[gdal-dev] gdalwarp and Molleweide projections

[Roger André]

Hi Matthew,

It would be useful to see what your source image looks like.  I have an
image that covers essentially global extents, and which is in EPSG:4326.  I
did a reprojection using gdalwarp in GDAL 1.6.1:

$ gdalwarp -s_srs "EPSG:4326" -t_srs "+proj=moll +lon_0=0" infile outfile

The results that look reasonable, or at least I see no horizontal flipping
or other artifacts in the result.

Any chance you could share a reduced resolution version of the data with the
list?

Roger
--



On Sun, Jul 5, 2009 at 11:04 AM, Matthew Vavrek <mattvavrek at hotmail.com>wrote:

> I have just started trying to use gdalwarp and gdal_translate to reproject
> some world maps. I have managed to achieve some limited success with some
> projections, but I seem to get strange results with my images, especially
> with Mollweide. The Molleweide gives a horizontally flipped image, sometimes
> with an unreversed strip in the middle, and the top and bottom of the image
> seem stretched rather than compressed as I would expect. The code I used to
> translate is:
>
> gdalwarp -of GTiff -s_srs EPSG:4326 -t_srs EPSG:54009 input.tif
> moll-output.tif
>
> I also tried with -t_srs '+proj=moll +lon_0=0'.
> My initial image was a plain jpg, and I have tried creating a world file
> and using gdal_translate to georeference the image. I also tried using:
>
> gdalwarp s_srs EPSG:4326 t_srs EPSG:4326 input.tif output.tif
>
> to see if that would help, which it oddly did for some of the other
> projections I was trying (like polyconic). I have even tried different world
> map images, yet still get these strange results. I can't figure out what I'm
> doing wrong to get these totally bizarre images, so any help would be
> appreciated.
>
> Thanks
> Matthew
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