Re: Deternining when GPS data is good

On Wed, 20 Jun 2007 20:20:42 -0500, Ted <nospam@xxxxxx> wrote:

pwelten@xxxxxxxxx wrote:

You could have a look at the DOP (dilution of precision) values in the
NMEA strings. This is an estimate of the inaccuracy of the position.

Peter


HDOP is very poorly correlated to the actual error. I've taken 100's of
thousands of data points, and done a regression and r**2 of the error in
position vs. HDOP, and the correlation is not very good.

Me too!

In surveying a fixed position with a non-DGPS receiver over 24 hours,
I've tried to do a weighted average with DOP values, and the result is
always /worse/ than a straight arithmetic mean. Go figure!


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