[Tagging] Tunnels and bridges

[Martin Vonwald]

In my opinion this is a rather obvious approach therefore I'm not
surprised that someone already came up with it earlier. But I am
definitively surprised that we don't have any documentation in the
wiki for it. I see a lot of bridges with many ways running over it
(two footways, two cycleways, two carriageways) and on the map it just
looks AWFUL! But the renderer can not display it any better because it
doesn't have the appropriate information.

So I would suggest that we decide which tag would be good for the
bridge, document it and start tagging it this way to get things going
;-)

Let's first concentrate on bridges. In my opinion we need the following tags:
* bridge=<type> : use this tag just like it is used at the moment. If
the value would be "yes" it should be optional.
* layer=<x> : this should get the same layer as the ways running over
it. One could argue that this should get a layer below the ways, but I
find this rather counter-intuitive. See comment below!
* <something>=bridge : this is the tag we should decide one. I guess
the value "bridge" is unchallenged.

So for a simple bridge we would end up with one way describing the
outline and 2-3 tags.

Concerning the layer-tag we have to consider something more: how about
bridges with more than one level, e.g. on top are the roads and below
them the subway and some cycleways. There is already a concept that
supports this: building-parts. It might be a good idea to integrate
bridges in this concept. I am definitively not familiar with that
concept but if I am not mistaken one can specify different levels of a
building. So if we would use that concept we could specify a bridge
with two levels with the tags level=1 + layer=<x> for the lower part
and level=2 + layer=<x+1> for the upper part. The tagging of the
"simple" case (i.e. with only one level) wouldn't change.

Any experts here for 3D tagging? Would a bridge fit into this concept?


regards,
Martin





2013/1/31 Pieren <pieren3 at gmail.com>:
> On Thu, Jan 31, 2013 at 2:06 PM, Martin Koppenhoefer
> <dieterdreist at gmail.com> wrote:
>>
>> 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.
>
> Instead of "building=bridge", you might choose "man_made=bridge_deck"
> or simply "bridge=deck" ?
>
> Btw, the idea is not new. Check this bridge I traced in march 2010:
> http://www.openstreetmap.org/browse/way/53582123/history
>
> I used the tags combination "highway=bridge" + "area=yes". Then it was
> replaced by "bridge=yes" + "area=yes" and finally by
> "building=bridge".
> I guess the "building=*" tag is used for rendering purpose. Which is
> not correct.
>
> Pieren
>
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