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please help with ndvi calculation [message #52835]

Thu, 01 March 2007 21:09

beardown911
Messages: 21
Registered: March 2007

Junior Member

Hello all,

I am new in idl programming, and have been trying to figure out to
write a simple code to calculate ndvi.

Here is what I've done, but gave weird value.
------------------------------------------------------
pro ndvi
image = read_tiff ('/rsi/idl62/training/data/image.tif')
help, image

sub = float(image[0,*,*]-image[1,*,*])
sum = float(image[0,*,*]+image[1,*,*])

ndvi_image = sub / sum

write_tiff, '/rsi/idl62/training/data/ndvi_test.tif', ndvi_image
end
-------------------------------------------------------
The image.tif have three bands(nir, red, green) 8 bit image.
The resulting ndvi image is still integer and values are totally
wrong.
Could anybody help me to fix this?

Thank you,
Phil

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