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Generally, the position displayed by a GPS receiver using the CIA signals should by accurate to
within 100
feet,
and for 50% of the time it shoUld be accurate to within about 40 feet. It is normal for
the displayed position to "wander" slightly over time. For the same
reason,
the altitude displayed by
a GPS receiver will also vary slightly.
II is important to understand that such
variations
are inherent in GPS and do not indicate a fault in
the
receiver.
Remember also, that GPS is operated by the DOD and is subject to military require-
ments. There is no guarantee that signals will always be available, or that any displayed poSition or
altitude will be
accurate.
THE GPS RECEIVER
A GPS receiver such as the GMR-GPS uses the CIA signals from the satellites to determine its
position on
earth.
Signals from three satellites are needed to provide an unambiguous position
fix,
with reliable attitude indications requiring a fourth. In most circumstances, a GPS receiver will be
able to receive signals from more than four satellites and can decide which it will use to give the best
position.
Signals from GPS satellites are relatively weak and are easily blocked by obstacles or local
screen·
ing.
GPS receivers may bot work well indoors, in vehicles or underneath trees or foliage. For best
results, the receiver should be able to "see" as much of the sky as
possible.
THE GMR-GPS UNIT
The Audiovox GMR-GPS provides you with the features of a precise hand-held GPS unit designed
for general purpose locating and
navigation.
Not only can it determine your actual position. it can
also guide you to a destination by establishing and storing waypoints to mark the trail or
route,
and
allow you to return to your original starting point.
But what makes this unit unique, is the incorporation of GMRS capability, whereby your position
can be transmitted to another GMR-GPS unit, thereby allowing another party to know your exact
position, your intended route, and how long it will take you to arrive at that
position.
By including three modes of operation, your GMA-GPS can act as a mobile radio transceiver only,
as a GPS unit only or as a combination of the two technologies for navigation and communication
purposes. The GMR-GPS incorporates the following features and capabilities:
•
WAYPOINTS: The unit provides 150 waypoints with user-selected names and graphic
symbols.
•
ROUTE:
Lets you navigate up to 10 routes with 20 way points in each route.
•
TRACKS: Provides an automatic track log using live saved tracks; these tracks allow
the user to locate the beginning and end point of each track.
•
MARK:
Allows the user to save and transmit his/her location to other GMR-GPS units
tuned to the same channel (up to a distance of approximately 5 miles).
•
GP LOCATOR: Allows the user to receive and store position coordinates of other
GMR-GPS users.
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