[Tagging] Simplify building:part areas

[Javier Sánchez Portero]

Hello Tobias and Cristian

2017-08-18 17:41 GMT+01:00 Tobias Knerr <osm at tobias-knerr.de>:

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

But in the other case, I end up with this:

way1: building = apartments + building:levels = 4
way2: building:part = yes + building:levels = 3
way3: building:part = yes + building:levels = 4
way1 == way2
way3 is inside way1

Josm validation will raises a warning for duplicated ways (way1 and way2).
If I use the open ways + MP relations schema mentioned by Christian, the
situation is almost the same. I will end up with three MP relations instead
of closed ways and Josm validation will raises a warning for relations with
the same members.


> 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.
>
> Tobias
>

I accept this, although is not clearly expressed in
http://wiki.openstreetmap.org/wiki/Key:building:levels
Does everyone agree that building:levels refers to the maximum number of
building levels?

Javier
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