Waas And Dgps; What Is Waas; What Is Differential Gps (Dgps) - Garmin 3200 Application Manual

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WAAS and DGPS

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 (see "DGPS" below). At

this time the system is still in the developmental stage with a goal of

providing reliable signals with an accuracy of 7 meters (21–22 ft.) both

horizontally and vertically 95% of the time. Current tests have shown

the actual accuracy to be on the order of 2–3 meters. For more informa-

tion, go to http://gps.faa.gov/Programs/WAAS/waas.htm.

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.

In addition to compensating for errors in the position, these correc-

tions signals can also correct for deliberate degradation of the accuracy of

GPS by the U.S. Department of Defense under their Selective Availability

(SA) program. 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.

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