[OSM-talk] tagging and rendering highways in the USA and elsewhere

Martijn van Oosterhout kleptog at gmail.com
Fri Apr 18 21:55:40 BST 2008


On Fri, Apr 18, 2008 at 9:02 PM, Tom Hughes <tom at compton.nu> wrote:
>  I was thinking about that while I was walking home earlier. The
>  main question I guess is how efficient PostGIS is at answering
>  the question "which of these N hundred polygons is this data
>  in", or how efficiently we can code the equivalent in osm2pgsql.

Getting osm2pgsql to do it on insert wouldn't be too hard once you
have a table of polygon. Biggest problem is going to be that it's
going to slow everything down a lot.

However, when we get so far that osm2pgsql can process just diffs,
then you only have to do it once and after that the load will be quite
managable...

>  Indeed. I was thinking about that too, and I think it needs an
>  extrat level of indirection, so the existing stylesheet stays
>  largely as it is but instead of saying that a secondary road
>  is rendered as #213455 or whatever some sort of code name is
>  given and then that is mapped to the real colour based on the
>  country.

Yeah, either mapnik needs to handle this (perhaps some kind of lookup
table indirection), or we have a script that takes the current sheet
and a list of (country code,tag,colour) and produces a much bigger
file with all the changes...

Have a nice day,
-- 
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/




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