GPSMAP 3205 Owner’s Manual
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PPENDIX
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S
ATELLITE
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NFORMATION
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WAAS/EGNOS?
Satellite Information
Satellite Sky View
45°
90°
Outer ring -
the horizon
Inner ring- 45°
above the horizon
Center dot - 90°
above the horizon
Satellite Location
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 be set to display satellite location
with North or your current track at the top of the display.
Satellite Strength Indicator Bars
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. The
hollow gray bar means the GPS is in the process of storing orbital data it is
receiving from the satellite signal. When the bar turns solid green, the GPS
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.
Date, Time, and Current Location
The GPS gets date and time information from the satellite’s on-board atomic
clock. When the GPS receiver has achieved a 2D or 3D GPS location, the current
location is shown in the selected location format.
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 3205 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
.
Summary of Contents for GPSMAP 3205 - Marine GPS Receiver
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