Garmin GPSMAP 498C Owner's Manual - Page 104
What is WAAS/EGNOS?, in North America. In Europe, WAAS is referred to as EGNOS. - gpsmap 498 won t find satellites
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APPENDIX > WHAT IS WAAS/EGNOS? What is WAAS/EGNOS? The 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 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. 96 GPSMAP 392/398/492/498 Owner's Manual