[Talk-GB] Bridges (Edinburgh)

Chris Fleming me at chrisfleming.org
Wed Aug 8 15:00:35 BST 2007

Minty wrote:
> I've noticed many bridges around Edinburgh appear to be done using
> three seperate Ways
> See "George IV Bridge", and also "Castle Terrace" if you pan to the
> left a little.
> http://tinyurl.com/298f7t
> * way_before_bridge
> * way_for_bridge
> * way_after_bridge
> all three have highway and name attributes set to identical values
> with the middle one also having bridge=yes.
> Mapnik appears to be able to deal with this, but the
> informationfreeway / tiles at home appear to get confused and render the
> street name three times (once per way), which tends to look rubbish.
> But it also seems wrong and over-complicating things to me.
> Would it not be better to have:
> * one way for the whole of the street, with highway and name set.
> * A second Way for the segments covering the bridge with the only
> attribute being bridge=yes (and name= if the bridge itself has a namereas
> distinct from the road).
> Yes/No?
No. It's complicated to draw, extra rules would need to be added to the 
renderer to define if this is or isn't a bridge. Route finding 
algorithms would get confused. I'm sure there are more reasons.

As you have pointed out, Mapnik can draw these correctly now, there is 
already a script in the osmarender4 svn directory that will 
automatically remove these, and hopefully osmarender5 will be able to 
cope even better....

If you *really* want to stop these from being disabled then you can use 
tags to stop osmarender from drawing the names: 



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