[OSM-talk] Somthing odd with the rendering of contours

Andrew Rowson openstreetmap at growse.com
Tue Oct 28 17:05:07 GMT 2008


Hi,

I'm trying to set up a Mapnik server with a transparent contours 
overlay. I've succeeded in getting the mapping data imported into 
postgis along with the contour data for the region I'm looking at. 
Initially, I imported the UK data and noticed that there were odd things 
going on with the contours in various places. Thinking this was just bad 
SRTM data, I imported the data for switzerland (so I could compare with 
OpenPisteMap) and am seeing the same thing. I've got a picture of how 
it's rendering:

http://img66.imageshack.us/my.php?image=mapky8.png

Both the map tiles and the contour tiles were rendered with the 
generate_tiles.py script. There are two issues. The first is apparent 
from the image - the contour lines aren't being rendered in some areas. 
The other I noticed when looking at my UK renderings - in some cases 
contours weren't plotted above a certain height, leading to lots of 
"plateaus" in what should be quite a hilly area.

I've rendered these both with the script and with mod_tile, redownloaded 
and imported the data and with the same result. Any ideas what's causing 
this?

Thanks,

Andrew




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