[Tagging] Survey points

moltonel 3x Combo moltonel at gmail.com
Wed Mar 11 09:46:02 UTC 2015

On 11/03/2015, Malcolm Herring <malcolm.herring at btinternet.com> wrote:
> OK, the mapper in question did not reply, but silently removed the tags.
> This leaves me none the wiser as to the more widespread usage of this tag.

At least that's reassurance that a buoy, which can drift quite a bit
on the surface, isn't considered as a survey point :p

> Looking closer at the data, it appears that "man_made=survey_point" is
> very often added to prominent objects, particularly towers, masts and
> lighthouses. Could it be that some survey agencies use these objects as
> triangulation points?

Often yes. And to make that survey point "official" when it isn't a
purpose-built structure, there is often a reference plaque placed on
the structure at the exact location of the point.

> If so, it raises a couple of issues:
> 1. The "man_made" key should refer to the structure, not its usage.
> 2. The drift towards micro-mapping means that such objects, originally
> mapped as nodes, get converted to plan outlines and the tags moved to
> that closed way. If the intent of the "survey_point" mapper was to set a
> lat/lon positional reference, then that scheme is undone.
> Might it not be appropriate to add a note in the Wiki page for this tag
> that it should not be added it to existing objects, but to always create
> a separate node?

The wiki already mentions that the tag only applies to nodes, which
should in theory catch "upgraded to an area" mishapps. There are
currently 64 survey_point ways in the db (compared to 287000 nodes),
so the problem exists but isn't too big. Care to review them ?

That said, a "always add survey points as their own node"
recommendation on the wiki can't hurt.

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