Precision navigation in European skies

A global system of air traffic control based entirely on global positioning systems, an inevitable idea that has been inching toward realization for more than a decade, came closer on 6 June, with the first transmission of test signals from the European Geostationary Navigation Overlay Service (Egnos). The point of Egnos is to provide error correction to geopositioning signals, relying on dedicated equipment installed on three geostationary satellites and a network of ground reference stations, so that locations can be determined at an accuracy of close to 1 meter. For now, Egnos will error-correct signals from the US Global Positioning System (GPS) and Russia´s Global Navigation Satellite System (Glonass). Eventually, though, the expectation is that it will error-correct signals from Europe´s own constellation of global positioning satellites, dubbed Galileo. Galileo will rely on 30 low-earth-orbiting satellites, together with ground stations, and is expected to begin transmitting its first test signals in 2006.