Hi, For a project I am involved with, we are conducting landcover classification from LANDSAT TM (orthorectified) data downloaded from GLCF. We are now in the process on pre-processing the image and then conduct classification using i.smap.
Following the GRASS book, we will be conducting the pre-processing steps outlined: 1. calibration from DN to apparent radiance at sensor - gain/bias offsets following grass book 2nd ed. (page 222) r.mapcalc "band.rad = ((LMAX - (LMIN))/(255.0 - 1.0)) * (band -1.0) + (LMIN)" or i.landsat.toar 2. correction for atmospheric effects use i.atcorr problem: the metadata supplied by GLCF does not indicate image acquisition time sample metadata: http://tinyurl.com/6oo428 or use i.landsat.dehaze 3. correction for topographic/terrain effects (most of my study area are in maountainous regions) use book 2nd ed. (page 226) "cosine correction" using r.sunmask, r.mapcalc Problem: again, no image acquisition time 4. removal of clouds use i.landsat.acca https://svn.osgeo.org/grass/grass-addons/imagery/i.landsat.acca/ The beauty with GRASS and the GRASS book is that it has the tools/modules I need for this project, however, I find it difficult to choose which one I should use (i.atcoor or i.landsat.dahaze?). Am I following the steps in correct order? Or is it necessary to do all this? Reading from GLCF documentation, they did orthrectification for this image already. Any pointers would be very helpful. cheers, maning -- |---------|----------------------------------------------------------| | __.-._ |"Ohhh. Great warrior. Wars not make one great." -Yoda | | '-._"7' |"Freedom is still the most radical idea of all" -N.Branden| | /'.-c |Linux registered user #402901, http://counter.li.org/ | | | /T |http://esambale.wikispaces.com| | _)_/LI |---------|----------------------------------------------------------| _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user