[GRASS-user] implementing frost filter in grass
Hi, I'm trying to implement the FROST [0] SAR despeckling filter in a GRASS script. The code according to the referenced link is below: # The implementation of this filter consists of defining a circularly symmetric filter with a set of weighting values M for each pixel: M = exp(- A * T) where: A = DAMP * (V / I**2) T is the absolute value of the pixel distance from the centre pixel to its neighbours in the filter window DAMPis the exponential damping factor V is the variance of the grey-level in the filter window I**2is the square of the mean grey level in the filter window The resulting grey-level value R for the smoothed pixel is: R = (P1*M1 + P2*M2 + ... + Pn*Mn) / (M1 + M2 + ... + Mn) where: P1 .. Pn are grey levels of each pixel in filter window M1 .. Mn are weights (as defined above) for each pixel # Computing for A is straightforward using r.mapcalc. I'm having difficulty in deriving T which was defined as the absolute value of the pixel distance from the centre pixel to its neighbours in the filter window I investigated r.cost and r.distance but it is not suited for a moving window operation (perhaps I'm wrong). It maybe possible r.mapcalc's row-column offset but it will loose the ability to interactively define a window size. Any tips on how to get the T and final R values? Advance thanks! [0] http://web.archive.org/web/20071216081728/http://www.pcigeomatics.com/cgi-bin/pcihlp/FFROST -- cheers, maning -- Freedom is still the most radical idea of all -N.Branden wiki: http://esambale.wikispaces.com/ blog: http://epsg4253.wordpress.com/ -- ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Geotiff files
Hi, I'm new to Grass and to Raster files, and although I know some concepts, I'm having trouble to work with geotiff files. Basically, I want to import tiff files downloaded from http://nassgeodata.gmu.edu/CropScape/into vector layers. Any ideas on how can I do that? Thanks, Pedro PS - I'm using the GUI ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
