[OSM-newbies] Road below a building

[Randy]

Renaud MICHEL wrote:

>Le jeudi 29 octobre 2009 à 13:22, Richard Weait a écrit :
>>We aren't really discussing the main building in this case are we?
>>More like an awning or a car port?  How do we generalize this so that
>>it applies in a sensible range of use cases?  Multi-lane drive-up
>>banks and multi-lane gas stations come to mind as well as drive-in
>>restaurants. [1]
>
>And even restaurant over motorways, see this one
>http://maps.google.com/?ie=UTF8&ll=50.654555,5.710015&spn=0.004673,0.008873&t=k&z=17
>which doesn't show very well in OSM either
>http://osm.org/go/0GAA7tEY1-
>
>>I suggest that any tagging on the way should be reduced.  With the
>>exception perhaps of maxheight. Leave layer for when a motorway passes
>>over a carport access road.
>
>Why limit layer usecase to roads?
>It seems appropriate for any features laying at different altitude on the
>same (horizontal) position.
>And the wiki page[1] says that it can be used for area as well, only
>landuse-like areas are excluded.
>
>[1] http://wiki.openstreetmap.org/wiki/Key:layer

Richard and Renaud,

In my original case, my example was the cover extending from a building, 
over a drive-up bank. Conceivably I could map the extention separately 
from the building, put it at layer=1, and create a building relation of 
the two. However there are cases where the building, including the part 
over the road is much more integrated, and can't accurately be broken 
apart. In a case like this, where the building is based at level 0, as is 
the road and parking area. I would use the "covered" tag to denote that 
the service road proceeds under, not over the building. If I set the road 
at layer=-1, it would falsely indicate that the road is below the 
surrounding parking and pedestrian areas. If I set the building at 
layer=1, then the first floor is not at the pedestrian and road access 
level. Using "covered" I don't have to falsely state that there is a 
diffence in levels.

Yes, layers can certainly be used for many different objects besides 
highways. In this case, using layers leads to a false or confusing 
representation of the physical world.

In my opinion, using "covered" to indicate that a highway (road, path, 
waterway, etc.) goes under something but is not in a tunnel would be a 
viable option, especially when it is not physically accurate to separate 
the system into layers.

-- 
Randy