[Tagging] Feature Proposal - RFC - survey_point:benchmark

Greg Troxel gdt at lexort.com
Tue Mar 10 22:45:05 UTC 2020

Anne-Karoline Distel <annekadistel at web.de> writes:

> I've been surveying benchmarks for the past four months and I would like

I'm glad to hear that.

> to propose an alternative to benchmark=yes for survey points:
> https://wiki.openstreetmap.org/wiki/Proposed_features/survey_point:benchmark
> The reason being that I would like to also propose
> survey_point:hexagonal_bolt and survey_point:ground_bolt with it.

I think this is blurring two separate concepts: a particular logical
purpose of passive survey control mark, and the form of such a mark.

In the US, we use "benchmark" to refer to a passive mark for elevation,
essentially always by leveling.  We use "triangulation station" for
passive marks for horizontal controls, and I'm not sure but perhaps
ellipsoidal station for those which use GNSS to establish 3d coordinates
relative to the ellipsoid of a datum.

For all of these, the big point is that there's some reference that can
be recovered, and the exact physical form is not that important.

While the above words are guided by my understanding of US practice, the
historical separation of horizontal and vertical control networks and
the move to GNSS and ellipsoidal positions is I think pretty universal.

So I would suggest that there be tags for type/purpose, keeping in mind
that some physical marks were both horizontal and vertical controls.

It makes senes to have further tags for the physical type of mark.
> Definition: Ordnance survey point usually chiselled in stone with its
> typical horizontal bar and arrow below on vertical surfaces, dot with
> arrow below on horizontal surfaces. Now often replaced by hexagonal
> bolts in walls or bolts in the ground.

That sounds very UK specific.   In OSM I think we need to have
descriptions that people everywhere can interpret and make sense of.

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