GPS Precise Point Positioning Using Undifferenced Phase Observation

To overcome these shortcomings in differential GPS positioning,a new technique called precise point positioning(PPP) has been developed.In this approach,the IGS precise orbits and satellite clocks are used together with the undifferenced dual-frequency pseudorange and carrier phase observations of one single receiver for precise geodetic point positioning.It provides a very efficient tool to access the terrestrial reference frame or LEO's orbit determination.Also it is the key technique to realize the Global RTK and the internet-based differential GPS positioning in the future.This paper describes the approach of PPP in detail,and then discusses some problems in data processing.Finally,it analyzes the experimental results,which show that the initial time of PPP is about 15 minutes and the accuracy of single epoch positioning can be better than 20cm in X,Y and Z components after initialization.