What's New

On September 2007, Wide Area Augmentation System (WAAS) coverage was expanded into Canada and Mexico. This achievement was made possible by the integration of nine new international wide-area reference stations (WRS) into the WAAS network. In addition to extending WAAS coverage to users throughout large portions of Canada and Mexico, this expansion also benefits the U.S. WAAS users within the U.S., formerly on the fringes of WAAS coverage, are now well within its coverage boundaries. The new WRSs are located in Canada (Goose Bay, Gander, Winnipeg, and Iqaluit) and in Mexico (Mexico City, Puerto Vallarta, Mérida, Tapachula, and San Jose del Cabo).

What is WAAS?

  You've heard the term WAAS, seen it on packaging and ads for Garmin products, and maybe even know it stands for Wide Area Augmentation System. Okay, so what the heck is it? Basically, it's a system of satellites and ground stations that provide GPS signal corrections, giving you even better position accuracy. How much better? Try an average of 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. And you don't have to purchase additional receiving equipment or pay service fees to utilize WAAS.

The origins of WAAS

  WAAS consists of approximately 35 ground reference stations positioned across North America that monitor GPS satellite data. Two master stations, located on either coast, collect data from the reference stations and create a GPS correction message. This correction accounts 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, or satellites with a fixed position over the equator. The information is compatible with the basic GPS signal structure, which means any WAAS-enabled GPS receiver can read the signal.

Who benefits from WAAS?

  Currently, WAAS satellite coverage is only available in North America. There are no ground reference stations in South America, so even though GPS users there can receive WAAS, the signal has not been corrected and thus would not improve the accuracy of their unit. For some users in the U.S., the position of the satellites over the equator makes it difficult to receive the signals when trees or mountains obstruct the view of the horizon. WAAS signal reception is ideal for open land and marine applications. WAAS provides extended coverage both inland and offshore compared to the land-based DGPS (differential GPS) system. Another benefit of WAAS is that it does not require additional receiving equipment, while DGPS does.

  Other governments are developing similar satellite-based differential systems. In Asia, it's the Japanese Multi-Functional Satellite Augmentation System (MSAS), while Europe has the Euro Geostationary Navigation Overlay Service (EGNOS). Eventually, GPS users around the world will have access to precise position data using these and other compatible systems.

It just Keeps Getting Better

100 meters: Accuracy of the original GPS system, which was subject to accuracy degradation under the government-imposed Selective Availability (SA) program. 15 meters: Typical GPS position accuracy without SA. 3-5 meters: Typical differential GPS (DGPS) position accuracy. < 3 meters: Typical WAAS position accuracy. All information from Garmin and FAA sources .

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