The European Geostationary Navigation Overlay Service (EGNOS) is a satellite based augmentation system developed by the European Space Agency (ESA), the European Commission and EUROCONTROL.
The EGNOS system provides additional signals to users of satellite navigation services, broadcast through geostationary satellites, guaranteeing the integrity of satellite navigation so that it can be used in support of safety-of-life services such as civil aviation.
It supplements the GPS, GLONASS and Galileo systems by reporting on the reliability and accuracy of the positioning data. The official start of operations was announced by the European Commission on 1 October 2009.
According to specifications, horizontal position accuracy should be better than seven metres. In practice, the horizontal position accuracy is at the metre level. The EGNOS system consists of three geostationary satellites and a network of ground stations.
The system started its initial operations in July 2005, showing outstanding performances in terms of accuracy (better than two metres) and availability (above 99%); and it was certified for use in safety of life applications in March 2011. An EGNOS Data Access Service is also available since July 2012.
Similar service is provided in North America by the Wide Area Augmentation System (WAAS), and in Asia, notably Japan, by the Multi-functional Satellite Augmentation System (MSAS).