GPS World, March 2010

Multi GNSS Receivers PROFESSIONAL OEM s the same satellite because the precise orbits and clocks are calculated from a global network of reference stations As a result PPP gives a highly redundant and robust position solution The results presented here represent a significant step forward in PPP GNSS research and development Using GLONASS improves the availability and reliability of the solution The G2 systems horizontal positioning accuracy is at the decimeter level These results derive from increasing the number of satellites in the constellation by 60 percent from about 30 to 50 satellites The outcome of the development of the G2 real time combined GPS and GLONASS PPP service represents a next generation GNSS augmentation Fur ther the later GLONASS M satellites have improved performance and lifetime over previous GLONASS satellites so that results will continue to improve as that constellation is replenished G2 development has benefited from the close cooperation between Fugro and the European Space Operation Centre ESOC an establishment of the European Space Agency ESA ESOC has contributed its long experience and expertise on precise orbit and clock processing techniques while the strength of Fugro is real time positioning and navigation services Based on this work Fugro has introduced the first real time GPS and GLONASS precise orbit and clock service The service utilizes Fugros own network of dual system GNSS reference stations to calculate precise orbits and clocks on a satellite by satellite basis for all 50 satellites of the two global navigation satellite systems The system comprises about 40 dual frequency GPS and GLONASS reference stations distributed around the world as shown in FIGURE 1 Raw GNSS measurement data for all satellites are transmitted to processing centers for calculation of the precise orbit and clock of each GPS and GLONASS satellite FIGURE 3 next page The precise data generated is then broadcast to users via geostationary communications satellites with nearly global coverage as shown in FIGURE 2 Inside the end user equipment a dual frequency carrier phase based PPP solution gives horizontal positioning accuracy at the decimeter level The PPP calculation module is provided by Fugro and is embedded in multiple GNSS receiver manufacturers products as well FIGURE 1 The G2 reference station network consists currently of 40 GNSS receivers owned and operated by Fugro FIGURE 2 The G2 precise orbits and clocks are broadcast over redundant geostationary satellite beams together with the other Fugro services www gpsworld com March 2010 GPS World 29