On Mon, May 2, 2016 at 8:28 PM, Manamana <joanna.mar...@wp.pl> wrote: > I have a problem with i.topo.corr > Data: > Landsat 7 ETM+ WGS 84/zone38N > SRTM 3arc WGS84 > What I did: I did the atmospheric correction of landsat bands with dos1 I > did the illumination model for SRTM, in a different location and mapset > since it is in a different coordinate system and then I used r.proj to > import the illumination model to the mapset with my landsat data. But! When > I run i.topo.corr the results are not as they should be. The output map is > in dark grey, almost black, just one colour. I thought that maybe it is > because the resolution of SRTM is different than resolution of Landsat.
... this is possible. My suggestion: Instead of processing SRTM in a different location, import it right away into the UTM38N location of your Landsat data through reprojecting on the fly with bilinear resampling. Extra hint: Avoid SRTM 3arc but use the newest 1 arc-second for global coverage (~30 meters). You get it from EarthExplorer (http://earthexplorer.usgs.gov/) which can be used to search, preview, and download Shuttle Radar Topography Mission (SRTM) 1 Arc-Second Global data. The collections are located under the Digital Elevation category. [1] GRASS 7.1.svn (nc_spm_08_grass7):~ > # set computational region to e.g. Landsat channel 3: g.region raster=lsat7_2000_30 -p # Import with reprojection on the fly. Recommended parameters: # resample Resampling method to use for reprojection - bilinear # extent Output raster map extent # - region: extent of current region # resolution Resolution of output raster map # - region: current region resolution - limit to g.region setting from above r.import input=n35_w079_1arc_v3.tif output=srtmv3_resamp resample=bilinear \ extent=region resolution=region title="SRTM V3 resampled to Landsat7 resolution" # beautify colors: r.colors srtmv3_resamp color=elevation Keep in mind that SRTM is space borne. I have now added a similar example to the r.import manual page (will show up online in a few days) and also some Wiki pages. Hope this helps, Markus [1] Pro tip: Power users who know the tile name may grab it directly from this web server (avoid to look at the entire directory in a Web browser, it may overload it since the page is huge! eg North Carolina tile (note that it is in HGT format rather that GeoTIFF as obtained from EarthExplorer): http://e4ftl01.cr.usgs.gov/SRTM/SRTMGL1.003/2000.02.11/N35W079.SRTMGL1.2.jpg http://e4ftl01.cr.usgs.gov/SRTM/SRTMGL1.003/2000.02.11/N35W079.SRTMGL1.hgt.zip http://e4ftl01.cr.usgs.gov/SRTM/SRTMGL1.003/2000.02.11/N35W079.SRTMGL1.hgt.zip.xml _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
