Research On The Ionospheric Error In GPS Single-frequency Precise Point Positioning

GPS precise point positioning (abbreviated as PPP) technique is based on precisesatellite orbits and satellite clock error which are calculated in real-time orpost-processing using observations of GPS tracking stations located in the world, andonly using a GPS receiver’s observed received pseudorange and carrier phaseobservations, calculate to get the tested point’s high-precision ITRF coordinates.Because the PPP technology has many advantages, such as convenient、simple、highprecision and so on, it has been the concern of many areas.Currently, GPSdual-frequency PPP already has a mature technology and very high accuracy,and hasbeen widely used in the production practice. But because GPS single-frequency PPPhas fewer observed value, many errors are not very good to eliminate or weaken,particularly ionospheric delay errors, so the GPS single-frequency is a currentresearch focus. The single-frequency precise point positioning research work of thispaper are:First, carry out a systematic expatiation to GPS single-frequency precise pointpositioning, including the establishment of observation equations，observations’combined method，various of error sources and their correction methods, parameterestimation, and so on. Carry out a detailed analysis for the each part, and come upwith the suitable methods for the single-frequency PPP.Second, analyze the basic characteristics of the ionosphere and its effects on GPSsignal propagation, and introduce the traditional classical ionospheric models whichsuit with the single-frequency PPP, including Bent model、IRI model、Klobucharmodel and NeQuick model which Galileo system recommend single user to use.Then, on the base of the previous research, describe the principle of the GPSsingle-frequency observations calculating VTEC (Vertical Total Electron Content) in detail, and list the specific calculation steps, and program to the approach.Last, using single-frequency observations calculate out the CDUTCORS station’sVTEC value in the experimental time period, and the results are compared with theVTEC value which dual-frequency observations calculate out, and are compared withthe VTEC value which are downloaded from the Seismic. Finally, make theevaluation to the method of single-frequency calculating VTEC value.