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
