The new G4 service: multi-constellation Precise Point Positioning including GPS, GLONASS,

In 2009, Fugro launched the G2 service, the first global Precise Point Positioning (PPP) service including GPS and GLONASS constellations.

18 Sep 2015
J. Tegedor, D. Lapucha, O. Ørpen, E. Vigen, T. Melgård, R. Strandli


Making use of a global reference station network, satellite orbits and clocks are computed in real-time and broadcast to users in the field over geostationary satellites, enabling homogeneous decimeter-level accuracy worldwide. The system has been tailored for professional maritime applications requiring a high-level of accuracy and availability. 
With the development of new GNSS systems, such as Galileo and BeiDou, an enhanced G4 service has been introduced in 2015, supporting also the new constellations. G4 supports all BeiDou satellites, including Medium Earth Orbit (MEO), Inclined Geosynchronous Orbit (IGSO) and Geostationary Orbit (GEO) satellites. This is particularly useful in Asia-Pacific area, where the number of BeiDou satellites is enough to achieve continuous BeiDou only positioning. Galileo has also been implemented and will be offered to customers as soon as the system enters the Initial Operational Capability (IOC).
The benefits of adding new constellations to Precise Point Positioning will be described in terms of increased robustness, availability and accuracy. The positioning performance of the system will be presented, with particular focus on interoperability and interchangeable integration of different GNSS systems.
Additionally, real-time BeiDou-only PPP results will be presented, including also using GEO satellites. This is particularly challenging due to lack of geometry variation for geostationary satellites, which has an impact on the orbit accuracy for these satellites. To the knowledge of the authors, this is the first time where GEO satellites have been used in real-time PPP.