[Gdal-dev] Warping an ecw

[Frank Warmerdam]

On 11/12/05, SteveC <steve at asklater.com> wrote:
> Hi
>
> I'm trying to transform an ecw but always get errors. Any help/pointers
> appreciated.
>
> I get
>
> $ gdalwarp -tr 0.001 0.001 -t_srs "epsg:4326" -of GTiff foo.ecw foo.tiff
> Creating output file that is 784P x 648L.
> :0.ERROR 1: NCScbmReadViewLineBIL failed.
>
> $ gdalwarp -t_srs "epsg:4326" -te 0 50 10 60  -ts 30 30 -of GTiff foo.ecw foo.tiff
> Creating output file that is 30P x 30L.
> :0..10..20...33..40...50...61..ERROR 1: NCScbmReadViewLineBIL failed.
>
> $ gdal-config --version
> 1.3.1

Steve,

I'm not sure what is going wrong.  What version of the ECW SDK are
you using?  I will warn you that even if this works, it will be very slow
since the warper will always load the source chunks at full resolution.
I gather you are wanting to use gdalwarp to dramatically downsample
the data?

You might want to try something like "gdalinfo -mm foo.ecw".
This should force one read pass over the whole file computing
the min and max.  If this fails, then we can suspect there is
something wrong with the file, or with the ECW SDK in
simple access situations.  If that works fine, then it may be
something more complex.

I have submitted a bug report to ERMapper where I had crashes in
the ECW SDK when doing many small windowed reads on a large
file.  I haven't heard back if they were able to reproduce it.   You
might be running into something similar.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent