[Tagging] Additional sub tags for survey mark

Craig Wallace craigw84+osm at gmail.com
Thu Nov 23 14:37:53 UTC 2017


On 2017-11-20 23:47, Warin 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?
It would be useful to tag the physical style of the survey point. ie the 
size and shape and what it  is made of. Is it a pillar, or just a metal 
plate or bolt on the ground. This would tell you whether it is an 
obvious landmark or not.

Tagging what the survey point is used for is a separate thing. ie 
triangulation, or a benchmark. Nowadays most trig points are redundant, 
so they are not actually used for any sort of survey work. Though in the 
UK there are some still maintained as "passive stations", plus a few 
"active stations" (with a GPS receiver).
Note there are some "Fundamental Benchmarks", which are a small stone 
pillar.

Some of the common types in the UK: http://trigpointing.uk/wiki/Types



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