[Tagging] Tunnels and bridges

[Martin Koppenhoefer]

2013/1/31 Tobias Knerr <osm at tobias-knerr.de>:
> On 31.01.2013 13:24, Janko Mihelić wrote:
>> I like building=bridge.
>
> Not a good choice imo. According to a recent discussion, mappers might
> want to use that tag specifically to map buildings built into bridges -
> like these:
>
> http://ampelmann-restaurant.de/content/images/1a162245ce191485484b155c6eae79b9.jpg


I wouldn't call this a "bridge", it is a vault, but the "bridge" (or
viaduct) if you wanted to map it would (IMHO) be the structure as a
whole, not just a single segment.


> Bridges also have to be handled completely differently in code than
> normal buildings for any remotely sophisticated rendering. So even if
> you want to avoid bridge relations (which I don't necessarily agree
> with, see my other mail), please choose a new, unambiguous key for the
> bridge outlines.


Yes, probably you would want to add a special treatment in rendering
for bridges, but it wouldn't be necessary missleading or confusing to
have them rendered the same way than a ordinary building. If there was
a key "building=bridge" with a common usecase I won't see any
ambiguity.

There are bridge buildings, which don't carry roads or rails, like these:
http://www.spiegel.de/pics/92/0,1020,1536992,00.jpg
http://www.gropar.ch/typo3temp/pics/41b05acade.jpg
http://www.schoendorfer.de/neu/baustellen/zollamt_walserberg/bilder/01.jpg

and every building built on stuilts might structurally be a bridge but
I still don't see the problem, you would distinct these by looking
whether there is a road going over them on the same layer (ok, there
might be a bridge-like building with a road on top of it, in this case
you'd probably need the relation, but the relation would be useful
anyway, this is not necessarily an alternative to relations in all
situations, but could make them unneccesary in many cases)).

cheers,
Martin