With building:part you are actually describing 3D volumes. These volumes
don't necessarily start at ground level, but ideally should not
intersect in 3D. As you can see in the Simple 3D building specification,
you can set a "building:min_level" and "min_height" to "raise" a certain
part from ground level to its appropriate starting height. So in your
case of a large single story ground level part, and a smaller top
section, you could set building:min_level and min_height tags on the
part for the smaller section to raise it above the large section/part,
which in that case should NOT be a multipolygon.
Of course, like you suggested, there is the alternative solution of
creating a multipolygon and setting the higher part to start at ground
level as well by not specifying building:min_level and min_height, and
that would be correct too in terms of non-intersecting 3D volumes, but
the first solution without multipolygon seems more logical in this case
(unless the higher part was in reality a true separate section starting
at a ground level, e.g. office, within a larger structure, in which case
it might make sense to use the MP option if you would like to tag
function on the building:part as well).
Marco
Op 18-8-2017 om 10:36 schreef Javier Sánchez Portero:
Sorry, I should have taken time to give some examples. Please read
below (I rev.
2017-08-18 1:30 GMT+01:00 Clifford Snow <cliff...@snowandsnow.us
<mailto:cliff...@snowandsnow.us>>:
On Thu, Aug 17, 2017 at 4:12 PM, Javier Sánchez Portero
<javiers...@gmail.com <mailto:javiers...@gmail.com>> wrote:
I am thinking in ways to reduce the complexity that introduces
the mapping of parts of buildings. For example:
I have reversed the order of the points
* In the wiki [1] says that the outline should be tagged with
building:levels and height, but this, if the parts cover the
whole outline, is a duplication since these tags will always
be in some of the parts. Could I delete the part(s) whose
labels match those of the outline?
If you use a multipolygon, then the multipolygon would contain the
levels and height.
I'm refering to 3D modeling of building height and levels, according
to [1]. For example, this building [2] have two heights and should be
drawn two parts inside the building footprint, one with
(building:part=yes, building:levels=1, height=3) [3], and another one
with (building:part=yes, building:levels=2, height=6). As the building
footprint [2] could have the levels and height tags I put them in it
avoiding to draw one part. I meant, the building area is not entirely
covered by building:part areas. All the building in this village was
drawn according to this.
I take the rule to put in the building:levels and height tags of the
full building those of the level wich parts sum a greatest area
instead of the maximum values. For a example see the adjacent building
to the left [4]. It have (building:levels=1, height=3) instead of the
maximum values (building:levels=2, height=6) of the building:part [5].
This way I avoid to draw two parts inside the building. I consider
that the maximum building:levels and height could be calculated by a
consumer from the building and its parts instead. I'm wrong with it?
But it's against what says the wiki [6].
* If one part is inscribed within a larger one, can I use
simple ways overlapped and leave to the render decide how to
draw them or should I create a multipolygon for the larger
part with the smaller part with inner role? I'm prone to the
first.
An example would help. If the building has an inner court yard,
then a multipolygon would be appropriate, with the inner court
yard with an inner role.
I'm not referring to buildings with holes but to nested building:part
areas. Consider this building [7] with a big one-story part and a
smaller two-story part [8] within it. If I use the full detailled
schema I will need a multipolygon relation for the one-story part, but
I avoid this putting the tags in the footprint (violating the rule of
maximum levels and height in it). I don't have real example at hand,
but supposes another three-story part inscribed inside the two-story
part [8]. should I use a multipolygon for the two-story part to fully
separate it area from the three-story part area? Or could I just draw
the inner three-story part, overlapping both areas?
[1] https://wiki.openstreetmap.org/wiki/Simple_3D_buildings
[2] http://www.openstreetmap.org/way/459549932
[3] http://www.openstreetmap.org/way/459550128
[4] http://www.openstreetmap.org/way/459549958
[5] http://www.openstreetmap.org/way/459550129
[6] https://wiki.openstreetmap.org/wiki/Key:building:part
[7] http://www.openstreetmap.org/way/215569626
[8] http://www.openstreetmap.org/way/459573978
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