Garmin GPSMAP 3005C - Marine GPS Receiver Owner's Manual

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Contents

GPSMAP 3005C Owner’s ManualAPPendIX > sAtellIte InforMAtIon And whAt Is wAAs/egnos?Satellite InformationSatellite Sky View45°90°Outer ring -the horizonInner ring- 45°above the horizonCenter dot - 90°above the horizonSatellite LocationThe location of each available satellite is shown over two location rings onthe Satellite Information Page. The outer ring represents the horizon, theinner ring represents 45° above the horizon, and the center represents directlyoverhead. When the unit is using a satellite for navigation, the satellite numberis highlighted on the location rings. The unit can display satellite location withNorth or your current track at the top of the display.Satellite Strength Indicator BarsThe Satellite Strength Indicator Bars show the strength of the signal beingreceived, and the status of the signal. The bars are either shaded or filled. Ahollow gray bar means the unit is in the process of storing orbital data it isreceiving from the satellite signal. When the bar turns solid green, the unitis using the satellite signal for navigation. A “D” in or above the bar meansdifferential corrections (WAAS or DGPS) are being applied to that satellite.Date, Time, and Current LocationThe unit gets date and time information from the satellite’s on-board atomicclock. When the unit has achieved a 2D or 3D GPS location, the current locationis shown in the location format you have selected.What is WAAS/EGNOS?The Wide Area Augmentation System (WAAS) is an FAA-funded service toimprove the overall integrity of the GPS signal for users in North America. InEurope, WAAS is referred to as EGNOS.The system is made up of satellites and approximately 25 ground referencestations positioned across the United States that monitor GPS satellite data. Twomaster stations, located on either coast, collect data from the reference stationsand create a GPS data correction message.According to the FAA’s Web site, testing of WAAS in September 2002 confirmedan accuracy performance of 1–2 meters horizontal and 2–3 meters verticalthroughout the majority of the continental United States and portions of Alaska.WAAS is just one service provider that adheres to the Minimum OperationalPerformance Standard (MOPS) for global Satellite Based Augmentation Systems(SBAS). Eventually there will be several services of worldwide geostationarycommunication satellites that broadcast integrity information and differentialcorrection data as transmitted by ground reference stations.All SBAS systems use the same receiver frequency; therefore any operationalSBAS system should be capable of providing your GPS unit with increasedaccuracy at any location in the world.Currently, enabling WAAS on your GPSMAP 3005C in regions that are notsupported by ground stations might not improve accuracy, even when receivingsignals from an SBAS satellite. In fact, it can degrade the accuracy to less thanthat provided by GPS satellites alone. For this reason, when you enable WAASon your Garmin GPS receiver, the receiver automatically uses the method thatachieves the best accuracy.For more information, go to http://gps.faa.gov.appendIX