On Thu, Jun 20, 2013 at 6:24 PM, Nikos Alexandris <n...@nikosalexandris.net> wrote: > Markus Metz wrote: > >> I think I figured it out: > >> The EVI formula in i.vi is for MODIS. > > That's precise, EVI is MODIS specific. We should clearly describe this in the > manual (I will try to alter the respective text).
>From the literature, I gor the impression that EVI can be calculated from other sensors as well, as long as you get the coefficients right. > > >> The generic formula is >> >> G * ( nir - red) / (nir + C1 * red - C2 * blue + L) > >> where G is a gain factor, C1, C2 are coefficients to correct for >> aerosol influences in the red band using the blue band and L is the >> canopy background adjustment that addresses non-linear, differential >> NIR and red radiant transfer through a canopy. > Assuming that the input to i.vi should be properly preprocessed bands with a theoretically maximum range of [0, 1], you could set L to 0.0001 and would get reasonable EVI values, sensor-independent. Markus M _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev
