Garmin GPSMAP 76CSx User Manual

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PPENDIX

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W

HAT

 

IS

 WAAS/EGNOS?

T

he Wide Area Augmentation System (WAAS) is an 

FAA funded service to improve the overall integrity of 

the GPS signal for users in North America. In Europe, 

WAAS is referred to as EGNOS.
The system is made up of satellites and approximately 

25 ground reference stations positioned across the 

United States that monitor GPS satellite data. Two 

master stations, located on either coast, collect data 

from the reference stations and create a GPS data 

correction message.
According to the FAA’s Web site, testing of WAAS in 

September 2002 confirmed an accuracy performance 

of 1-2 meters horizontal and 2-3 meters vertical 

throughout the majority of the continental United 

States and portions of Alaska.
WAAS is just one service provider that adheres to the 

MOPS (Minimum Operational Performance Standard) 

for global Satellite Based Augmentation Systems 

(SBAS). Eventually there will be several services of 

worldwide geostationary communication satellites 

that broadcast integrity information and differential 

correction data as transmitted by ground reference 

stations. 
All SBAS systems use the same receiver frequency; 

therefore any operational SBAS system should be 

capable of providing your GPS unit with increased 

accuracy at any location in the world.
Currently, enabling WAAS on your GPSMAP 76CSx 

in regions that are not supported by ground stations, 

may not improve accuracy, even when receiving 

signals from an SBAS satellite. In fact it can degrade 

the accuracy to less than that provided by GPS 

satellites alone. For this reason, when you enable 

WAAS on your Garmin GPS receiver, the receiver 

automatically uses the method that achieves the best 

accuracy. To enable or disable WAAS, see 

.

For more information, go to 

http://gps.faa.gov/

Programs/WAAS/waas.htm

.