Wide Area Augmentation System (WAAS)

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The Wide Area Augmentation System (WAAS) is a very precise navigation system that provides the additional accuracy, availability, continuity, and integrity necessary to enable pilots to rely on the Global Positioning System (GPS) for all phases of flight. It provides improved service for considerably less than using conventional land-based navigation aids.

WAAS works by having a network of ground reference stations collecting GPS satellite data. This data is sent through ground communications lines to master stations which calculate corrections to make the data more accurate and insure its integrity. The correction data is broadcast to user aircraft through two or more geostationary satellite communications links. The aircraft use the WAAS signal, in addition to the GPS service to fly area navigation and Localizer Performance with Vertical (LPV) instrument approaches, equivalent to the legacy Instrument Landing System (ILS).

WAAS benefits graphic

Status

The Federal Aviation Administration approved WAAS for aviation use in all weather conditions in July 2003 throughout the continental United States and most of Alaska. Until then, no other navigation system could provide highly precise horizontal and vertical navigation to enable aircraft to fly LPV approaches down to 250 feet in all weather conditions throughout the majority of the national airspace system. In 2006, the FAA completed a technical analysis that showed that WAAS LPV approaches can be safely flown down to 200 feet above the runway at a significant number of airports in the continental United States.

The FAA publishes a minimum of 300 LPV approaches per year. The FAA plans to continue WAAS development in two segments to improve the coverage and reliability of the service.

The next segment of WAAS completes in 2008 and will expand service coverage to all of the continental United States, most of Alaska, and significant regions of Canada and Mexico. After 2008, WAAS will be enhanced to take advantage of new technology provided by the Department of Defense as it builds the next generation of GPS. WAAS LPV instrument procedure production will continue to provide the service at all qualifying runways in the NAS.