[Tagging] Are tunnels only below ground? (Was

[Randy]

Anthony wrote:

>On Wed, Nov 4, 2009 at 7:56 PM, Randy 
><rwtnospam-newsgp at yahoo.com> wrote:
>>Anthony wrote:
>>
>>>On Wed, Nov 4, 2009 at 10:03 AM, Anthony
>>><osm at inbox.org> wrote:
>>>>On Wed, Nov 4, 2009 at 6:22 AM, Martin Koppenhoefer
>>>><dieterdreist at gmail.com> wrote:
>>>>>2009/11/4 Richard Bullock 
>>>>><rb357 at cantab.net>
>>>>>>
>>>>>>A passageway through a building (but, say, without being inside that
>>>>>>building) is, to all intents and purposes, a tunnel.
>>>>>
>>>>>a passageway through a building that is not inside that building will 
>>>>>be
>>>>>hard to find. (how do you define: is not inside?)
>>>>
>>>>http://maps.google.com/maps?oe=utf-8&client=firefox-a&ie=UTF8&q=mosi+tampa&fb=1&gl=us&hq=mosi&hnear=tampa&cid=0,0,4145233176872570172&ei=kpbxSpL3BtTY8Aa95d2MCQ&ved=0CA0QnwIwAA&ll=28.054341,-82.404791&spn=0,359.981289&t=h&z=16&layer=c&cbll=28.054341,-82.404885&panoid=utISmaJ6ph__dBBezFDBpQ&cbp=12,185.93,,0,0.05
>>>>
>>>
>>>Currently tagged as a "tunnel", although positioned incorrectly
>>>(http://www.openstreetmap.org/?lat=28.05335&lon=-82.404758&zoom=18&layers=B000FTF).
>>>
>>>Which is fine, as long as the definition of tunnel is changed.  The
>>>definition needs to be changed, because I don't want my routing device
>>>to tell me to "make a right and go through the tunnel".  And I don't
>>>want dotted lines when these passages are rendered - because if I look
>>>at that I'm going to expect something that goes underground, and I'm
>>>going to be confused when there's no tunnel, but just a building which
>>>was built over top of a road.
>>
>>From the picture, it appears that where the road is covered by the
>>building there is actually a pedestrian way and doors into the building
>>from the highway. If that's the case, then it is clearly not a tunnel, be
>>it above or below ground.
>>
>>How would you like to see something like that rendered besides dashed. Oh,
>>you said not dotted. Is dashed OK?
>
>No.  I don't really know if this is considered dashed or dotted, but
>to me, the dashed/dotted lines in this image represents a tunnel, not
>a road with a building (or other road) over top of it:
>http://wiki.openstreetmap.org/images/e/e0/Mapping-Features-Road-Tunnel.png
>
>I'm not sure that the situation at the Tampa MOSI has to be rendered
>any differently than any other road.  The road itself is just a normal
>service road.  If you do want to render it differently, that's fine
>too, but then choose something new - don't render it the same way as
>something else (like a tunnel), because that's confusing.
>
>For the proposal, apparently we're supposed to choose a rendering
>style (personally I don't even like this - the renderers should choose
>how to render, the mappers should just provide them with unambiguous
>data, i.e. not tagging a tunnel and a non-tunnel with the same tag).
>I proposed "use a fill pattern" to represent the cover.  But for this
>situation, I'd prefer Martin's proposal: "the way is a normal way and
>map the building".  The building should be partially transparent, so
>that the way can be seen underneath it, of course.
>
>Anthony

That, to me, is clearly rendered as a tunnel, because it shows the ports 
into the tunnel. A way that is going under another object such as a 
building does not need the ports rendered, since the edges of the covering 
object would, presumably be at or near the point where the way is covered.

If semi-transparency works in all cases, then that would be fine. My only 
concern would be if the normal way is rendered as something without fill, 
it might be very difficult to determine whether it was semi-transparent or 
not. Actually, you would want to make the way semi-transparent, which 
should visually provide the same effect. You wouldn't want to make all of 
the building semi-transparent, I would think.

And, I tend to agree with you. I see the proposal rendering style as 
strictly suggested, and probably not worth spending a lot of time on. The 
renderers probably should determine the rendering style, once they 
understand the purpose of various tags. And, obviously they do, as 
demonstrated by the significant differences in the currently available map 
renderings. That, to me, is as it should be.

-- 
Randy