Hi.
Am 18.02.2011 13:21, schrieb Tobias Knerr:
On 18.02.2011 12:04, Peter Wendorff wrote:
Am 18.02.2011 11:16, schrieb M∡rtin Koppenhoefer:
building_levels should be the amount of building
levels. If a building forms a "bridge" like in the illustration, where
adjacent buildings have 7 levels, the "bridge" has only 2 levels and
the 5 levels below are void, the proposal states you should still
apply building_levels=7 and count the voids as levels.
[...]
My purpose with this design of the tagging scheme was something often
applied in OSM: backwards compatibility.
Most people tagging level counts of buildings I think would not think as you describe for
"bridges".
As bridges do not appear alone and instead are always part of a building
including the sides of the bridge, the building as a whole would have been
tagged with building_levels=7.
The need to apply backwards compatibility to this issue at all arises
from another design decision that I'm not convinced of:
That building parts are tagged as buildings.
In my opinion, the better choice would be to invent a new tag for
building parts, and map the entire building's outline as building=yes in
addition to the individual parts.
+0.5
Yes, it could be a good idea to invent a separate tag for building parts.
I would appreciate that (and initially these issues are part of the
reason why my proposal is not a proposed tagging scheme in the common
sense of the proposal process).
But one question is left here:
What is the building outline you would like to map in future as
building=yes, too?
Is it (a) the "maximum size outline" as shown in aerial imagery?
Is it (b) the "on-ground-outline" a pedestrian would be able to go along?
Is it (c) the "maximum size outline" including underground parts not
build up above ground - like bigger underground parking areas?
Is (d) the building=yes a fallback for renderers not supporting the
building_parts?
Each of these possibilities has it's advantages:
A blind pedestrian would benefit from (b) as that's the "barrier"
outline and the leading lines he can percept with his cane.
A airplane pilot woult benefit from (c) as it corresponds to what he can
see.
A mapper using aerial images as a source would have the easiest job with
interpretation (c) as that's exactly (given that the aerial is exact)
what he can see at the images.
This would provide an obvious place to
tag information related to the entire building, independently from
similar information related only to a building part. Information in this
case can be the number of levels, but also things like names (it's not
entirely uncommon for building parts to have names of their own that are
not the same as the name of the entire building).
Yes, there are additional arguments to change something here.
Feel free to do so - that's the reason why it's not yet a "real proposal".
regards
Peter
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