[OSM-talk] Underground / hovering buildings

[David Murn]

On Mon, 2011-02-14 at 16:26 -0500, Andrew Guertin wrote:
> I have a few buildings that are not simply at ground level, and I can't
> find how to map them on the wiki.
> 
> First off, a skywalk between two buildings. Nothing fancy, although it
> does go over a road.

As said before, use building/bridge/layer.

> Second, an underground building. Connects to other buildings that are at
> ground level and have basements.

You can use the building description tags for this.  For example, say
you had a 2-level building entirely underground, which attached through
a basement to another which had 2 levels underground and 3 above-ground.

http://wiki.openstreetmap.org/wiki/File:Minlevel.svg Based on a quick
read of this picture, and simply adapting the min tags, the underground
one can be: 

building=yes
building:levels=2
building:min_level=-2
height=6
min_height=-6

Aboveground can be:

building=yes
building:levels=5
building:min_level=-2
height=30
min_height=-6

> Third, a building with a courtyard, and a basement that also extends
> below the basement.

Again, similar to above.

> Fourth a building that has been built into a cliff. At the top of the
> cliff, on top of the building, are roads and sidewalks and things.

Again, similar to above, however use layer tags to correctly indicate
what roads are above/below/level with the building space.

> Fifth, a building on a hill, with entrances variously on the third,
> second, and first floor. One of the second floor entrances leads out
> onto a "green roof", which has grass planted on it and connects to the
> ground, but reaches out farther than the hill would naturally.

You can use the same techniques of min_level and levels to indicate that
too, along with layer tag.  This isnt much different to grade separated
on-ramps where there is a way between two junctions which are at
different elevations.

> Are there accepted ways to enter any of these buildings? If there's not
> an accepted way, any thoughts on what I should do?

Im happy to be corrected or have better advice pointed out, but from my
reading, I think the tagging system I suggested would be appropriate,
even if it needed a little of tweaking.
> 
> Thanks,
> Andrew
> 
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