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Rescaling byte (0-200) ndvi to -1 to 1 values [message #80869]

Thu, 19 July 2012 11:18

Narnia
Messages: 5
Registered: July 2012

Junior Member

I'm using the eMODIS 10-day product from the USGS with this description: "MODIS NDVI data are stretched (mapped) linearly (to byte values) as follows:
[-1.0, 1.0] -> [0, 200]
Invalid Values: 201 - 255

NDVI = (value – 100) / 100; example: [ (150 – 100) / 100 = 0.5 NDVI ]"

I am trying thus to scale the data in ENVI just using Band Math [expression:((b1-100)/100)] and all the values I get are 0 across my entire image. Any thoughts as to why?

Secondly, I need to do this for over 400 images; can someone suggest a quick script that can read and scale this data in IDL? I tried 'ScaledImage' but i keep getting errors as well...

Thank you so much!

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