Gökçen Güner: > > This will not be a specific GRASS question. My friend and I tried to > > calculate NDVIs of same data set and results seem same to us.
What kind of images are those, if I may ask? Which sensor? > > But checking statistics of each output we saw that statistics are very > > different. I mean, median, mean, std.dev values of Grass output and Erdas > > output are different. > > We couldn't find an explanation for this situation. What can be > > the reason for this? > There are reasons. For example, different pixel inclusion rules (of course I > have in mind border-near pixels). Other reasons might be the spatial > resolution and extent (remember, GRASS-GIS is strict with that) and the > presence of a MASK. Also, what about NULL or NoData cells? How does ERDAS deal with them -- I don't remember now. How are they defined, if they exist, in your image? What does "r.describe -r" return for the data set(s) in question? Thanks, Nikos
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