[at-l] GPS question

[wdlists at optonline.net (Walter Daniels)]

> 
> If you are really serious about using GPS in the third world, 
> you need to move up to a professional unit from someone like 
> Trimble. The consumer oriented units by and large are not 
> going to perform adequately for your needs. They barely 
> suffice in North America.
> 
There is no need to use a professional unit over a consumer unit for general
navigation. The professional units need reference to differential correction
to do any better than consumer units. A consumer unit will reliably get you
within 30 ft of a known location and if you can't see the ultimate goal from
there you are in big trouble.

I have been out numerous times with  both a consumer and a professional
unit. We both lose signal in the same places. Admittedly I cheat with my
consumer unit and have an external antenna mounted on a pole above my head,
just like the professional units. This is necessary to prevent blocking some
satellite signals with your body.

I never go out in the field in places I am not intimately familiar with
without a map, but there is at least one scenario where a GPS would be
helpful even without one. Imagine following a triangular course where you
start at your car and go up to a ridge, walk along it for a long ways and
want to bushwhack back to your car by the shortest path. You could do this
without a map (but you may fall over a cliff if you are not careful :-).

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