[OSM-talk] When is a bridge not a bridge?

Iván Sánchez Ortega ivan at sanchezortega.es
Thu Jan 22 15:45:32 GMT 2009

El Jueves, 22 de Enero de 2009, David Earl escribió:
> I know I'm likely to hear wildly contradictory answers and
> there's probably no right answer.

Here's mine:

You should tag things with a new layer= tag whenever thy form a different 

Think of the earth as a big (pseudo-)spherical surface. That's layer 0. Now 
put a bridge anywhere. You can either stand on the earth surface, under the 
bridge (layer 0), or on the bridge, over the earth surface.

Technically, another layer exists whenever it would be possible for a 
physical, inanimated, heavy object to freely stand at the same set of 
latitude-longitude coordinates, but at different elevations.

So, about the ramps in your theoretical bridge... are they supported on a few 
tons of dirt, or on top of concrete pillars?

Iván Sánchez Ortega <ivan at sanchezortega.es>

MSN:i_eat_s_p_a_m_for_breakfast at hotmail.com
Jabber:ivansanchez at jabber.org ; ivansanchez at kdetalk.net
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