Garmin GPSMAP 76CS Owner's Manual

Also see for GPSMAP 76CS: Quick guide Specification sheet Owner's manual

Garmin GPSMAP 76CS Owner's Manual Manual pdf 103 page image

93GPSmap 76CSAppendicesWAAS and DGPSWhat is WAAS?The Wide Area Augmentation System (WAAS) is an F.A.A. fundedproject to improve the overall integrity of the GPS signal. It is a space-based system that broadcasts integrity information and correction data asdetermined by ground reference stations (see DGPS below). At this timethe system is still in the developmental stage with a goal of providingreliable signals with an accuracy of 7 meters (21-22 ft.) both horizontallyand vertically 95% of the time. Current tests have shown the actual ac-curacy to be on the order of 2-3 meters. For more information, go tohttp://gps.faa.gov/Programs/WAAS/waas.htm.What is Differential GPS (DGPS)?The U.S. and Canadian governments (among others) have set upDifferential GPS (DGPS) stations to transmit correction signals. They areoperational in coastal areas and on many navigable river systems. TheDGPS system is available for use without fee.In addition to compensating for errors in the position, these correc-tions signals can also correct for deliberate degradation of the accuracy ofGPS by the U.S. Department of Defense under their Selective Availability(SA) program.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 requiresadditional equipment.