wide-area augmentation system
Wide-Area Augmentation System
[¦wīd ¦er·ē·ə ȯg·mən′tā·shən ‚sis·təm]wide-area augmentation system (WAAS)
WAAS is based on a network of approximately 35 ground reference stations located in the Continental United States. Each of these reference receivers is precisely surveyed, enabling each to determine any error in the GPS signal being received at the station. The error is then fed to the master station computer which calculates correction algorithms and assess the integrity of the entire GPS system. The data is then up linked to a communication satellite in a geostationary orbit. This communication satellite forwards the correction signal to the aircraft's GPS receiver. The aircraft receiver then makes necessary adjustments to provide improved positioning accuracy. The communication satellites also act as GPS navigation satellites, thus adding to the number of satellites in the GPS constellation.