[GRASS-user] low radiance values after i.atcor and i.topo.corr

[Markus Neteler]

On Mon, Jun 16, 2008 at 11:59 AM, maning sambale
<emmanuel.sambale at gmail.com> wrote:
> After implementing gain and bias correction and topographic
> correction, I get very low values for landsat data data
> for example range of values of band1:
>
> GRASS 6.3.1svn (p112r056):~ > r.info lsat7_2000.toar.1 -r
> min=0.030303
> max=0.372067
...
> Running these range of values to an i.cluster reports very low separability:

As far as I see it is related to the fact that i.cluster reads in as
integer (CELL)
through G_get_c_raster_row():
 http://download.osgeo.org/grass/grass6_progman/gis_2get__row_8c.html
...
> I assume this is due to the very low range of values (0.0xxx) of the
> input images.  Running r.rescale.eq to "stretch" the range of values
> doesn't also help.

You may try to multiply the values with 100 or 1000 using r.mapcalc.

Please let us know how it works.

Markus