ION GNSS 2012
Session E6: Precise Point Positioning 2

Title: Evaluation of European Real-Time Ionospheric Delay for Precise Point Positioning (PPP) Service
Author(s): H. Zhang, Wuhan University, China; M. Ge, X. Li, R. Tu, T. Nischan, S. Klose, J. Wickert, German Research Centre for Geosciences, Germany
Room: 209/210 (NCC)

Currently, GFZ has developed a demo system for real-time Precise Point Positioning (PPP) service under the call-for participation of IGS Real-Time Pilot Project. Real-time GPS satellite clock, Uncalibrated Phase Delay (UPD), Ionospheric mapping and the user-end PPP algorithm are developed and testing online now. Unlike traditional PPP service, integer-ambiguity characterized after UPD removed in zero-difference carrier-phase observation improve both the positioning accuracy and convergence time. However, due to the accuracy limitation of ionospheric mapping, the real-time centimeter-level PPP convergence time is still a problem. To improve the rapid convergence time, A new algorithm with ionospheric-considered in PPP algorithm and will be reported by Xingxing Li in this ION assembles. However, in dual-frequency PPP rapid convergence, another obstacle is receiver´s Differential Code Bias (DCB), which is coupling with Ionospheric mapping, just as SV orbit and clock error. Existing and inhabited DCB means different receiver clock error in C1, P1 and P2 observations, which make the fact that PPP can not estimate only one clock error while using zero-difference P1 and P2. Based on the fact above, this paper will evaluate both the accuracy of Ionospheric mapping and DCB´s effect on PPP positioning using EUREF real-time data. Preliminary results show that the existing DCB will mostly affect height accuracy of PPP and will improve several decimeters systematic error after receiver´s DCB removed. As to the Real-Time Ionospheric mapping, RMS indicate that the internal precision is about 0.10~0.25meters while polynomial and grid-search and interpolating technique are used together. Its effect on positioning is comparable with the post-processed GIM products. More results are in preparation for detail analysis.

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