satellite based augmentation system (navigation) (SBAS)
A Satellite Based Augmentation System (SBAS) is a satellite-based navigation system that increases the positioning and navigation accuracy of the known navigation satellites, the GPS system, Glonass and Galileo.
There are several incompatible systems: European Geostationary Overlay Service( EGNOS) of the Europeans, Wide Area Augmentation System( WAAS) of the Americans, System for Differential Correction and Monitoring (SDCM) of the Russians and Multi-Functional Satellite Augmentation System( MSAS) of the Asians.
All systems improve the positioning accuracy of satellite navigation systems by a factor of about ten. To increase positioning accuracy, the systems use multiple geostationary satellites and many precisely positioned receiving stations, Ranging and Integrity Monitor Station( RIMS), through which errors in satellite orbits and interference from the ionosphere are converted into correction signals that improve positioning by the GPS system or the other systems.
The increased positioning accuracy is needed in aeronautical applications, especially during landing approaches and in poor visibility. There are also special SBAS modules for positioning, land surveying, agriculture and recreational activities.