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iQue 3600a Que Applications Guide 89
What is WAAS?
The Wide Area Augmentation System (WAAS) is an
FAA-funded project to improve the overall integrity
of the GPS signal and increase position accuracy for
users in North America.
The system is made up of satellites and approximately
twenty-five 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 in September
2002 of WAAS 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 and
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 Garmin iQue
3600a 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. To enable WAAS, refer to page 75.
For more information, go to http://gps.faa.gov/
Programs/WAAS/waas.htm.
APPENDIX > LEARNING ABOUT GPS