[talk-au] Playing with transparent layers

[John Smith]

While playing round with mapnik style sheets I came across a noname
style sheet which makes a red line for the way:

http://beta.letuffe.org/mapnik-styles/noname.xml

I extended it a little by making it render up to z7, and it also
ignores unnamed roundabouts:

http://maps.bigtincan.com/?z=7&ll=-27.496,152.998&layer=B00000000TFFFF

It's not surprising that the areas with the most unnamed streets also
have the most aerial imagery available.

The reason I played with this style sheet was due to people
complaining about the time it takes CloudMade to refresh their nonamed
tiles, I have the server setup to be z0-z8 expire once a week, z9-z12
expire in 2 days and z13-z18 expire in 4 hours.

I was expiring tiles in real time but the application to handle that
runs on a single core so the server ended up getting behind well
behind in updates at times, I would have thought a lot more of the
tile stuff would have been multi-process or at least multi-threaded.