[GRASS-dev] Re: [GRASS-SVN] r44252 - grass/branches/releasebranch_6_4/imagery/i.atcorr

[Yann Chemin]

>From what I can read if no file descriptor is found then do not
convert meters to km
If no file descriptor is found it should fall back to a single
altitude value found in the input parameter file, the crux is that the
value is in meters too...

A good modification would be to remove elevation (ialt) value from
parameter file and make it a separate input value to clarify the issue
value Vs raster input file. Likewise for visibility (ivis).



Yann Chemin
www.csu.edu.au

On 09/11/2010, at 4:43, Markus Neteler <neteler at osgeo.org> wrote:

> On Mon, Nov 8, 2010 at 10:28 AM,  <svn_grass at osgeo.org> wrote:
> ...
>>   grass/branches/releasebranch_6_4/imagery/i.atcorr/6s.cpp
>>   grass/branches/releasebranch_6_4/imagery/i.atcorr/main.cpp
>> Log:
>> i.atcorr: be less verbose, fix when elevation is not given
>> (merge r44250 from devbr6)
> ...
>
> Just curious about this change:
>
>> Modified: grass/branches/releasebranch_6_4/imagery/i.atcorr/main.cpp
>> ===================================================================
>> --- grass/branches/releasebranch_6_4/imagery/i.atcorr/main.cpp  2010-11-08 09:27:08 UTC (rev 44251)
>> +++ grass/branches/releasebranch_6_4/imagery/i.atcorr/main.cpp  2010-11-08 09:28:04 UTC (rev 44252)
> ...
>> @@ -331,7 +330,8 @@
>>                G_set_f_null_value(&buf[col], 1);
>>                continue;
>>            }
>> -           alt[col] /= 1000.0f; /* converting to km from input which should be in meter */
>> +           if (ialt_fd >= 0)
>> +               alt[col] /= 1000.0f; /* converting to km from input which should be in meter */
>>
>>             /* check if both maps are active and if whether any value has changed */
>>             if((ialt_fd >= 0) && (ivis_fd >= 0) && ((prev_vis != vis[col]) || (prev_alt != alt[col])))
>
> If no elevation is available, perhaps better issue a warning/fatal error?
> I am not very familiar with this code so I dunno but in general
> performing atmospheric
> correction without DEM can lead to nonsense. But perhaps my observation is
> not applicable in this code chunk.
>
> Markus
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