> > Forget routing in caves. There's no GPS. And those who get lost without > routing apps will get lost in a cave anyway. > +1
2014-08-14 12:32 GMT-03:00 Friedrich Volkmann <[email protected]>: > On 14.08.2014 13:18, Dan S wrote: > > >>> I think that it is an obvious idea, but wiki claimed that "At the > moment > >>> there just a > >>> tag to map the entrance to a cave." despite fact that existing tags > fit well. > >> > >> No, they do not fit. Caves are complex three-dimenional structures. In > most > >> caves there are no paths. You go or climb or rope down whereever you > feel like. > > > > This is the same as with a pedestrian square - there's no specific > > route in the square and you go wherever you feel. However it's useful > > to make them part of the OSM database, both for showing their > > existence and to help with various routing applications. > > Pedestrian squares are 2-dimensional. Caves are 3-dimensional. Many cave > rooms overlap themselves a couple of times in the z-axis. > > Forget routing in caves. There's no GPS. And those who get lost without > routing apps will get lost in a cave anyway. > > > I'm afraid layer=-1 does not express that a feature is underground. It > > expresses that a feature is lower than all features at layer=0+, but > > there's no guaranteed relationship with ground level. > > In central Europe it is, but habits may vary around the word. Much chaos > these days... > > In my opinion, there is some misconception by people who are used to image > editing software such as Photoshop, Adobe illustrator, Gimp, Corel Draw, > Inkscape, etc., as well as CAD software. In all of these applications, > layers stand for rendering order. In OSM we need to think in physical > layers. > > Caves are just an example. There are many more underground objects which > are > not tunnels. E.g. I used to go to school over a landfill for 8 years > without > knowing, because it was covered with soil and grass. The only way for > renderers to know is by eveluating the layer tag. Of course you could set > some additional tag like underground=yes, but having two concurrent tags > for > the same thing is just a mess. You'll soon get a lot of inconsistencies. > > > There are quite > > a few objects with the implicit layer=0 but which are not at ground > > level (e.g. tunnel=culvert items: <http://overpass-turbo.eu/s/4zE>). > > Therefore we need to tag them all with layer<0. There was a proposal for > implicit default layer=1 for bridges and -1 for tunnels, but unfortunately > it was voted down, so we are damned to set it manually every time. > > -- > Friedrich K. Volkmann http://www.volki.at/ > Adr.: Davidgasse 76-80/14/10, 1100 Wien, Austria > > _______________________________________________ > Tagging mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/tagging >
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