Research On GNSS Integrated Point Positioning And Quality Control

With the development of global navigation satellite system(GNSS)and the gradual improvement of BDS and Galileo system,navigation and positioning technology is moving towards real-time,high precision and multi-GNSS integration.Precise point positioning,as one of the GNSS high precision positioning technology,has been widely used in various fields.Due to the small number of visible satellites and the weak spatial geometric distribution,single-system PPP has a long convergence time and a low accuracy of short-term positioning.While as the number of satellites of integrated system increase,the geometric configuration of satellite space can be improved,which is helpful to accelerate the convergence of PPP and improve the positioning accuracy.But for the low precision navigation of SPP(Standard Point Positioning),too much observation information of integrated system puts forward higher requirements on receiver and increases the navigation positioning computation,resulting poor real-time performance.At the same time,because of different measuring accuracy and gross error probability increasing of Multi-GNSS integrated PPP,and the Kalman filter without robustness,the dynamic positioning results are easy to diverge.In view of the above problems,this paper studies the satellites selection algorithm of GNSS integrated navigation and positioning precision,PPP ambiguity resolution and multi-GNSS integrated PPP and adaptively robust Kalman filtering.The main work and conclusions are as follows:First,in view of the problem that the redundant observations and the large amount of calculation are caused by too many visual satellites,as well as different accuracy of observations of the integrated system,based on the performance evaluation index of satellite navigation positioning GDOP and Quasi-optimal satellite selection algorithm,this paper presents a step-by-step weighted satellite selection algorithm for GPS/GLONASS/BDS integrated navigation and positioning system.And based on the robust Helmert variance components,the accuracy and reliability of GPS/GLONASS/BDS system integrated navigation and positioning are analyzed.Second,aiming at the slow convergence rate of PPP and need long time observation to achieve high-precision positioning,a PPP ambiguity resolution method based on un-difference FCBs estimation is studied,and a quality control method for optimizing FCBs estimation and ambiguity resolution is proposed.The experimental results show that the PPP ambiguity resolution can effectively improve the accuracy of PPP in a short time and shorten the convergence time.Third,the GPS/GLONASS/BDS/Galileo multi-system integrated PPP is researched and analyzed,including the G/R/E/C?G/R/E?G/RC?R/E/C?G/R?G/E?G/C?R/E?R/C integrated system PPP positioning effect and difference between single-system PPP.The results show that the multi-system positioning effect is better than that of single-system,which can speed up PPP convergence and improve the positioning accuracy,and the one day positioning effect of G/R/E/C,G/R/E,G/R/C and G/R is close.Forth,the adaptively robust Kalman filtering algorithm is introduced to Multi-GNSS combination PPP,based on the accuracy of the observation of the integrated system and the characteristics of the PPP parameters,the PPP equivalent weight factor and the adaptive factor selection method are given,the effect of adaptively robust Kalman filtering in static and dynamic integrated system is analyzed and discussed.The experimental results show that the adaptively robust Kalman filtering can not only resists the observations and dynamic model anomalies,but also improves the positioning accuracy and the convergence speed of PPP.