GPS systems

Doug Yanega dyanega at DENR1.IGIS.UIUC.EDU
Wed Aug 7 11:29:34 CDT 1996

Jerry Bricker asked:

>I plan on purchasing a GPS system in the next month or so.  Can anyone
>out there suggest a system that they've had good results with?  Any
>suggestions on what features I should look for?

There is a GPS newsgroup on Usenet, sci.geo.satellite-nav, where all your
questions can be answered - when I was looking into GPS units, I spent
quite some time there, and got all sorts of useful info. The take-home
message I got was this: the kind of unit you'll want to get *does* vary
with what you intend to use it for, as each type has its limitations. For
field biology, where one is usually trying to get lat/long coordinates for
maps and locality labels, most any of the available models is suitable -
folks "in the know" seem to like the Garmin units for a number of reasons,
including durability and ease of data storage and downloading. Be warned,
however, that unless you really want to sink megabucks into the project,
you'll have to deal with two problems: (1) even if you get a unit that cuts
through the incessant signal scrambling (courtesy of the US Govt.), you
will *still* typically get more accurate altitude data from an altimeter
than you will from *any* GPS unit...I think the most accurate readings any
of the manufacturers claimed (and who knows how true the claims were) was
+/- 150 meters, and most were worse. (2) there are lots of combinations of
times and places where you will *not* be able to get a "fix" due to the
positions of the satellites relative to your own. While I was in Mexico
once using a GPS, we couldn't get any readings between 11 AM and 1 PM, for
example, over the three weeks we were in the field.
        In other words, it still helps to get good topo maps and an
altimeter, no matter what the electronic age promises...    ;-)

Doug Yanega       Illinois Natural History Survey, 607 E. Peabody Dr.
Champaign, IL 61820 USA      phone (217) 244-6817, fax (217) 333-4949
 affiliate, Univ. of Illinois Urbana-Champaign, Dept. of Entomology

  "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82

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