How to fix strange rendering behaviour of OSM Data in Mapnik?

Question

My current setup so far is a running Apache webserver with tilecache.cgi script and a mapnik rendering engine connecting to my postgis database containing my OSM data.

The problem is very easy to describe. All roadnames, roadnumbers, descriptions are to close to each other. I set up tilecache with MetaTile=true, TileSize=8x8 and it doesn't change. What am I doing wrong?

Thanks!

Answer 1

If the problem is the name for "Rue de l'Abbe Bovet" (you're most likely rendering the OSM data from here) is appearing twice, I don't think there's a problem with the data (it's a single object in OSM, see here but rather the renderer (mapnik/tilecache).

As suggested in the comments (by Michael Markieta) check your TextSymbolizer definitions. The relevant attribute is called spacing E.g.:

<Rule>
<Filter>[highway] = 'tertiary'</Filter>
  &maxscale_zoom17;
  &minscale_zoom18;
  <TextSymbolizer name="name" ... placement="line" spacing="500"/>
</Rule>

would cause tertiary road labels to be repeated every 500 pixels.

Another thing that may be worth tinkering with is mapnik's parameter called buffer_size. I'm not sure how this works in tilecache (I've only used it in the python mapnik extensions).

As far as I remember what buffer_size does is: whenever mapnik renders something it looks at whatever is rendered through a window of buffer_size - if you want mapnik to realize it has to avoid painting a label because it's already there the label candidate and the already painted label have to coexist within the same rendering window.