[Tagging] Feature Proposal - RFC - Tag:natural=mesa and Tag:natural=butte

[Joseph Eisenberg]

On 4/26/19, Christoph Hormann <osm at imagico.de> wrote:
> As i understand it a butte is not generally assumed to be flat topped in
> common language use, the key elements here are height larger than width
> and cliffs on all sides.

That's true. The top is only relatively flat compared to the surrounding cliffs.

> For mesas i already mentioned the fairly precise criterion that the
> elevation variance along the top (or more precisely the derivation from
> flatness - some amount of tilt in geology is fairly common) needs to be
> significantly smaller than the overall height of the structure.
> Combined with a firm requirement for cliffs on all sides this would
> make a fairly precise definition.

It's difficult to think of a good way to word this. I'll try to add a
clarification that explains what is meant by "flat."

> It should also be mentioned that these tags are not meant to be a
> substitute for locally mapping the actual cliffs - which while by
> definition surrounding the whole structure can be staggered of course.

The tag natural=cliff was mentioned in the proposals and cliffs are
part of the definition, but I'll add something explicit about the
importance of mapping the cliffs.

I'll also add some visual examples that show the cliffs sharing the
same nodes as the natural=mesa way when mapped as an area.

> For natural=plateau i don't see a chance of this becoming a meaningful
> tag.  Too much inherent vagueness in the very idea.  If you'd try to
> define it more precisely it would almost certainly be advisable to use
> a different tag that is not misleading the mapper to have a much
> broader scope.

I agree that this isn't a very specific tag. I don't intend to do
anything else with the natural=plateau proposal page, but since the
tag is already in use I wanted to suggest that it only be used for
nodes, since mapping plateaus as an area isn't verifiable. Currently
some mappers are using it on areas, and it would be good to have a
wiki page that suggests tagging on nodes only. Also, it shows why the
more precise natural=mesa and natural=butte tags are needed, instead
of just using natural=plateau for all of them.