Hi all,
Yesterday I experienced a strange issue while downsampling image with
gdal_translate -tr option (-filter is average). I was downsampling data
before feeding them into a stereo reconstruction processing chain, and
the output DSM had a clear and straight cutline in the middle of the
image, as if the whole south part of the image was several meters lower
than the north part. I compared the downsampled images with an in-house
downsampling tool, and found indeed that whole rectangular portions of
the gdal_translate output were a bit shifted (maybe less than a pixel,
but that counts when doing stereo reconstruction). At one point I
started suspecting my .ovr files, and indeed removing them made the
problem disappear (I was subsampling by 10, whereas overviews have been
generated with the classical 2 4 8 16 32 ... progression). So here are
my questions :
- Is gdal_translate using the nearest overview level as a start for
resampling ?
- Is there a way to prevent that (other than removing the ovr file) ?
- Is it expected than the resampling yields artifacts when ovr files are
present ?
Thanks a lot for your help,
Regards,
Julien
--
Julien MICHEL
CNES - DSO/SI/2A
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