[gdal-dev] gdalwarp trunk and FWtools giving different results

[Joaquim Luis]

Testing with RC2 shows that the wrong result persists like with the 
trunk version.

with a small variation now
gdalwarp -s_srs "+proj=merc +R=6371008.7714" -t_srs "+proj=latlong 
+datum=WGS84" alg.tiff alg_geo.tiff

I have put the file at
ftp.ualg.pt/users/jluis/alg.tiff

Shell I file a ticket saying that gdalwarp is broken when converting 
from Mercator?

Joaquim Luis

> Hi,
>
> I am very puzzled with this difference between the outputs of gdalwarp 
> form a couple of days old Trunk version versus FWtools 2.2.0
>
> In both cases the command is the following
> gdalwarp -s_srs "+proj=merc +R=6371008.7714" -t_srs EPSG:4326 alg.tiff 
> alg_geo.tiff
>
> but the trunk version has
>
> Upper Left  (  -8.0862815,  37.3460021) (  8d 5'10.61"W, 37d20'45.61"N)
> Lower Left  (  -8.0862815,  37.0644230) (  8d 5'10.61"W, 37d 3'51.92"N)
> Upper Right (  -7.7343076,  37.3460021) (  7d44'3.51"W, 37d20'45.61"N)
> Lower Right (  -7.7343076,  37.0644230) (  7d44'3.51"W, 37d 3'51.92"N)
> Center      (  -7.9102945,  37.2052125) (  7d54'37.06"W, 37d12'18.77"N)
>
> whilst  FW
>
> Upper Left  (  -8.0862815,  37.1605907) (  8d 5'10.61"W, 37d 9'38.13"N)
> Lower Left  (  -8.0862815,  36.8792107) (  8d 5'10.61"W, 36d52'45.16"N)
> Upper Right (  -7.7339340,  37.1605907) (  7d44'2.16"W, 37d 9'38.13"N)
> Lower Right (  -7.7339340,  36.8792107) (  7d44'2.16"W, 36d52'45.16"N)
> Center      (  -7.9101077,  37.0199007) (  7d54'36.39"W, 37d 1'11.64"N)
>
> Note the differences in latitude.
> The FW solution, as far as I can tell from plotting a coastline, is 
> the correct solution.
>
> What can explain those differences.
> NOTE, I do have GDAL_DATA pointing to the SVN data directory
>
> Joaquim Luis
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