Alright. I see that "applying layer to long ways" is bad for several reasons. Surely this could be turned into a validation warning.
But what's the difference between tagging the bridge with layer=1 and tagging the river underneath with layer=-1? Some people seem to think that both are necessary, many think it's best to use layer=1 on the bridge, I'm saying that layer=-1 on the river (let's say a short section, not the entire length) is "equivalent". Is it not equivalent? Is it wrong? If it is wrong, why is it wrong? On Sat, Mar 15, 2014 at 12:53 PM, Frank Little <frank...@xs4all.nl> wrote: > Martin Koppenhoefer wrote: >>> >>> Am 14/mar/2014 um 15:51 schrieb Fernando Trebien >>> <fernando.treb...@gmail.com>: >>> >>> Do you agree that the river can be tagged with layer=-1 as long as >>> this value is correct in relation to the layer of other >>> nearby/crossing ways? >> >> >> I would discourage you to do so. Layer tags should only be applied to ways >> that actually cross other objects on different layers (ie without >> intersecting them). >> > I agree totally with: "Layer tags should only be applied to ways that > actually cross other objects....." > > At its simplest, a layer tag is a hint to a renderer which of two crossing > ways should be rendered later (i.e. on top). If a renderer does not apply > the real world knowledge that a bridge (by its definition) crosses over a > way (road, water, whatever) underneath, then it can still take the hint to > render it correctly. The renderers have no problem interpreting the > situation correctly, with or without the layer tag, afaik. > > A layer tag is not a way to define the relative height of different objects. > Some of the discussion on the proposal's talk page is confused about that. > > I would tag the structure (bridge or tunnel) with a layer tag*. > I would not tag a river or stream along its entire length. > > Rivers, streams, canals, etc. are surface features (in most cases). The mere > fact that the bed of a waterway is often at a lower level than the > surrounding ground level is not relevant for the layer tag since hinting for > correct rendering is not necessary. (In the Netherlands and other polder > areas, waterways are often above the surrounding area.) > > *Actually, as I made clear on talk when we had this discussion very > recently, I would prefer not to use the layer tag at all in most of these > cases. The fact that somewhere between one quarter (taginfo) and one third > (overpass turbo samples in the Netherlands) do not use a layer tag with > bridges indicates to me that it is not as clear cut as people are > suggesting. (Note: I realise that there are specific cases where explicit > tagging for layer hinting is necessary (e.g. bridges or viaducts layered > vertically). These are relatively rare.) > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging -- Fernando Trebien +55 (51) 9962-5409 "The speed of computer chips doubles every 18 months." (Moore's law) "The speed of software halves every 18 months." (Gates' law) _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
