European Geostationary Navigation Overlay Service
The European Geostationary Navigation Overlay Service (EGNOS) is a satellite based augmentation system (SBAS) developed by the European Space Agency, the European Commission and EUROCONTROL. 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 four geostationary satellites and a network of ground stations.
The system started its initial operations in July 2005, with accuracy better than two metres and availability above 99%; it was certified for use in safety of life applications in March 2011. An EGNOS Data Access Service became available in July 2012.
On 2009, the European Commission, owner of the programe, announced it had signed a contract with the company European Satellite Services Provider, to run EGNOS. As of July 2005, EGNOS has been broadcasting a continuous signal, and at the end of July 2005 the system was again used to track cyclists in the Tour de France road race.
Initial work to extend EGNOS coverage to the Southern Africa region is currently being undertaken.
Similar to WAAS, EGNOS is mostly designed for aviation users which enjoy unperturbed reception of direct signals from geostationary satellites up to very high latitudes. The use of EGNOS on the ground, especially in urban areas, is limited due to relatively low elevation of geostationary satellites: about 30° above horizon in central Europe and much less in the North of Europe. To address this problem, ESA released in 2002 SISNeT, an Internet service designed for continuous delivery of EGNOS signals to ground users. The first experimental SISNeT receiver was created by the Finnish Geodetic Institute. The commercial SISNeT receivers have been developed by Septentrio.
|Satellite Name & Details||NMEA / PRN||Location|
|Inmarsat 3-F2 (Atlantic Ocean Region-East)||NMEA #33 / PRN #120||15.5°W|
|ARTEMIS||NMEA #37 / PRN #124||21.5°E|
|Inmarsat 4-F2 (Europe Middle East Africa)||NMEA #39 / PRN #126||25°E|
|Inmarsat 3-F1 (Indian Ocean)||NMEA #44 / PRN #131||64.5°E|
|Astra 4B (a.k.a. Sirius 5 or SES-5) ||launch in 2012||5.0°E|
|Astra 5B ||launch in 2013||31.5°E|
Ground stations 
More than 40 ground stations are linked together to create EGNOS network which consists:
- 34 RIMS (Ranging and Integrity Monitoring Stations): receiving signals from US GPS satellites,
- 4 MCC (Mission Control Centers): data processing and differential corrections counting,
- 6 NLES (Navigation Land Earth Stations): accuracy and reliability data sending to three geostationary satellite transponders to allow end-user devices to receive them.
There are plans to develop EGNOS-based landing aids for airliners.
- EGNOS ‘Open Service’ available: a new era for European navigation begins today
- "EGNOS navigation system begins serving Europe’s aircraft". Archived from the original on 2011-03-03. Retrieved 2011-03-03.
- "EGNOS Service Extension to Southern Africa".
- "Airbus transporters to be equipped for satellite landings". 2011-05-13. Retrieved 2011-11-22.
- European Commission information on EGNOS
- EGNOS Portal for application developers
- Website of the EGNOS operator ESSP SaS
- EGNOS Operations User Support
- ESA information on EGNOS
- The EGNOS book, ESA Publications, Javier Ventura-Traveset and Didier Flament
- European Space Agency information on EGNOS for Professionals
- Learning EGNOS
- ESESA - EGNOS Service Extension to South Africa
- Usman A Zahidi, "EGNOS enabled GPS Software Receiver" Report Page, 
- Information on WAAS, EGNOS & MSAS