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 visible. -- Friedrich K. Volkmann http://www.volki.at/ Adr.: Davidgasse 76-80/14/10, 1100 Wien, Austria _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
