My first guess would be that Mapnik is unable to reproject the osm data into UTM because the osm layers extents are not valid for UTM.
If this is the case, then this is partly a bug in Mapnik and party a condition of trying to project global data into a local projection. See the thread linked off of http://trac.mapnik.org/ticket/549 for more details. Short of trying to apply that patch you could try setting the 'extent' parameter for all your osm layers in the osm stylesheet to: '11.03,49.42,11.13,49.48' Let me know if that helps. If not let me know what osm extract you used and I can try to test locally. Dane On Jun 2, 2010, at 1:24 AM, kfr wrote: > > Hello everybody! > > I'm trying to render some maps of the same area using different projections > in order to compare the rendered images with each other. I.e. i defined an > area and rendered the data from that area using e.g. UTM zone XY projection, > google projection, and so on... In order to get the job easily done i wrote > this little python script: > > (Note: my system is Ubuntu 10.04 as explained here > http://weait.com/content/build-your-own-openstreetmap-server > http://weait.com/content/build-your-own-openstreetmap-server , the > projection definitions come from http://www.spatialreference.org/ > http://www.spatialreference.org/ ) > > > #!/usr/bin/python > import mapnik > > mapfile = "osm.xml" > > projections = { > "latlon": "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs", # > EPSG:4326 > "utm_32n": "+proj=utm +zone=32 +ellps=WGS84 +datum=WGS84 +units=m > +no_defs", # EPSG:32632, > "google": "+proj=merc +lon_0=0 +lat_ts=0 +x_0=0 +y_0=0 +a=6378137 > +b=6378137 +units=m +no_defs", # SR-ORG:95 > "mercator_world": "+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 > +datum=WGS84 +units=m +no_defs", # SR-ORG:16 > } > > ll = (11.03, 49.42, 11.13, 49.48) > > imgx = 1000 > imgy = 1000 > > # Render an image for every projection > for projName, projDef in sorted(projections.items()): > > print "Projection: " + projName > > # Load the map data > m = mapnik.Map(imgx, imgy) > mapnik.load_map(m, mapfile) > > # Override projection defined in osm.xml > m.srs = projDef > > # Calculate projected boundaries > prj = mapnik.Projection(projDef) > c0 = prj.forward(mapnik.Coord(ll[0], ll[1])) > c1 = prj.forward(mapnik.Coord(ll[2], ll[3])) > > # Apply bounding box > bbox = mapnik.Envelope(c0.x, c0.y, c1.x, c1.y) > m.zoom_to_box(bbox) > > # Render image > im = mapnik.Image(imgx, imgy) > mapnik.render(m, im) > view = im.view(0, 0, imgx, imgy) > view.save(projName + ".png", "png256") > > > But here comes my problem: the UTM projection (called 'utm_32n' in the > script) doesn't render the image i expected! Instead i only get a ocean-blue > image. All the other projections work fine! This is quite annoying and > frustrating, as the UTM projection is the most important one for my project. > > I googled through the whole internet and counldn't find any clue why the UTM > projection won't work while all the others do... > > So if anyone can give me a hint i would be very thankful!! Perhaps i > misunderstood som facts, have missed something, etc.... > > I uploaded the resulting images for all four projections: > > longlat projection: > http://old.nabble.com/file/p28751475/latlon.png > > google projection: > http://old.nabble.com/file/p28751475/google.png > > mercator projection: > http://old.nabble.com/file/p28751475/mercatorworld.png > > utm projection: > http://old.nabble.com/file/p28751475/utm32n.png > > Greetings from Germany... > -- > View this message in context: > http://old.nabble.com/Problems-with-some-Mapnik-projections-tp28751475p28751475.html > Sent from the Mapnik - Users mailing list archive at Nabble.com. > > _______________________________________________ > Mapnik-users mailing list > [email protected] > https://lists.berlios.de/mailman/listinfo/mapnik-users _______________________________________________ Mapnik-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/mapnik-users
