Research On The Influence Factors Of Convergence Time Of GPS Precise Point Positioning

With the increasing accuracy of precise satellite orbit and clock products which areprovided by IGS in recent years, and because the accuracy of GPS single point positioningis low，it is unable to realize high precision positioning. And differential GPS positioning isinfluenced by the operating distance, the cost of the instrument and so on, un-differencedprecise point positioning technology has become a research hotspot of global satellitepositioning technology. In recent years, it also has emerged a large number of researchresults. But it is restricted by the following factors. On one hand, convergence time ofprecise point positioning is long so that it can’t be widely spread in engineering applications.On the other hand, precision satellite ephemeris has a response time. It is unable to meet thereal-time requirements of users.This paper discusses and analyzes the problems of precise point positioning whichconvergence time is long. Firstly, we introduce the basic principle of precise pointpositioning briefly. Secondly, the data processing method of precise point positioning isdiscussed. Thirdly, the factors influencing the convergence time of precise point positioninghas been analyzed through experiments and some improvements to reduce the PPPconvergence time are summarized.Based on the analysis of the factors influencing the convergence time of precise pointpositioning (PPP) such as the quality of observation data, the sampling interval, the type ofprecise satellite ephemeris, tropospheric correction method and satellite space geometricconfigurations PDOP, the following useful conclusions are obtained：(1) The type of receivers and the delay deviation of the hardware have little impact onthe convergence time of precise point positioning.(2) For the stations of high latitudes, using troposphere parameters estimation methodnot only can accelerate the convergence time of precise point positioning (PPP), but alsocan greatly improve the accuracy of positioning results. For the stations of middle and lowerlatitudes, the convergence speed and precision of the estimation in X, Y direction is betterthan that of model correction. The convergence speed of parameter estimation and modelcorrection in Z direction are equal. In general, the positioning precision and convergence speed of parameter estimation is much better than the model correction.(3) The sampling interval of observation data are smaller(>1second), the convergencespeed of the positioning result is accelerated. For the observation data of longer time, thesampling interval has a less effect on the convergence rate; for the observation data of shorttime (usually within2h), the sampling interval has a bigger influence on the convergencerate.(4) The satellite geometric dilution of precision PDOP is not only closely related to thenumber of visible satellites, but also to the geometric configuration of satellite constellation.The number of visible satellites is more, the geometric configuration of satelliteconstellation is better, and the value of corresponding PDOP is smaller, and the accuracy ofpositioning is higher, and its convergence speed is faster.