[Tagging] Mapping cave tunnels passable by human

John Packer john.packer7 at gmail.com
Thu Aug 14 15:49:14 UTC 2014


>
> 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 <bsd at volki.at>:

> 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
>
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