[OSM-talk] Defective GPS trace

[Anthony]

On Fri, Jan 1, 2010 at 6:49 PM, John Smith <deltafoxtrot256 at gmail.com>wrote:

> 2010/1/2 Aun Johnsen <lists at gimnechiske.org>:
> > Even if you have access to good arial photography, remember that it might
> be
> > out of alignment, it can be a good advise to gather some good fixes to
> check
> > the alignment of your photos, this can be several GPS tracks along your
> > trail.
>
> I'm pretty sure the imagery he's refering to is nearmap.com, which I'm
> not sure how they manage it exactly but they seem to be about
> sub-metre accuracy...
>

Where are you getting that "sub-metre accuracy" claim from?  This thread (
http://www.mail-archive.com/talk-au@openstreetmap.org/msg03414.html), which
you contributed to, throws out "3-5 meters", "1-4 meters", and "5 meters or
so".

This seems like somewhere that the wisdom of crowds actually applies.  I
think I'd trust the average of a bunch of independent GPS traces to a single
orthorectified aerial - especially in an area which isn't extremely flat.
But I guess I might be convinced otherwise, if I'm actually shown the
"sub-metre accuracy" claim, which presumably outlines the methods utilized
to ensure such accuracy.
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