OpenStreetMap
I was trying to add layer= attributes to the ramps in this (crazy) highway junction and later went back to check how it rendered and found that osmarender seems to draw the layer=-1 roads strangely when they hit the parkland underneath.
It draws the parkland over the top of the roads -- is that intended? What is the best practice for marking these roads and parkland? The roads are in a trench and the parkland is a whole area which is defined, i believe by law.
In general I suppose part of the question is how should trenches that aren't tunnels be marked. The area of land they're in doesn't cover the roadway, so I would expect it to be rendered like a regular road.
Discussion
Comment from chillly on 31 May 2009 at 20:58
The quirk seems to have disappeared now, but looking at the complex junction there are no bridge tags. I think these would help to make it clear which piece of road is above another.
A trench that carries a road or railway is known as a cutting and is tagged as cutting=yes. I'm not sure how it renders.
Comment from stark on 2 June 2009 at 10:34
Yeah, sorry, I moved the points where the cutting started to not overlap the area.
Looking around i don't see bridge=yes being used for highway junctions generally. It seems unnecessary for people to understand the junction as long as the roads are labeled with layer= properly.
Actually I was wondering in a lot of places whether to use bridge=yes for the overpass or tunnel=yes for the underpass at intersections. I'm not sure which rendering I prefer.
Comment from stark on 2 June 2009 at 10:35
And incidentally in this junction *all* the roads would be labeled with bridge=yes (excluding the roads in the cutting past the cliff)
Comment from LivingWithDragons on 2 June 2009 at 22:14
I understand that everything is layer 0 by default, including the park. So you perhaps need to make the park layer -5.
If you do something that could be considered unusal (think by a beginner, not seeing everything so they could see a part of the park with no junction), then add a note to the way to explain why the tagging is as you've done.
Comment from stark on 2 June 2009 at 23:12
This suggestion seems like solving a rendering bug by using tagging which is specifically forbidden.
I could understand if osmarenderer implicitly assumed either cutting=yes or tunnel=yes but it seems not having a road disappear entirely seems like a bug.
I suppose it's debatable. I can think of features that perhaps you would expect to completely hide lower level roads. Obviously higher level roads for instance. Perhaps buildings? But surely not natural=cliff?
Comment from stark on 2 June 2009 at 23:13
We pretend there isn't a random extra "not" in that second paragraph.