ION GNSS 2012
Session E6: Precise Point Positioning 2

Title: SBAS-based Single and Dual Frequency Precise Point Positioning (PPP)
Author(s): L. Wanninger, A. Hesselbarth, Dresden University of Technology, Germany
Date/Time: Friday, September 21, 2012, 4:26 p.m.
Room: 209/210 (NCC)

The quality of real-time GPS positions based on the method of Precise Point Positioning (PPP) heavily depends on the availability and accuracy of satellite orbit and satellite clock corrections. Satellite Based Augmentation Systems (SBAS) provide these corrections but they are actually intended to be used for wide-area differential GPS (WADGPS) with positioning results on the 1 m accuracy level. Nevertheless, SBAS-based carrier-phase PPP is able to achieve much more accurate positioning results. We applied SBAS corrections for static and kinematic PPP and are thus able to compare the PPP performance of the North-American Wide Area Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS), and the Japanese Multi-functional Satellite Augmentation System (MSAS).
PPP data processing using SBAS corrections differs slightly from those using orbit and clock products of the International GNSS Service. Differences exist with respect to the orbit reference point at the satellites, the geodetic datum of the orbit data, and the kind of code delays which affect the clock corrections. We extended our WaPPP post-processing software accordingly, so that we were able to compare SBAS-based PPP results with IGS-PPP-results.

We processed more than 100 days of observation data from 34 continuously operating reference stations (CORS) from North America, Europe, and Japan in static and kinematic mode. Among the 3 existing SBAS, the by far best results of dual frequency PPP were achieved for WAAS: horizontal and vertical position accuracies were considerably smaller 10 cm for static 24 h observation data sets and smaller 30 cm for kinematic observations. The European Geostationary Navigation Overlay Service (EGNOS) and the Japanese Multi-functional Satellite Augmentation System (MSAS) yield positioning results with biases of several 10 cm and variations larger by factors of 2 to 4 as compared to WAAS.

Single frequency SBAS-based PPP uses the ionosphere corrections provided by the particular SBAS. We implemented the application of these corrections to single frequency code and carrier-phase observations and we are now (March 2012) underway to produce single PPP results. Here again, our results to be presented at ION GNSS 2012 will allow a detailed comparison of the PPP performance of the three existing SBAS systems.

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