Garmin GPSMAP 76Cx Owner's Manual

Also see for GPSMAP 76Cx: Owner's manual Declaration of conformity Quick reference guide Guide de l'utilisateur

Contents

Garmin GPSMAP 76Cx Owner's Manual Manual pdf 92 page image

82 GPSMAP 76Cx Owner’s ManualAPPENDIX > WHAT IS WAAS/EGNOS?What is WAAS/EGNOS?The Wide Area Augmentation System (WAAS) is anFAA funded service to improve the overall integrity ofthe GPS signal for users in North America. In Europe,WAAS is referred to as EGNOS.The system is made up of satellites and approximately25 ground reference stations positioned across theUnited States that monitor GPS satellite data. Twomaster stations, located on either coast, collect datafrom the reference stations and create a GPS datacorrection message.According to the FAA’s Web site, testing of WAAS inSeptember 2002 confirmed an accuracy performanceof 1-2 meters horizontal and 2-3 meters verticalthroughout the majority of the continental UnitedStates and portions of Alaska.WAAS is just one service provider that adheres to theMOPS (Minimum Operational Performance Standard)for global Satellite Based Augmentation Systems(SBAS). Eventually there will be several services ofworldwide geostationary communication satellitesthat broadcast integrity information and differentialcorrection data as transmitted by ground referencestations.All SBAS systems use the same receiver frequency;therefore any operational SBAS system should becapable of providing your GPS unit with increasedaccuracy at any location in the world.Currently, enabling WAAS on your GPSMAP 76Cx inregions that are not supported by ground stations, maynot improve accuracy, even when receiving signalsfrom an SBAS satellite. In fact it can degrade theaccuracy to less than that provided by GPS satellitesalone. For this reason, when you enable WAAS onyour Garmin GPS receiver, the receiver automaticallyuses the method that achieves the best accuracy. Toenable or disable WAAS, see page 57.For more information, go to http://gps.faa.gov.