[Tagging] Simplify building:part areas

Tobias Knerr osm at tobias-knerr.de
Fri Aug 18 16:41:12 UTC 2017

On 18.08.2017 10:01, Tom Pfeifer wrote:
> If e.g. the lower floors of the apartment building is wider than the
> upper floors, you can tag the outline with both, building=apartments and
> building:part=yes and the appropriate 3D-properties, and the narrower
> upper floors with building:part=yes and 3D-properties, but without
> building=*.

It's not a good idea to use building and building:part tags on the same
way. Doing so typically gives incorrect information to data consumers,
because the number of levels for the building as a whole is not the same
as the number of levels for the building part.

In your example, the building part for the lower levels would be tagged:

+ building:part = yes
+ building:levels = <number of lower levels>

And as you said, one important function of the building outline is
backwards compatibility for non-3D-applications. Such an application
will conclude that this building has <number of lower levels> levels,
which is not the case.


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