On Wednesday 12 of June 2013 02:05:48 Huub Munstege wrote: > Hi there all! Greetings from a happy Grass-root GISser on an Archlinux > box...
Hi! > Is there already a way to analyze the new Landsat 8 images (they are already > available!)? In grass64 you would want to use i.landsat.toar first (with one of the correction methods) which supports the new Landsat_8 OLI/TIRS sensor(s). > We are in particularly interested in the Normalized > Standardized Vegetation Index (NDVI). Having (top-of-canopy) reflectances is, if I am not wrong, a *must* in order to get the desired ration that reflects the status of the vegetation. You are, I guess, probably interested in the "i.vi" module (with "viname=ndvi"). > We noticed a shift in wavelength > range that is best depicted here: > http://www.gisagmaps.com/landsat-8-about-refinements/ Interesting, they "narrowed" the band. They probably know what they are doing. New stuff to explore :D > Doing the well-known raster map calculation with the bands 5 (NIR) and 4 (R) > of L-8 doesn't give a satisfying result. Very bluntly we subtracted 0.12 > from the 'ndvi' raster derived from L-8. Why subtract? Precisely, if I may ask, did you "threshold" it? Cut-off anything below? > Without doubr there must be more > elegant and correct solutions. Any ideas are very welcome Would you mind to elaborate a bit more? Thanks, Nikos _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
