[Tagging] Additional sub tags for survey mark

Warin 61sundowner at gmail.com
Wed Nov 22 22:36:37 UTC 2017

On 21-Nov-17 08:32 PM, Mark Wagner wrote:

> On Tue, 21 Nov 2017 10:47:30 +1100
> 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?
> Survey marks in the US tend to come in three types:
> 1) Benchmarks, which are typically a bronze disk solidly attached to
> the top of something.  Both the horizontal and vertical positions are
> usually well-surveyed.
> 2) Vertical control points, which are typically a bronze disk affixed
> to the side of something.  The vertical position is well-surveyed, but
> the horizontal position is only recorded well enough to let a surveyor
> find it.

I think of these as both kinds of benchmarks.

The accuracy of the horizontal and vertical location are different and could be tagged (somehow - I've not investigated this ... )

The orientation could also be tagged .. I think these are already tags for orientation within OSM for other features.

> 3) Reference marks.  Typically, a bronze disk attached to something
> that gives directions to a nearby survey mark.  The position isn't
> recorded beyond what's needed to find it, if that.

Humm .. If the survey mark itself is mapped there should be no reason to map these 'reference marks'?
It would be like mapping the sign carrying the street name.

> (There are also horizontal control points, but these tend to be things
> like flagpoles and smokestacks which have been surveyed and documented
> for use as survey marks.)

Those would form the same function as a trig point.

And could be tagged the same way?

Should have some indication of accuracy.

Any thing that is mapped in OSM could be used the same way as a true trig point,

but the accuracy would be the key thing between a hill top and a  trig point as the trig point would be determined with much higher precision.

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