On Monday 14 of January 2013 01:03:42 Gökçen Güner wrote: > Hi, Hi!
> 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. 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. How different? Can you please post exact numbers if that is ok? If differences are minor, you can simply ignore them :-) > 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. The experts might give better clues. Best, Nikos > PS: > For NDVI, we used this formula: (NIR_Band - RED_Band) / (NIR_Band + > RED_Band) Note, grass7 has i.vi for this job :-)
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