European Geostationary Navigation Overlay Service for aircraft navigation

The first pillar of Europe's navigation programme, the European Geostationary Navigation Overlay Service (EGNOS) – operational since 2009 – is an overlay system based on a network of ground stations and three geostationary satellites. The stations gather data on the current accuracy of GPS signals and embed it in the EGNOS signal, which is uplinked to the satellites to be transmitted to users. EGNOS serves to sharpen the accuracy of GPS signals across Europe and informing users about the current reliability level of the system. Designed against global standards set by the International Civil Aviation Organisation (ICAO), EGNOS began offering its Open Service for non-safety-of-life uses in October 2009, with its Safety-of-Life Service becoming available for aircraft navigation (allowing vertical guidance for landing approaches) in March 2011.