Can enhanced vegetation index have values greater than 1? I am using the ENVI software to calculate enhanced vegetation index (EVI) of a hyperspectral image and my EVI value range was from 0 to 1.9. Is it wrong?
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1 Answer
Based on documentation from ENVI software the values should be between -1 and 1, see here
The Enhanced Vegetation Index (EVI) is an algebraic equation of:
EVI = G X ((NIR - RED)/ (NIR + (C1 x RED)-(C2 x BLUE) + L))
Where NIR is the value of the near infrared band, RED is the value of the red band, BLUE is the value of the blue band, (all three bands are atmospherically-corrected), L is the canopy background adjustment. Additionally G is the gain factor, C1 and C2 are the coefficients of the aerosol resistance term. In ENVI software G = 2.5, C1 = 6, C2 = 7.5, and L = 1.
For more background information on EVI go to the Wikipedia page here or for a thread on how to implement the equation manually go here.
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Thank you James for your answer. I apply the same equation to my EVI and get the result as in my question. I have read from ENVI forums that range -1 to 1 may not applied ti EVI. Here i share with you the link exelisvis.com/Support/Forums/tabid/184/forumid/6/postid/16689/…, Thanks again Commented Sep 11, 2015 at 6:48
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1This is not my area of expertise but which type of hyperspectral image are you using? You may need to apply a scale factor. If you read to the bottom of the thread on this link. They talk about applying a scale factor of 0.0001 to the raster bands. Additionally make sure that your bands are applying floating point math rather than integer as it says on the thread you sent as well as the one I list above.– GeoSharpCommented Sep 11, 2015 at 6:57