Garmin gpsmap 292 Manuale Utente

A

PPENDIX

 > 

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 292/298 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

.