[gdal-dev] Unexpected behavior with gdal_merge.py

[Roger André]

Just a quick question to ask for an explanation regarding something I've
just seen in gdal_merge.py.  I have 6 tiles arranged in 2 columns, and which
I've mosaic'd together.  I was asked to re-register the tiles in the 1st
column by 1/2 a pixel SW.  I've done this, and in openev I can see that the
individual tiles are shifted SW, thereby causing a gap to appear between the
2 columns.  All good, and what I expected.  However, when I mosaic the tiles
together with gdal_merge.py, there is no gap, and it actually appears as
though the tiles in the 2nd column have been shifted to fill the gap.  Is
this to be expected?  I've read that it is possible to mosaic tiles together
using gdalwarp, but I'm not sure how to do this.  If I used gdalwarp
instead, would I have the expected gap?

Thanks,

Roger
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