[Tagging] Accuracy of survey

Martin Koppenhoefer dieterdreist at gmail.com
Wed Dec 31 01:08:14 UTC 2014

2014-12-24 0:21 GMT+01:00 Friedrich Volkmann <bsd at volki.at>:

> I used estimated_accuracy=* or gps_accuracy=* a couple of times, but I
> doubt
> that it prevents other mappers from moving or even deleting them. Some use
> editors like Potlatch, so they are not aware of tags. Some do thousands of
> edits, all of which are validator based "corrections". They do not ask nor
> think nor look at tags, except at those reported by the validator.

the effects of those "semi-mass-edits" or other careless following edits
must not be feared too much: as long as the original tag is preserved
(otherwise it will unlikely be noticed unless it is searched for) other
mappers might take a look and see from the history to which coordinates the
note belongs. I think notes are a good way of passing particular
information about the survey conditions to other mappers.

Positional accuracy should not be overestimated, in dense areas it is more
important to have good relative positioning (things should relate in the
map like they do in the real world, e.g. with regard to "left or right side
of the road", crossing in the same point or 2 adjacent crossings, angles,
line of sight, size relations, parallel vs. not, etc. In these settings you
typically won't find a GPS of much use when mapping today in a well mapped
urban area. In lower density areas (e.g. countryside, mountain areas) it
usually doesn't matter to have cm-precision, 10-15m are more than
sufficient, bare some potentially very rare counter examples.

Still I can understand that when you use equipment with significant higher
or lower precision than average you'd want to have a dedicated tag to
formalize entering the presumed precision in a machine readable way. just
do it ;-)

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