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1. What is WAAS?
 WAAS stands for Wide Area Augmentation System. It's a system of satellites and ground stations
that provide GPS signal corrections to improve position accuracy to up to 5 times better. A WAAS-capable receiver
can provide a position accuracy of better than three meters 95 percent of the time. WAAS consists
25 ground reference stations positioned across the United States and 2 master stations. The 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 and ionosphere. The corrected differential message is then broadcast
through one of two geostationary satellites (satellites with a fixed position over the equator). Any
WAAS-enabled GPS receiver can read the signal. 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. |
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