EGNOS Passes Flight Approach Trials

The new European satellite navigation service dubbed the European Geostationary Navigation Overlay Service or EGNOS has passed its initial series of air traffic flight trials. EGNOS is the first stage of the global navigation satellite system (GNSS) and a precursor to Galileo, the full global satellite navigation system currently under development in Europe. The French regulator DGAC has recently tested and validated the EGNOS signals by comparing the satellite-guided final approach phase with approaches made by using the traditional Instrument Landing System (ILS). EGNOS provides a precision of better than two meters, compared to 15 to 20 meters for the Global Positioning System (GPS) alone. For landing approaches, raw GPS data cannot be used. Airplanes still have to use ILS systems (Instrument Landing Systems) if visibility is poor. However the installation and maintenance of ILS systems at each and every airport is prohibitively expensive. With satellite-based augmentation systems (SBAS) such as EGNOS, CAT I approaches (limited visibility) will be possible without an ILS. For CAT III approaches (zero visibility) even the SBAS will not suffice and ILS are still required. EGNOS is similar to WAAS (Wide Area Augmentation System) which is a satellite-based differential GPS system (DGPS ). The difference is that no additional long-wave receiver is necessary to receive the correction data and there is no need for an endless number of DGPS beacons that transmit these correction data. Systems that are equivalent to EGNOS have been set up in the United States, Japan and India. In principle all three systems are the same and even more astonishing, the three systems are compatible with each other. WAAS is maintained by north America, EGNOS is maintained by the European community and MSAS (Multi-Functional Satellite Augmentation System) is being developed by Japan and other Asiatic countries. EGNOS is a joint venture of the European Space Agency (ESA), the European Commission (EC) and Eurocontrol, the European Organization for the Safety of Air Navigation.