On Wed, Jan 28, 2015 at 10:34 PM, Micha Silver <[email protected]> wrote: > When I use r.composite to create, i.e., a false_color composite from three > Landsat bands, the RGB values in the composite are slightly different than > the values in the original bands. Why is that?
Because the number of levels to be used for each component is by default 32, not 256 [0]. Markus M [0] http://grass.osgeo.org/grass70/manuals/r.composite.html > > Here's an example: > > # Import three bands > GRASS 7.0.0svn (UTM33N):~/Downloads > for b in 2 3 4; do r.in.gdal --o > input=LE71830542003069SGS00_B${b}.TIF output=b${b}; done > r.in.gdal complete. > > # Create composite > GRASS 7.0.0svn (UTM33N):~/Downloads > r.composite r=b4 g=b3 b=b2 > out=false_color --o > Creating color table for output raster map... > 100% > Writing raster map <false_color>... > 100% > r.composite complete. Raster map <false_color> created. > > GRASS 7.0.0svn (UTM33N):~/Downloads > r.info -g false_color > north=1065915 > south=856485 > east=731415 > west=497985 > > # Choose a point for testing > GRASS 7.0.0svn (UTM33N):~/Downloads > x=600000; y=900000 > > # and query with r.what > GRASS 7.0.0svn (UTM33N):~/Downloads > r.what -n map=b4,b3,b2 coord=${x},${y} > easting|northing|site_name|b4|b3|b2 > 600000|900000||67|108|96 <<============= > > GRASS 7.0.0svn (UTM33N):~/Downloads > r.what -n -r map=false_color > coord=${x},${y} > easting|northing|site_name|false_color|false_color_color > 600000|900000||12712|065:106:098 <<============ > GRASS 7.0.0svn (UTM33N):~/Downloads > > > Thanks, > Micha > > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
