Martin Spott wrote:
> Does anyone have experiences with portable GPS recievers ? Do they
> tend to increase the precision of their coordinate output if you
> remain at a location for several minutes ?

My wife have gotten into geocachine (www.geocaching.com) over the last
two years, so we've played with these things quite a bit.

Yes, almost all consumer devices will do averaging, although none of
them tell you the algorithm they use.  Given enough time, they will
converge down to a value that is accurate to within the accuracy of
the system (a few meters).

I doubt a few minutes would be enough, I would give it several hours
to ensure that a large number of satellites triplets get used in the
solution.  Averaging over a few minutes is only going to reduce
sampling error, it probably won't be switching between its satellite
signals, so systematic error of one satellites signal (due to
ionosphere refraction, etc...) won't be caught.

Honestly, there's a lot of voodoo in consumer GPS hardware.  Sometimes
the sky looks great, you see really strong signal from 8 satellites,
and still get a fix that is off by 40m or more and need to reboot the
unit to get it to see straight.

Andy

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