[NatureNS] GPS deal - spatial resolution

Date: Mon, 19 Oct 2009 23:31:04 -0300
From: Stephen Shaw <srshaw@DAL.CA>
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Hi Fritz or others,
Thanks -- it sounds like a good deal.

What's the best GPS spatial resolution you can get in the field these 
days, for
close-scale local mapping?  My recollection is that a few years ago it was
quoted as no better than about 15 feet, even with several satellites optimally
in view, which is a bit coarse for an application I was thinking of.  Is it
still in the same ballpark or has it improved?

If you were to stand in one place and do repeated determinations and then
average these numbers, would you get closer to determining more accurate
spatial coordinates for that spot?  You might expect this if the source of
spatial uncertainty were `random` internal noise in the receiver, or something
similar. Or does the source of uncertainty in the GPS reading lie 
elsewhere?  I
think I asked this once before a few years ago but don't remember getting a
clear reply, and never bought a unit.  There was even a story that the spatial
resolution is intrinsically much finer than is available to the public, but
that the US military has deliberately detuned the public output so it was less
precise, presumably so it could not be used for accurate nefarious targetting
-- I'm guessing that this was an urban legend?

Steve
(Halifax)


Quoting Fritz McEvoy <fritzmcevoy@hotmail.com>:
> Hi All,
>    I received a flyer email from "The Source" with a great deal on a 
> Garmin Etrax Legend GPS- $60.00!!! (regular $180.00). This is a small 
> dependable GPS I have used for years.  I don't know why it is selling 
> so cheaply but for those looking for a good backup or starter GPS 
> this seems to be a good deal. If anyone knows why they are selling so 
> cheaply let us know.
>
> You will need to get the Garmin Maps to get the best use out of the GPS.
> All the best.
>
>                  Fritz McEvoy
>                    Sunrise Valley CB




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