[GRASS-user] <i.landsat.trim> -- script to trim Landsat images, make footprints and all-coverage mask

Alexander Muriy amuriy at gmail.com
Thu Dec 20 23:58:34 PST 2012

2012/12/21 Nikos Alexandris <nik at nikosalexandris.net>

> I am testing <i.landsat.trim>.  Nice work!

Thanks, Nikos!

> how do we interpret exactly the  "rast_buffer"  parameter?
"rast_buffer" is the "service" parameter, which is used for several actions
with the input raster bands. First of all, it identifies the width of
raster buffer zone for making the band mask; also it controls the
resolution of region during processing. It was gained experimentally with
the best value near 300 meters for Landsat 7 images (sounds not very
logical, I understand).

> Testing on a single L5T band, I get strange (to me) results with various
> buffer
> distances (e.g., 100, 150, 200, 5000, 10000).  Where does the  buffer
>  start?
Does it start from the outer non-NULL pixels of the image for example?

Yes, the buffer start on the border of the band mask, but with the
significantly coarser region resolution. 10000

> Is it
> expected that some distance (e.g. 100) will result in an (almost) empty
> image?
Can be expected almost anything, that's why the module needs some work to
make it more logical and more usable. I already started rewriting it in
Python, along the way I'll try to complement it  and fix some functions.

Best regards,
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