Re: Sony GPS tracker for photographers With GPS if you block sats in one direction then you bias your position
according to the PR errors of the other satellites. With a handheld GPS
you can, with 7 - 9 sats, well distributed in the sky, get accuracies
well under 10 meters. If you're receiving WAAS corrections, then well
under 5 meters (even with a couple satellites blocked) is achievable in
the 48 US states. PRN 35 (WAAS) is being moved west, so some receivers
won't use the corrections (use flag is set to don't-use). I don't know
if Sony's product (above) is a WAAS receiver.
Also, if you're under heavy folliage, you might not get a valid position
at all. I used a Novatel survey GPS pack a few years ago in the woods
and had a reference receiver at my house. Both recorded the raw GPS
data simultaneously. While in the woods it wasn't clear to me that I
was getting good positions. Post processed on the computer, I got very
steady tracks. Per that software the track error was less than 1 meter
(relative to the base station) over 99% of the time.
The notion of Sony's products is not to provide highly accurate
positions but something you can refer to on a map (paper or electronic)
later on.
--
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-- e-meil: Remove FreeLunch.
Alan Browne
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