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/[email protected]/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-
>
>
>
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