Awesome! Congratulations, i envy you. I did not want to mislead people, maybe a misunderstanding?
I wrote in my mail that my understanding did not lead to a correct image, i meant that somewhere there must be a failure in my misunderstanding. I did not want to say that gdalwarp does not work, it obviously does work. Has anybody got a hint on which of my assumptions is wrong? a. The source SRS is epsg:4362 b. The target SRS should be as in osm.xml c. Mapnik can not warp a raster image, it has to be pre-warped. d. The "world file" of my TIF file is incorrect. e. anything else? I just tried the other hint of skipping the regions around the poles, the height is 21600, which is +90.0 to -90.0. I tried to go from +85.051128 to -85.051128 (atan(sinh(pi)) as this was mentioned to be the limit of mercaator. So i skipped 593 pixels at top and at bottom and changed the world file for a strip generated like that: 0.00833507730103945403 0.00 0.00 -0.00833507730103945403 0.0 85.051128779806589 No success... I began to reproject the blue marble with an own script but there is a slight offset / scale yet. Thanks for any hints, Torsten. > Please do not mislead people. gdalwarp works fine: > > http://tinyurl.com/germany-blue-marble > > Regards > Juan Lucas > > > > > > ________________________________ > > > > > Hello Jukka, > > thanks for your hint, but to my understanding this contradicts > the description of RasterImage in Mapnik and the web page > that converts "blue marble" using gdalwarp. > > In the documentation for RasterImage it says that Mapnik > can't (yet) reproject reaster image data, they have to match > the target projection. I got that answer to another question: > > > http://www.mail-archive.com/mapnik-us...@lists.berlios.de/msg01213.html > > > So if in osm.xml there is: > > srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 > +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgri...@null +no_defs +over" > > Then i think this should be the target projection (if i want to > mix a > raster image into it). > > > The "blue marble" has lat / lon directly mapped to x / y > coordinates. > To my understanding this is similar to WGS84, to add the scaling > with a "world file" makes sense to me. > > Looking at this page i see a description of projections and > the use of > gdalwarp that describes how to get > > > http://egb13.net/2009/04/bending-the-earth-gdalwarp-and-the-blue-marble/ > > > But in the end, my understanding did not leave to a correctly > projected > image... > > > Best regards, > Torsten. > > Am Sonntag, 3. Mai 2009 14:11:06 schrieb Jukka Rahkonen: > > Torsten Mohr <tmohr <at> s.netic.de> writes: > > > Hello, > > > > > > thanks for that hint. > > > > > > Right, the chosen projection won't work around the poles, i > don't > > > expect that. In the call to gdalwarp i gave the source > projection > > > (EPSG:4326 or WGS84) and as target projection i gave the > projection > > > used in osm.xml. > > > > Hi, > > > > Your target projection is the so called Google projection, or > > epsg:900913, or nowadays officially epsg:3785. It is the > projection > > used in OSM slippy map, but the native OSM data are in > epsg:4326. > > Therefore you should warp the downloaded images _into_ > epsg:4326, not > > from that. Unfortunately I cannot say what would be the > correct source > > projection definition for your original images. > > > > An easy way to test your warped images is to download some > OSM data in > > shapefile format and in epsg:4326 projection from > Geofabrik.de, open > > the warped image with some GIS program like QGis or OpenJUMP > together > > with OSM shapefile and see if they suit well together. > > > > Gdalwarp options are documented at > http://gdal.org/gdalwarp.html but > > some further reading may be necesssary to understand what all > the > > options mean. > > > > -Jukka Rahkonen- > > > > > > > > _______________________________________________ > > talk mailing list > > talk@openstreetmap.org > > http://lists.openstreetmap.org/listinfo/talk > > _______________________________________________ > talk mailing list > talk@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
