2012/12/17 Paul Johnson <[email protected]>: > On Monday, December 17, 2012, Clay Smalley wrote: >> >> (Of course, some of these lines run through tunnels where they are tagged >> layer=-1, and on bridges where they are tagged layer=1 correctly. The layer >> tag on these bits of track would remain untouched.) >> > > Though this layer tag is unnecessary if there isn't more than one tunnel or > more than one bridge crossing a spot.
>From a data point of view layer-tags are always necessary when 2 or more objects cross each other at different levels. For bridges and tunnels it is good practise to always set a layer tag (and mostly there will be other objects crossing, because that's the reason why there is a bridge). In the standard mapnik style there is no need to set an explicit layer tag though, so for 2 crossing objects one of which a tunnel or a bridge the rendering will be correct also if the data isn't complete. cheers, Martin _______________________________________________ Tagging mailing list [email protected] http://lists.openstreetmap.org/listinfo/tagging
