building:min_level, building:max_level, min_level, max_level

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building:min_level, building:max_level, min_level, max_level

dieterdreist
I just noticed once again both tags are around:

A)
building:min_level
building:max_level (is used but AFAIK not documented)

and B)
min_level
max_level

Version A is used and defined here:

Version B mentions the tags for buildings, but doesn't specify the details:

Do we really need 2 ocmpeting tags for this? If yes, we should add the prefixed variant to the building page as well. Usage numbers are low,"mixed" and not clearly in one direction or the other.

Cheers,
Martin

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Re: building:min_level, building:max_level, min_level, max_level

Tordanik
On 08.10.2018 15:55, Martin Koppenhoefer wrote:
> Version A is used and defined here:
> https://wiki.openstreetmap.org/wiki/Key:building:levels
> https://wiki.openstreetmap.org/wiki/Key:building:min_level
> https://wiki.openstreetmap.org/wiki/Simple_3D_buildings
>
> Version B mentions the tags for buildings, but doesn't specify the details:
> https://wiki.openstreetmap.org/wiki/Simple_Indoor_Tagging
>
> Do we really need 2 ocmpeting tags for this?

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.
- 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.

The goal of mapping both is to match up the outdoor and indoor
rendering. Or putting it differently, it answers the question which
floor should be visible behind which row of windows.

Of course, we can imagine alternative approaches for achieving this. For
example, there could be some kind of tag that explicitly expresses
"outdoor-level 0 corresponds to indoor-level -1". If we find a solution
for the problem that's easier to understand and use that the currently
documented one, it may be worth considering. But the S3DB building:*=*
tags on their own are not a suitable replacement for Simple Indoor
Tagging's min/max levels.

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Re: building:min_level, building:max_level, min_level, max_level

dieterdreist
Am Mo., 8. Okt. 2018 um 17:39 Uhr schrieb Tobias Knerr <[hidden email]>:
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 building:part.

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).

Cheers,
Martin


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