[GRASS-dev] Landsat 5TM pre-processing - histogram matching - problem

[Moritz Lennert]

On 04/05/15 11:28, joanna mardas wrote:
> Hello,
>
> I'm totally new user of GRASS and of course I have some problems. I want
> to do the pre-processing of Landsat (5TM) images (for further band
> composite, classification and NDVI) and I was using the tips from
> http://grasswiki.osgeo.org/wiki/LANDSAT#Pre-Processing I did the
> *i.landsat.toar* I wanted to do the i.atcorr as well but I have no idea
> how to do this, the manual was not helpful for me, so I gave up. I did
> not do i.topo.corr because the land I'm working on is flat.
>
> And I really want to do "/radiometrically normalise → one approach
> via*i.histo.match* (in grass 7), also known as relative radiometric
> normalisation -- one approach is the histogram matching technique of two
> or more raster maps/". I have fragments of original landsat images
> imported to GRASS and i.histo.match works with them without any
> problems. But there is a problem when I want to do this on images which
> I got after i.landsat.toar. The output images are monochromatic-one
> colour. I've used command i.histo.match
> input=_toar2 at konfa,86_toar2 at konfa (the input files are those which I got
> after i.landsat.toar) and then r.colors map=86_toar2.match at konfa
> color=grey. I thought that those steps from grasswiki should be done
> "step by step", so first i.landsat.toar, and then on the output files
> i.histo.match.
>
> Does anyone know how to do this in a proper/correct way?

ISTR that i.histo.match works with integer imagerie, i.e. recoded to 
0-255. Recode your toar images to that range with r.recode and try to 
run the result through i.histo.match to see if that helps.

Moritz