Performance Analysis And Research On GNSS Precise Positioning With Time Delay

Precise point positioning and relative positioning are widely used in practical research and engineering projects because they can provide centimeter-level positioning.However,due to the limitation of communication network delay,product technology level and other factors in practical application,there is always time delay in data transmission,which affects the accuracy and efficiency of positioning.In view of this,this paper aims to study the impact of time delay caused by network and communication on real-time PPP and RTK positioning,so as to improve the accuracy and efficiency of real-time PPP and RTK positioning.Focusing on this research objective,this paper first briefly introduces the PPP and RTK positioning model,parameter estimation method,error sources affecting GNSS positioning accuracy and corresponding processing measures in PPP and RTK,the observation quality of GPS,GLONASS,BDS and Galileo satellite signals was analyzed from the aspects of visible satellite number,PDOP value,signal-to-noise ratio and multi-path.Finally,the influence of time delay on real time PPP and RTK positioning is analyzed and studied.Research contents and relevant conclusions mainly include the following aspects:1)Summarizes the research hotspot of PPP and RTK at home and abroad,and according to the research content of this paper,expounds the research status of real-time PPP and asynchronous differential positioning considering time delay from domestic and foreign scholars;2)Reviews the positioning theory of PPP and RTK.It covers the spatiotemporal datum and its transformation including GPS,GLONASS,BDS and Galileo,GNSS observation equation and common combination observation PPP and RTK positioning model,recursive least squares estimation and kalman filter,common error sources and corresponding processing measures in GNSS data processing,etc;3)Analyzes the service performance and signal quality of GPS,GLONASS,BDS and Galileo and their combined systems in Asia Pacific and non-asia Pacific regions.It includes the number of visible satellites,PDOP value,signal-to-noise ratio,multi-path,etc.At the same time,the simulation experiment of cycle jump detection and repair is carried out by using MW combination and GF combination;4)Analyzes the deviation between the real-time precision orbit and clock error of CNES analysis center and the post-event precision orbit and clock error of GFZ.It is found that the real-time orbital deviation of BDS is larger than that of other systems,and the real-time orbital deviation of BDS GEO satellite can even reach 3-5m.The effect of time delay on real time PPP is mainly studied by post-simulation time delay method.The results show that time delay has a great influence on the positioning accuracy and convergence time of real time PPP.5)Briefly introduces the principle and error analysis of asynchronous RTK positioning,and compares the differences between asynchronous RTK and classical synchronous RTK.Analyzed the GPS,GLONASS,BDS and Galileo satellite clock difference under time delay after the magnitude of change,compared the affected by the same time,considering the influence of time delay asynchronous RTK and ignore the time delay the classic RTK positioning result difference,asynchronous RTK model is superior to the classic RTK model and BDS and Galileo asynchronous RTK positioning precision is higher than that of GPS and GLONASS.Then,the orbit delay and clock delay errors caused by GPS,GLONASS,BDS and Galileo satellites under the same time delay are evaluated and compared.The results show that compared with GPS and GLONASS satellites,the time delay has less influence on the orbit delay and clock delay errors of BDS and Galileo.Finally,a height angle stochastic model considering SISRE was proposed for multi-GNSS asynchronous RTK.The experimental results showed that,at the difference age of 30 s,the height angle stochastic model considering SISRE was 11.6%,16.7% and 10.0% higher in the direction of E,N and U than the traditional height angle stochastic model,The results of GRCE system were improved by 23.9%,25.2% and 18.5%in the directions of E,N and U,respectively.