[Gdal-dev] Fwd: plate carree to latlon projection problem

[Frank Warmerdam]

jjknoops at netscape.net wrote:
> Hi Sjur,
> 
> Thanks for your replay. I think you are right when saying it's caused by 
> ellipsoid. So I have used this command to reproject
> 
> /call gdalwarp -s_srs "+proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 
> +ellps=sphere +a=6378137.0 +es=0.0 +units=m" -t_srs "epsg:4326"
> 
> /After comparing this result with previous results then I would say it's 
> worse. The offset between the result from gdalwarp and erdas has 
> increased. My college has also compared the results with envi and found 
> that it's comparable to the erdas results.

Jaap,

Try:

gdalwarp -s_srs "+proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0
    +a=6378137.0 +b=6378137.0 +units=m +towgs84=0,0,0" \
    -t_srs "+a=6378137.0 +b=6378137.0 +towgs84=0,0,0" ...

This attempts to do a warp from a projection on a spherical ellipsoid
to geographic coordinates on the same ellipsoid.

Note, using +a and +ellps will conflict and isn't a good idea.  And +es
is not recognised by GDAL's proj.4 parser which is not a complete proj.4
parser.

Best regards,
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