Am 08/feb/2012 um 17:03 schrieb John Sturdy <jcg.stu...@gmail.com>:
> On Wed, Feb 8, 2012 at 12:40 PM, Martin Koppenhoefer
> <dieterdre...@gmail.com> wrote:
>
>> 5. building:min_level=* Number of stories between ground and actual
>> first existing floor
>> -> I'd completely discourage usage of this key, and suggest to
>> estimate the elevation of the lowest part of the building.
>
> This needs to take into account that some buildings are built on
> sloping ground, and the floor which is at ground level on one side of
> the building may not be on ground level at the other side.
Yes, this is a general problem here: reference elevation. I have thought about
this, because if there are several building parts they might have different
elevations to which there heights refer to.
One solution might be to expressly tag this reference height. In Architecture
you'd normally set the reference +-0.00 elevation in respect to a given ground
elevation (which you choose freely, normally a point on the road, and which is
given in the local height system). All other elevations are then relative to
this 0. Each distinct object would have this reference height (it's 0.00 in
WGS84) and it could even differ from the 0.00 of other building parts of the
same building. This is essential as otherwise changing the ele of one object
would have influence on the heights of other objects.
Cheers,
Martin
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