A Study On GPS Precise Point Positioning Data Processing

Precise Point Positioning (PPP) is an approach that uses un-differenced pseudo-range and carrier phase observations along with IGS precise orbit and satellite clocks, for stand-alone precise geodetic point positioning (static or kinematic) with centimeter precision. Because this approach need only one GPS receiver and can obtain the receiver coordinate without any reference stations. So It provides a very efficient way to access the terrestrial reference frame or LEO's orbit determination, wide area precise positioning and navigation. Also it is the key technique to realize the Global RTK and the international based differential GPS positioning in the future.This paper is focus on the data processing of Precise Point Positioning, the principle of Precise Point Positioning is introduced and the models of Precise Point Positioning are investigated, there are the Traditional model, The UofC model and the Ambiguity-free model. Detailed analyses and discusses are made to the three models. In order to obtain more accuracy of PPP, all kinds of errors in PPP are argument and the corresponding solutions are given in this paper.The IGS orbit information is currently at 15-minute intervals and the IGS clock information are provided as two kinds—the kind of 15 minute intervals and the one of 5 minute intervals .However, the interval of epoch in observation data may far least than these value. In this paper three methods are applied to interpolate Precise Ephemeris and Clock Off set. Detailed analyses and discusses are made to them. In the data Pre-processing of PPP, Melbourne-Wiibbena combinations is usestogether with L_I combinations, andφ^1,-1,φ_-7,9 combinations are used with LC combinations to detect and repair the cycle slip. And then smoothing Pseudo-range with carrier Phase and calculate the initial Ambiguity parameters. unknown parameters of un-difference observation equations are estimated with least square approach. Finally, a program of GPS Precise Point Positioning is compiled by the author, experiments conducted in practice and the result are analysis in this paper.