WAAS, EGNOS, MSAS and GLONASS
The rest of the world were not going to let the Americans have it all their own way, and so other systems were developed around the world.
In answer to the US military, the Russian military established their GLONASS system (Global Orbiting Navigation Satellite System)
As an aid to navigation, non-military systems were also developed, which correct the errors of the military systems.
WAAS (Wide Area Augumentation System) is maintained by North America.
MSAS (Multifunctional Satellite Augumentation System) is developed by Japan and other Asiatic countries.
EGNOS European Geostationary Navigation Overlay Service is maintained by the European Commission, the European Space Agency and the European Organisation for the Safety of Air Navigation.
In principle, all systems are the same and even more astinishing, the systems are compatible to each other.
For obvious reasons, EGNOS is of more interest to us in this part of the world, and it entered its pre-operational phase in 2006. It is Europe's first activity in the field of global navigation satellite system, and is a precursor to Galileo, the full global navigation system under development in Europe. Consisting of three geostationary satellites and a network of ground stations, EGNOS achieves its aim by transmitting a signal containing information on the reliability and accuracy of the positioning signals sent out by the American GPS system and the Russian GLOSNASS system. It allows users in Europe and beyond to determine their position to within 2 metres.
By the way, with all the error correction satellites going up, there seemed little sense in the Americans continuing their 'Selective Ability' built in error, so as of 1st May, 2000, it was discontinued, and the GPS error now ranges around the 20 metre mark.
We are glad to report that the Irish Homing Union Differential GPS system in operation uses EGNOS, and we believe our calculations to be accurate to a metre of even less.