Garmin GPSMAP 198C Sounder - Manual (Page 109)

GPSMAP 198C Sounder Owner’s Manual 103
A
PPENDIX
> W
HAT IS A
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 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 198C Sounder outside
of the U.S.A., we recommend 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.
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.