[Tagging] Accuracy of survey
bsd at volki.at
Tue Dec 23 22:59:58 UTC 2014
On 23.12.2014 17:57, Tom Pfeifer wrote:
> I would consider that a non-issue as you said, for those reasons:
> - When it comes to GPS traces on objects that don't move (*), the
> beauty of crowdsourcing is on our side. The collection of
> traces over a longer time creates a cloud of traces which
> form a Gaussian bell curve, in density, over the ground truth.
> Thus a junction of two road traced again and again is still
> a good reference point to calibrate aerial imagery.
There are no GPS traces for pipeline markes. There are traces for roads and
paths only. These traces can bear a systematic error due to reflections
(e.g. under a cliff).
Even if you collect plenty of GPS traces with no systematic error, these
still cannot beat a theodolite triangulation.
> - We are getting access to increasingly better geo-referenced
> aerial imagery, thus mapping can now use different sources
> and calibrate between them.
In places where GPS is most inaccurate, e.g. in a gorge covered by woods,
aerial images are inaccurate too, and most of the ground details are not
Friedrich K. Volkmann http://www.volki.at/
Adr.: Davidgasse 76-80/14/10, 1100 Wien, Austria
More information about the Tagging