[OSM-dev] Mapnik layer has become confused by layers?

Tom Hughes tom at compton.nu
Fri Feb 13 08:41:40 GMT 2009

D Tucny wrote:

> Not sure when this started, but, mapnik seems to be getting layers wrong 
> when drawing objects...
> e.g.
> http://www.openstreetmap.org/?lat=30.297629&lon=120.155582&zoom=18&layers=B000FTF 
> <http://www.openstreetmap.org/?lat=30.297629&lon=120.155582&zoom=18&layers=B000FTF>
> In this view there is a two dual carriageway primary roads that meet at 
> a junction at ground level (no layer tag), above the junction running 
> north south is a dual carriageway trunk elevated road/viaduct (layer=2), 
> above the primary roads, with some below the trunk and some above is a 
> junction consisting of a number of trunk_link roads (various layer tags) 
> linking the east west primary road to the trunk road... Mapnik appears 
> to be currently drawing all trunk_link roads below everything else, even 
> though they are tagged with layer tags of 1, 2 and 3 depending on which 
> other ways they pass over, though it's difficult to see if it's drawing 
> them under the trunk as there are no borders visible making it all 
> appear to be at the same layer...

It's nothing new, it has always happened. It can be fixed (as I think it 
has been for motorways) but it causes a huge explosion in the number of 
style rules to cope with all the combinations so hasn't been done more 
widely yet.


Tom Hughes (tom at compton.nu)

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