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Your MYSTIC GPS receiver has been upgraded to include the latest WAAS
(Wide Area Augmentation System) technology. With WAAS your GPS receiver
can compute position locations with an accuracy never before possible in a
commercial receiver.
What is WAAS?
WAAS is a means of improving the accuracy of GPS beyond the standard civilian
signal. WAAS was developed by the FAA to provide the accuracy needed for
aircraft to perform approaches for landings. WAAS improves the accuracy of GPS
by calculating the errors in the GPS signal at several monitoring stations around
the country and then transmitting the error corrections to special WAAS satellites.
In turn, these satellites broadcast the error corrections to WAAS-capable GPS
receivers around the world.
WAAS is a free service and, with the small exception of two additional satellites
displayed on the Satellite Status screen, it will be transparent to you. There is
nothing you need do, it’s all ready to go.
How accurate will my
MYSTIC be with WAAS?
The FAA reports that expected accuracy can be improved to around 7 meters
vertically and horizontally. You can probably expect to see this level of accuracy
for 95% of the time that you are receiving WAAS signals.
What are some of the problems with WAAS?
The signal coverage with WAAS is not global like GPS satellites. In some
locations, receiving WAAS signals can be difficult and intermittent. There are two
satellites transmitting WAAS for corrections in the Americas and two more over
Africa and India providing similar coverage for Europe. These satellites are
geostationary, i.e., they stay in the same spot over the Earth equator. The two
satellites for the Americas are over the Pacific and Atlantic Oceans. Chances are
then, they will probably be near the horizon from where you are using your
MYSTIC. This increases the chance that buildings, foliage, terrain and other
obstacles could block the WAAS signal.
Also WAAS is a relatively new system and is still in its developmental stage. So on
occasion you may experience service outages. Even during these outages, your
GPS receiver will still be working, computing position fixes and helping you get to
where you want to go using the GPS signals. The only difference is you will not be
getting the precision that WAAS was providing. You can expect to see these
outages diminish as the system matures and stabilizes.
For more information on WAAS, you can visit the FAA website’s section on their
WAAS system: http://gps.faa.gov/programs/WAAS/waas.htm
WAAS
Mystic OM.book Page 122 Wednesday, October 22, 2003 8:59 PM