Garmin 3005c Manuale Proprietario

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 WAAS/EGNOS?

The location of each available satellite is shown over two location rings on 

the Satellite Information Page. The outer ring represents the horizon, the 

inner ring represents 45° above the horizon, and the center represents directly 

overhead. When the unit is using a satellite for navigation, the satellite number 

is highlighted on the location rings. The unit can display satellite location with 

North or your current track at the top of the display. 

The Satellite Strength Indicator Bars show the strength of the signal being 

received, and the status of the signal. The bars are either shaded or filled. A 

hollow gray bar means the unit is in the process of storing orbital data it is 

receiving from the satellite signal. When the bar turns solid green, the unit 

is using the satellite signal for navigation. A “D” in or above the bar means 

differential corrections (WAAS or DGPS) are being applied to that satellite.

The unit gets date and time information from the satellite’s on-board atomic 

clock. When the unit has achieved a 2D or 3D GPS location, the current location 

is shown in the location format you have selected.

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  Minimum Operational 

Performance Standard (MOPS) 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 3005C in regions that are not 

supported by ground stations might 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

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