[Tagging] Tunnels and bridges

[Tobias Knerr]

On 01.02.2013 09:49, Martin Vonwald wrote:
> 2013/2/1 Tobias Knerr <osm at tobias-knerr.de>:
>> On 01.02.2013 07:22, Martin Vonwald (imagic) wrote:
>>> We have a spatial database so if all features are within a closed way there is no need for a relation. Why is there a different reasoning for a bridge?
>>
>> Because it is usually _not_ the case that all the features within the
>> bridge outline polygon belong to the bridge.
> 
> For example? And I'm talking about features on the same level/layer.

That's exactly the additional qualifier not present with the waterpark.

But if we clearly define that
- they must be on the *same* layer (==, not >=)
- this layer must be explicitly tagged on the bridge itself
- this layer must be explicitly tagged on all elements
- ways must be split at the beginning and end of the bridge
then the situation is probably still clear enough for data consumers.

If I understand your reply to Steve today correctly (man_made=bridge
outlines for one-level bridges), then you would be fine with requiring a
relation for anything more complex, such as multiple levels or
individually mapped piers and so on?

In that case, this should be compatible with the rules outlined above,
so if these are documented in this way I would be fine with it.

Tobias