[OSM-talk] Mapnik Rendering of Tiled Objects

Jon Burgess jburgess777 at googlemail.com
Sun Aug 12 22:51:01 BST 2007

On Sun, 2007-08-12 at 20:05 +0100, Steve Chilton wrote:
> Jon
> If I bring in lakes at an earlier zoom in the osm.xml stlye sheet is there any way that you can do any check on the effect on rendering?
> Maybe bring in at z9 only first to see, and do no other changes so that it can easily be reverted.
> Is there going to be conflict in some areas? For instance Great Lakes come in at 7,8,9 (is this data from other source)?

I had a look at Lake Superior and it seems this exists by virtue of it
being a hole in the North America polygon area as rendered by: <Style
name="world">. If you adjust the colour of this style you'll see this
effects the land-mass. Then if you adjust the <Map bgcolor="#b5d0d0"
then you'll see this changes the colour of the lake water.

The blue body of this lake disappears at zoom=10 so I suspect we will
want to shift the cutoff of this polygon and the OSM lake data
simultaneously so that we only show a single source at any given zoom.

Looking more closely I think that the rendering sources switch at the
following zooms:

 < 10 : <Style name="world">
 > 10 : <Style name="coast-poly"> & <Style name="coast-line">

... and these 2 just come from the shapefiles, not the OSM data sources.

I've never fully understood fully how the various coastal data sources
interact. I think we need to simplify them at some point. This did come
up with Artem at the party and he said he would look into using the OSM
data for coastline rendering. Maybe we need to wait and see if he comes
up with anything.


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