Plain English Meaning

WAAS is an add-on to GPS that makes the position information much more accurate and trustworthy. It does this by checking GPS signals from ground stations, working out the small errors, and sending corrections up to the aircraft through a satellite. With WAAS, a GPS receiver is precise enough to fly approaches that bring the aircraft down close to the runway with vertical guidance, similar to an ILS.

Full Definition

A satellite-based augmentation system that improves the accuracy, integrity, and availability of GPS signals across North America. WAAS uses a network of ground reference stations to monitor GPS signals, calculate , and those corrections to aircraft via geostationary satellites. The result is GPS position information accurate enough to support precision-like with vertical guidance down to .