What Is Waas/Egnos - Garmin GPSMAP 392, 398, 492, 498 Owner's Manual

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What is WAAS/EGNOS?

he Wide Area Augmentation System (WAAS) is an FAA funded
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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.
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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 392/398/492/498 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.
For more information, go to http://gps.faa.gov.
GPSMAP 392/398/492/498 Owner's Manual