[OSM-talk] Key:layer update

Richard Z. ricoz.osm at gmail.com
Sun Mar 9 13:18:04 UTC 2014

On Sun, Mar 09, 2014 at 02:00:36PM +0100, Tobias Knerr wrote:
> On 09.03.2014 13:21, Richard Z. wrote:
> > the same conceptual problem exists with pylons where they are shared by two bridges
> > or aerial tramways. Actualy every pylon breaks the rule by definition because it 
> > connects "ground" with layer=0 with something else at a different level.
> > How do you want to model such cases better? Lifts in buildings?
> Typical pylons aren't a problem because the "ground" is not an OSM
> element that they could share a node with. Pylons shared between more
> than one bridge are indeed an interesting problem for 3D mapping, but
> I'm not aware that this is commonly mapped or used by applications yet,
> so there is still some room for establishing good standard practice.
> Lifts in buildings don't use layer, they use level. That tag follows
> different rules than layer.

I would be in favor of using level more widely but the rules are not so
much different because you can also have all kinds of highways and railways
on levels.

> > In practice this rule is broken more often than you would think: Hamburg is full
> > of waterways connected with roads on bridges through a tag obstacle. France is 
> > full of bridges sharing a node with the waterway bellow.
> I would prefer correcting these errors instead of changing the rule they
> break.

are those really errors? Pylons must share a node with the waterway bellow
in my opinion. They are a pretty relevant part of it.

> > It may be worth to tag have such a rule restricted for "ways of the same type"
> > and a short well defined list of exceptions.
> The rule is also needed for ways of different types, e.g. for ordering a
> stack of road, railway, and waterway bridges.

then there is the alternative of having a list of exceptions.


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