[OSM-talk] viaduct?

[Andy Robinson]

On 02/11/2007, Thomas Wood <grand.edgemaster at gmail.com> wrote:
>
> On 11/2/07, Florian Schmitt <ml-osm-talk at florian-schmitt.net> wrote:
> > Hi,
> >
> > i'm not sure about the use of the viaduct tag. The wiki tells that
> motorways and
> > railways can be tagged with viaduct to denote a long bridge, but this
> should
> > apply to nodes only. Does this make sense? IMHO this tag is suitable
> only for
> > ways but not for nodes. The same is true for waterway/aqueduct. What's
> your opinion?
> >
> > florian
> >
>
> I'm not aware of the history of the viaduct tag, but should it not be
> now deprecated in favour of the bridge tag?


So the question is, when does a bridge become a viaduct and indeed do they
differ. Well in theory yes, a viaduct is normally a multi span bridge, that
is a bridge that has intermediate support piers. Its not always clear though
because modern bridges over major rivers for instance are a combination of
aproach viaducts and central bridge spans

Since OSM is about getting the data correctly tagged then the use of viaduct
and bridge for the correct physical objects is wholly appropriate. Just
because a viaduct (or indeed an aqueduct) does not yet get rendered by one
of the default map renders does not mean it should not be tagged to
correctly describe the feature. Always use the most appropriate tag for the
data and try not to dwell on what that might mean for rendering.

As for what it applies to then a viaduct should definitely be on a way. A
bridge is normally applied to a way as well although arguably a single node
might be sufficient for a small feature.

Cheers

Andy

Andy Robinson (blackadder)
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