[GRASSLIST:68] Re: making a "true-color" landsat composite

[Hamish]

> I was working on constructing some "true color" landsat composite
> images today  from bands 3,2,1 -- and came across some strange
> inconsistencies. Data from  one source produces "nice" true color
> images:
> 
> http://casoilresource.lawr.ucdavis.edu/drupal/node/211
> 
> whereas, another source produces somewhat muddy true color composites.
> I tried  playing a bit with an equalized grey colormap for each band
> via r.colors  color=grey.eq with the following results:
> 
> http://casoilresource.lawr.ucdavis.edu/drupal/node/215
> 
> 
> Does anyone have any tips on how to tweak color ramps for the various
> bands so  as to get a better looking "true color" composite?

You have to set the color range 0,255

r.colors image.red color=rules << EOF
0 black
255 white
EOF

etc for all three. The color=grey rules will "zoom" to the extents of
the data. You need to force black as 0 and white as 255.

Also, i.oif is a good tool for selecting the three bands with the
greatest spectral difference. Switch out those three in d.rgb 'til it
looks best..



Hamish