[OSM-talk] Ditches

[Peter Childs]

2009/12/15 John Smith <deltafoxtrot256 at gmail.com>:
> 2009/12/15 Steve Bennett <stevagewp at gmail.com>:
>> IMHO, tagging "layer=1 bridge=yes" for a road going over water is an
>> example of a hack, and "tagging for the renderer". The information
>> "bridge=1" is more than enough to render with, so "layer=1" can *only*
>> be interpreted as giving a renderer a crutch.
>
> Without layer information you'd be guessing if the road goes over the
> water or the water goes over the road, or the water and road are at
> the same level.
>
> You could come up with sane defaults, but that's making assumptions
> rather than tagging explicitly so you know beyond a reasonable doubt.
>

If you have a bridge or a tunnel you don't need a layer tag a bridge
infers it "goes over" a tunnel that it "goes over"

If there is neither a tunnel, or a bridge and no layer either then it
must be a ford.

If you mark bridge=yes, layer=1 you are repeating your self. which is
where problems start, see database normalisation.

Peter.