Am 18.12.2012 07:31, schrieb A.Pirard.Papou:
On 2012-12-17 22:16, Martin Koppenhoefer wrote :
2012/12/17 A.Pirard.Papou <a.pirard.pa...@gmail.com
<mailto:a.pirard.pa...@gmail.com>>
We badly need precision.
. In fact, the only effect of assigning a layer is that upper
layer objects hide lower layer ones (it's not a "mind your step"
warning ;-))
it is a way to describe in the database which object is above which
or whether they are at the same level.
Agreed. And this is why I said that the tag should be called level.
Transforming that into layers is a renderer's matter that is strictly
forbidden to speak about. Yet...
possible - but its a historical evolution you have to 'correct' then.
And I (and possibly others too) see the key 'layer' differently, see below.
I have traced lengths of streams
* stream as a constant layer=-2 way, uninterrupted end to end
(even if they "don't look so deep"),
* roads are at level 0
* and bridges and culverts at level -1, in the manner mentioned
above.
very strange way of mapping IMHO, how did you come to this idea?
Exactly as you say above. They are the actual relative levels of
these objects.
I have never seen a bridge sitting on a road (and hiding it, even just
as a hint).
Well, so you just understood the layer key as 'a level of the physical
object'
whereas in my opinion the layer key is defined as 'a level of a map
feature (OSM object)'.
Physical 'level' is described best by ele (elevation, absolute) or may
be by the key 'level' (as in buildings, relative).
The key 'layer' is just a relative hint for renderer - at least in my
opinion.
Bridge and the 'road element' may be seen as different physical objects.
But in OSM bridge and 'road element' are seen as one object (one OSM
way) as long as no bridge relation is used.
So you are just not able to divide them in different OSM layers therefor
- at least not until you map different 'layer' for bridge and road
element then.
Regards
Georg
_______________________________________________
Tagging mailing list
Tagging@openstreetmap.org
http://lists.openstreetmap.org/listinfo/tagging
