[Tagging] Additional sub tags for survey mark

[Andrew Harvey]

Being able to distinguish different types of survey marks and points is
very much needed in OSM, it would be great to see this formalised on the
wiki.

I like the idea of modelling it after https://wiki.openstreetmap.org/wiki/
Seamarks/Categories_of_Objects#Control_Points_.28CATCTR.29 as that seems
well thought out.

I like the idea of using configuration as a sub key to survey_point, rather
than the undocumented by suggested tags of "triangulation_point=yes and
benchmark=yes".

My only question is the wiki page currently says "Since multiple survey
points are possible on one object (eg. a benchmark on a triangulation
point/pillar) then in order to avoid multiple values within one key, such
as a semicolon-delimited list in survey_point=*, it may be advisable to use
something like triangulation_point=yes and benchmark=yes to allow clean
coexistence of tags on one node.".

How would your proposal work with multiple survey points on the one object?
I've never come across this so not sure myself.

I think observation is a valid configuration, as I've seen observatories
used as the datum on old maps.

On 21 November 2017 at 10:47, Warin <61sundowner at gmail.com> wrote:

> Hi,
>
> There have been attempts in the past to add sub tags to
> man_made=survey_point https://wiki.openstreetmap.org
> /wiki/Tag:man_made%3Dsurvey_point
>
> To me there are 2 'types'. they are quite different;
>
> Triangulation (or 'trig point') that are visible over quite some distance
> (say over 2 km),
> used to triangulate a position without having to go to the mark. Usually a
> pole standing on top of a rise/hill.
>
> Benchmarks that are visible on the surface but cannot be sighted at any
> distance. They can be small brass plaques fastened to the ground or
> engraved into stone.
> These are used by surveyors by placing a tripod over the mark, thus have
> to be locally approached.
>
> If consideration is given to https://wiki.openstreetmap.org
> /wiki/Seamarks/Categories_of_Objects#Control_Points_.28CATCTR.29
>
> then expanding survey_point in a similar manner could be
>
> survey_point:configuration=triangulation/benchmark
>
> I use 'configuration' rather then 'type' or 'category' as it is more
> specific as to what is meant.
>
> Any thoughts?
> Are there any other configurations?
>
>
>
>
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