Hi, a quick look at the stats files show some differences: - "Dimensions" - "Layer Extent" - not the same range of data (from -2 to 2 in ERDAS ? oO)
so that's totally logical to get different mean and stdev ... take care to use exactly the same extent/res when you are comparing 2 files ;) cheers, Sylvain 2013/1/14 Nikos Alexandris <[email protected]> > 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 > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > >
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