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Appendix
What is WAAS?
The Wide Area Augmentation System (WAAS) is an F.A.A. funded project to improve the overall
integrity of the GPS signal. It is a space-based system that broadcasts integrity information and correc-
tion data as determined by ground reference stations (see below). Current tests have shown the actual
accuracy to be on the order of 2–3 meters. For more information, go to http://gps.faa.gov/Programs/WAAS/
waas.htm.
NOTE: If you are using the GPSMAP 276C outside of the U.S.A., it is recommended that you
turn off WAAS for the most accurate location fi x.
What is Differential GPS (DGPS)?
The U.S. and Canadian governments (among others) have set up Differential GPS ( DGPS) stations to
transmit correction signals. They are operational in coastal areas and on many navigable river systems.
The DGPS system is available for use without a fee.
Please refer to the U.S. Coast Guard’s web site: http://www.navcen.uscg.gov/ for locations and the status
of the differential sites. Using DGPS requires additional equipment.
WAAS and DGPS
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