What is SBAS and GBAS?
WAAS, EGNOS, MSAS, SNAS, GAGAN, GPS-C and StarFire are SBAS (Satellite Based Augmentation Systems). SBAS capability allows for accuracy to within three meters (or less) most of the time. StarFire even down to few centimeters all over the world. dGPS and LAAS are GBAS (Ground Based Augmentation Systems) and they are based on local correction broadcasts.
WAAS is available in North America, GPS-C in Canada, EGNOS in Europe, MSAS in Asia and GAGAN in India. SNAS is proposed by China. StarFire works all over the world and is very accurate, typically 4.5 cm, but it requires more complex receivers.
All above mentioned SBAS systems use additional satellites to correct the GPS signal. Without corrective signals the GPS is less accurate.
WAGE is an improvement of the original military GPS signal and is available all over the world but only for the GPS encrypted P(Y) Code.
dGPS and LAAS are similars as those mentioned but they use local ground stations to send corrections (GBAS).
Additional Information:SBAS GBAS
Related or Similar Systems: