[Tagging] building:min_level, building:max_level, min_level, max_level

Martin Koppenhoefer dieterdreist at gmail.com
Mon Oct 8 16:24:47 UTC 2018

Am Mo., 8. Okt. 2018 um 17:39 Uhr schrieb Tobias Knerr <osm at tobias-knerr.de

> These aren't intended as competing tags, but as complimentary tags. A
> perfectly mapped building (indoor mapping + outdoor 3D modelling) should
> currently use both sets of tags. The tags mentioned in A are used for
> describing the outer shape of the building, whereas the tags from B are
> used for indoor mapping.

> These different use cases result in somewhat different conventions for
> the tags:
> - A is only counting above-ground levels (because only those can be
> verified without entering the building), whereas B includes underground
> levels.

A is not counting only above ground levels.
It is counting these in building:levels, but it has
"building:levels:underground" for underground levels and has also roof
levels separate.
The building:min_level definition says it is "For describing number of
values, "filling" space between ground level and bottom level of building
or part of building". min_level=-1 is a common value for the tag according
to taginfo, and it doesn't seem to contradict the definition (if a
"negative fill" is accepted).

> - B allows for things like "skipped levels", to reflect naming
> conventions chosen by the building owners, whereas A is strictly about
> counting levels, and does not take local customs for naming levels into
> account at all.

I agree that both is useful, local naming/ref and the physical situation.
>From what I understand, we do not need building:max_level for scheme A
(because the number of building levels is already clear from the 3
building:levels tags).

I was using ranges and lists in the level tag so far, something that seems
to be common as well: https://taginfo.openstreetmap.org/keys/level#values

I can see the min_level and max_level and non_existent_levels tags are
useful for describing Indoor stuff (POIs, also building parts), but it is
basically a two/three-tag-alternative to "level" with a range or list
value. Minor nitpick: rather than "non_existent_levels" the name
"skipped_levels" would have been nice, as it would also refer to generally
existing levels (in the building) which are skipped in the specific

A disadvantage from max_level and min_level and non_existent_levels is that
you cannot infer the amount of total levels (if the definition is levels as
locally used/signed), because you can never know how many levels there are
in between level 1 and level 2 (in actual buildings). It could well be
there are levels 1.1, 1.2, 1.3 or SU and SO. or foobar. We should
definitely agree on to what the max_level and min_level tags refer (if they
are written in local level names/refs, what would make sense, I agree).

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