Hi, On Wed, Nov 13, 2019 at 2:18 PM Markus Metz <[email protected]> wrote: > On Wed, Nov 13, 2019 at 12:59 PM Veronica Andreo <[email protected]> wrote: > > > > Hi all, > > > > I'm using i.atcorr for atmospheric correction of Pleiades imagery. The data > > comes as DN in 12 bits. > > That is, values can be in the range 0, 4095, but the full possible range is > not necessarily used. > > > Reading the manual of i.atcorr, I get that I must provide radiance data. > > Hence I converted each band to radiance using gain and bias from the > > metadata. Now, for the range parameter in i.atcorr, I assume I must pass > > the min/max output of r.info for each band. There's no extra info in the > > metadata about theoretical range for each band. > > No, the range parameter in i.atcorr needs the theoretical range.
Since it isn't that obvious yet I'd suggest to reword the description at https://github.com/OSGeo/grass/blob/master/imagery/i.atcorr/main.cpp#L496 from: opts.iscl->description = _("Input range"); to something like: opts.iscl->description = _("Input range (theoretical range)"); (feel free to submit a PR) > For example for Landsat, values can be in the range 1, 255 (0 is reserved for > nodata IIRC), but actual band values usually cover only a part of that range. > Therefore min/max of a band is not correct. This valuable hint might to into the manual. best markusN > Regarding Pleiades or other imagery, you need to get from documentation or > metadata the valid range and use this as range for i.atcorr. > > HTH, > > Markus M > > > > > In the i.atcorr manual and in some older emails, I read for example, that > > the range for Sentinel 2 is 1 to 10000. However here [1] it says: > > "Per-pixel radiometric measurements are provided in Top Of Atmosphere (TOA) > > reflectances along with the parameters to transform them into radiances". > > AFAIU, 1,10000 is TOA range. > > > > So, I'm a bit lost... What is really this range parameter representing? > > > > Thanks much in advance > > > > Vero > > > > [1] > > https://earth.esa.int/web/sentinel/user-guides/sentinel-2-msi/product-types/level-1c > > _______________________________________________ > > grass-user mailing list > > [email protected] > > https://lists.osgeo.org/mailman/listinfo/grass-user > _______________________________________________ > grass-user mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/grass-user -- Markus Neteler, PhD https://www.mundialis.de - free data with free software https://grass.osgeo.org https://courses.neteler.org/blog _______________________________________________ grass-user mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/grass-user
