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GPSMAP 76 Owner’s Manual 61
APPENDIX > WAAS AND DGPS
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 correction data
as determined by ground reference stations. WAAS
testing completed in September of 2003 confirmed
an accuracy of 2 to 3 vertical meters throughout the
majority of the continental U.S. and portions of Alaska.
For more information, go to
http://gps.faa.gov/Programs/WAAS/waas.htm
NOTE: If you are using the GPSMAP 76 outside
of the U.S., it is recommended that you turn off
WAAS for the most accurate location fix.
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.