When you hear that your GPS is
accurate to 15 meters, just what does that mean to you in the backcountry?
Today, a GPS receiver is accurate to
the design specifications of the model. Generally, a GPS is accurate to plus or
minus 15 meters (a circle with a15 meter radius or 30 meters in diameter.) Many
models offer more accuracy through the technology of the Wide Area Augmentation
System (WAAS); 3 meters is possible. (Note that to take advantage of WAAS that
option must be "enabled" in the setup function of the main menu.)
- Number of satellites signals being received
- Multi-path interference (signals reflected
off a surface yet being received)
- The age of the unit and antenna model/type
- Receiver sensitivity
- Atmospherics (such as solar flares and sun
spot activity)
To counter the factors
listed above the wilderness traveler has only a few options and these include:
- Buying a new unit
- Relocate to an area with a clear sky view
(get away from trees)
- Give the receiver more time to capture and
process the satellite signal
Giving a receiver the
time to capture and process data received is especially true with the older
models. For example, I have students attending my classes bringing in the older
Garmin 12, Garmin Etrek Summit, Magellan 315 and Magellan Sport Track. These
are old but functional, usable and models that will definitely get one back to
the truck or trail head. My recommendation is to give the receiver the time to
do the job; this could be five minutes. (If it takes longer than 5 minutes you
may have a problem with the receiver.) Remember, with the older models, if your
travel over 50 miles from the location where the unit was last used, it will
take more than 5 minutes to "re-initialize;" check the owner's
manual.
In the example above, the hiker will
be somewhere in the lane traveling from "start" to "elk
camp." At one moment in time the hiker may very well be in the center of
the lane but a short time later his actual position will shift ahead, to the
side and so on.
Don't rush navigation. Navigation
deserves the time, patience and attention to detail as does any other skill of
the backcountry.
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