removal method is proposed,which can monitor and process the jump in real-time clock correction data in real time,and improve the impact of SSR product clock correction jump on the prediction model.The results show that the proposed clock correction prediction method and orbit replacement scheme can effectively maintain the decimeterlevel positioning accuracy of real-time precise point positioning when SSR is interrupted.(3)In terms of design and implementation of RT-PPP positioning software,aiming at the problem of decreased positioning continuity under SSR data interruption during the RTPPP process of the existing software,this paper is based on the Windows Qt development environment,implements the proposed method in C++,The RT-PPP processing software is designed from modules of data reception,analysis,processing,result display and storage.Realize GPS/BDS real-time positioning,result display,positioning result output and accuracy comparison functions.The actual test results show that the positioning accuracy of the decimeter level can be achieved,and the positioning requirement of the decimeter level can be maintained during the SSR data interruption within 30 minutes.