Nikos A wrote: > > >> Advanced users, may I seek for some recommendation on filtering Landsat > > >> reflectance outliers?
Nikos A (replying to self): > > > (Thanks Yann) > > > Reflectance is a unit-less ratio, ranging from 0 to 1.0. So I can > > > flatten everything >1.0 to 1.0. Markus N: > > I would run r.neighbors with a 3x3 or 5x5 moving window and averaging > > or likewise. The question is always: are they outliers or data? > Wild guessing: too high to be data!? > Nikos Coming back to this! I think that Markus' suggestion was/is "correct". However, at the time of having to decide what to do, I simply flattened them. They were only a few though, not a real issue. Anyhow, just for completeness an "official" definition of reflectance, here is one copy-pasted from <http://landsat.gsfc.nasa.gov/references/glossary.html>: --%<--- reflectance - A measure of the ratio of outgoing to incoming radiation calculated by converting a radiometrically calibrated image to an innate characteristic of the target being observed. Calibrated at-satellite spectral radiance is converted to unitless reflectance by separating out the atmospheric component of the reflective band radiance and assuming that the target is a Lambertian reflector, re-radiating incident solar radiation equally in all directions. In general, reflectance is a function of incident angle of the energy, viewing angle of the sensor, spectral wavelength, and bandwidth, and the nature of the object. Also see planetary albedo, bidirectional reflectance and atmospheric correction. (Source: Dr. John Barker) --->%-- Nikos _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
