The European geostationary navigation overlay system (EGNOS) is a satellite navigation system under development by the European Space Agency, the European Commission and EUROCONTROL. It is intended to supplement the GPS and GLONASS systems by reporting on the reliability and accuracy of the signals, allowing position to be determined to within 2 metres. It will consist of three geostationary satellites and a network of ground stations and is intended to be operational in 2004. It is planned as a precursor to the Galileo positioning system.
Similar service is provided in America by the WAAS system.
