[postgis-users] NDVI Calculation from two bands within one Raster

[Nordgren, Bryce L -FS]

'WHEN (rast1 + rast2 = 0) THEN XXX ELSE (rast1 - rast2) /(rast1 + rast2)::float END'

> Returned "Neither raster provided has a NODATA value for the specified band
> indices.  NODATA value set to minimum possible for 8BUI"

Ummm,

NDVI is calculated on reflectance values in these bands, not raw DN. Your inputs should already be floating point values, and they should never be less than 0.0 or greater than 1.0. The big concern here is that each band is likely to have a different relationship between DN and reflectance, making the above equation produce something...unexpected.




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