Fair points ... If it really doesn't matter to routers and other mappers and doesn't interfere with anything else then I am happy to accept that there is no fully logical solution and that it shouldn't matter to me either!
Mike Harris > -----Original Message----- > From: Steve Bennett [mailto:stevag...@gmail.com] > Sent: 15 December 2009 11:18 > To: Mike Harris > Cc: openstreetmap > Subject: Re: [OSM-talk] Ditches > > On Tue, Dec 15, 2009 at 8:07 PM, Mike Harris > <mik...@googlemail.com> wrote: > >> Layers are only there to explain the relative heights of > things when > >> they meet. No harm will result from marking the ditch as layer -1. > > > > See my separate reply - I disagree - what happens when the > "level=-1" > > ditch runs downstream into a "level=0" stream / river - > without a waterfall? > > Asbolutely nothing. You're waaaay overthinking this, both of you. > Layers are just a hack to make stuff render. It's not like > "bicycle=no" or something where we're making some statement > of fact about the real world. Layers are *not* a statement of > fact. Layer=3 does not, in the absolute, mean anything > different from Layer=2. > > > > >> Whether or not it needs to be a lower number than that of > the bridge > >> is an unresolved question. > > > > I disagree - surely the bridge is above the water in the > ditch and so > > - by your own defintion ('relative heights') it must have a > higher level value? > > You're trying to apply some sort of intuition or logic to this. Don't. > It's not some logic puzzle where the layers all have to mean > something. I've worked in areas where someone, for some > reason, has tagged all the bike paths in a park as layer=1. > It didn't matter. I eventually deleted the layer tags because > they interfered with my own tagging scheme, but it was > nothing more than personal preference. > > >> Not sure I'd even mark it "barrier=ditch" after all that. I'd also > >> only specify a layer for the bridge, not the ditch/drain. > > > > Agree - enough to mark it as a stream or, if that is felt > to be too 'big' > > then waterway=ditch. > > I doublechecked the wiki, looks like "barrier=ditch, waterway=drain" > might be the right way to go. Belt and braces, you know. > > > Also agree that the bridge, rather than the ditch, should carry the > > layer tag (see my comment above). > > It. Really. Doesn't. Matter. :) > > Say you have a stream at layer=3, and somewhere else it > crosses a big complicated bridge which for some reason > someone has tagged layer=-2. > You know what you do? You don't panic. You break the stream, > you set the new part as layer=-3, and you carry on. > > >Doesn't this rather imply that the ditch has the same layer > value as > >the level=0 surroundings (as I suggest) rather than > > level=-1 (as per your 'no harm' suggestion) - and that the > bridge has > >a layer value higher than 0, so presumably level=1 (as I suggest)? > > Overthinking. > > I am curious to know if any routers look at layers when you > have something like a big routable area (eg, > highway=pedestrian) with barriers within it, though. > > Steve > > > _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk