WAAS stands for Wide Area Augmentation System. It's a system of satellites and ground stations that provide GPS signal corrections, giving position accuracy up to five times better. A WAAS-capable receiver can give you a position accuracy of better than three meters, 95 percent of the time. You don't have to purchase additional receiving equipment or pay service fees to use WAAS.

European availability

WAAS satellite coverage is available only in North America. Other governments are developing similar satellite-based differential systems - Europe's system is the Euro Geo-stationary Navigation Overlay Service (EGNOS). WAAS receivers are compatible with EGNOS.

The origins of WAAS

The Federal Aviation Administration (FAA) and the Department of Transportation are developing the WAAS program for aviation use. WAAS corrects for GPS signal errors and provides integrity information about each satellite, making positioning information more accurate and more reliable.

How it Works

Ground reference stations monitor GPS satellite data, and master stations collect data from the reference stations and create a GPS correction message accounting for GPS satellite orbit and clock drift plus signal delays caused by the atmosphere. The corrected differential message is then broadcast through geo-stationary satellites (satellites with a fixed position over the equator). Any WAAS-enabled GPS receiver can read the signal.