A sense of where you are at

Gary R Noonan carabid at CSD4.CSD.UWM.EDU
Fri Nov 6 09:57:07 CST 1992

It's good to see that competition is driving prices down.  Another good unit
to check si the Garmin GPS 50.  I used such a unit for 84 days last summer
in the western United States and was very pleased.  In most places it found
4 satellites and was able to give latitude, longitude and elevation.  In
a few (about three) places in the far west it was able to find only 3
satellites and could not give elevation data.
	One thing to remember all GPS systems is that the federal government
deliberately degrades the accuracy of the satellite data.  I found that
the Garmin gave elevations that varied at a site by as much as 80 to 100 meters
and this was apparently due to the federal degrading.  The unit would if left
on long enough cycle through a range of elevations at some places and times.
At other times and places it cycled through only a very small range or picked
a single elevation and stayed with it.  A thing to note is that the accuracy
quoted for all GPS systems consists of a set of ideal figures and usually is
for the most expensive GPS systems.  To get the highest accuracy one needs
two very expensive GPS systems, with one of them set on a know location.
	I found the Garmin quite good.  It changed its lat and lon readings
when we moved from one part of a site to another and certainly had enough
accuracy for my work.  I did however always check elevations against an
expensive altimeter ($500 bucks paid for it about 15 years ago) and in a few
instances used the altimeter to pick an elevation within the range of
elevations given by the Garmin--again the darn federal degrading of signals!
	The Garmin GPS 50 is actually made primarily for marine use and had
a lot of features for navigation.  However, it was easy to use, simply
turn it on and it obtained the latitude, longitude, elevation.
	To get the price of $825 which I paid, I had to order direct from the
factory and certify that the Milwaukee Public Museum is a non profit
educational institution.
	Garmin International, Inc.
	11206 Thompson Avenue
	Lenexa, KS 66219
	1-800, 800-1020

	I purchased the unit last April; competition might have driven
prices down by now.

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