[OSM-talk] Preview: national cycle network map

Dave osm.list at randomjunk.co.uk
Thu Jul 19 11:49:57 BST 2007

> NB: there are some inconsistencies z-values at present. Look where route 4 comes into NE of Richmond Park (can't do URL to it) first (unclassified?) road is above and when swings south the road (service?) is below.

The highlights are currently being plotted just after each road, in
the same mapnik layer. This means the z-order of the roads imported
into the database determine the above-below bits... this obviously
needs fixing and it shouldn't be difficult.

I think the specific bit you're talking about is where there is a
cycleway by the side of the road -- the default mapnik rules draw the
road on top of the cycleway, so you can't see that it's there. This is
what andy was saying about changing the z-order to put cycleways on

> There are artefacts where "sections" of red/blue butt up, which multiply in sections are very short. Is this because of transparency? Can you look at that? At first I thought they had some special significance. In my view it detracts from smooth visualising of the routes.

Yeah, that's because they're transparent. I don't know if it's
possible in Mapnik to draw them all into a layer at 100% opacity, and
then composite the layers with transparency -- if there is then that
would fix this. If not, then it's a bit tricky.

> Maybe Artem could answer directly on shield/shift issues.

I'm gonna have to get onto the mapnik mailing list at some point
because I can't get the trunk version to compile at all... 0.4.0
worked just fine...

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