[OSM-dev] Garmin GPX madness

[Gora Mohanty]

On Mon, 22 Sep 2008 11:36:30 +0100
"Nick Black" <nickblack1 at gmail.com> wrote:

> If you had 30 traces down a road and no dop information and you
> derived a centre line, using only the lat lons of the 30 different
> traces, how much less precise would the result be than taking 30
> traces with dop info and figuring out a centre line?
[...]

Um, that would depend on the dop info, i.e., does it
make some tracks significantly more precise than the
others? It is impossible to make a general prediction.

In general, given a 1D value x, measured with RMS
error, s, from n independent, non-correlated observations;
the effect of averaging all n values is that the RMS
error of the mean value, <x>, is s/sqrt(n), i.e., the
precision to which the 1D position is measured improves
as the square root of the number of measurements.

Regards,
Gora