[GRASS-user] Using i.atcorr on SPOT4 and SPOT5 imagery

[Daniel Victoria]

>From what I recall, i.atcorr was based off a fortran code writen by
someone at INPE. That original Fortran program expects the input
images to be 8 bit and produces another 8bit image as a result. I
believe that's why the grass i.atcorr has both the iscl and oscl
options.

In my opinion, these input and output scaling parameters confuses
things a little. I'm not sure how the command works internally and if
these parameters are needed but, I have a feeling they are necessary
if we work with images with more than 8 bits.

Cheers
Daniel

On Tue, Jul 17, 2012 at 7:12 PM, Markus Neteler <neteler at osgeo.org> wrote:
> Hi Cody,
>
> On Thu, Jul 5, 2012 at 8:27 PM, Cody Schank <codyschank at gmail.com> wrote:
> ..
>> One other thing.  For the input range, is it necessary to put the actual
>> range of the input radiance values (range usually about 0 to 150).  If I
>> leave it as 0,255 I get different output values.  Just want to clarifiy the
>> significance of that input field.
>
> You mean:
>
> iscl=min,max
>     Input imagery range [0,255]
>     Default: 0,255
>
> Honestly I don't know - In the source code I see:
>
>     struct Option *iscl;    /* input data is scaled to this range */
>
> Perhaps internally the command wants to see the image scaled to 8bit?
> Anyone having an idea?
>
> Markus
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