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Apparent reflectance function NDVI issue

Question asked by johannes.botha_ACTGOV on Jan 13, 2019
Latest reply on Jan 13, 2019 by Dan_Patterson

I'm using ArcGIS Pro 2.2 and ArcGIS 10.6.  I used the apparent reflectance function on SPOT 7 imagery (ortho product) and the values were expressed as integers (e.g. scale factor 50000, scale offset 5000).  When making an NDVI using the corrected imagery, the maximum NDVI values for the scene are 0.62, which is much lower than expected. 

However, when the apparent reflectance values were expressed using the albedo button (floating point e.g. 0 - 1) in the Apparent reflectance function window, the maximum NDVI values jumped to 0.83.

What is the issue here?  Am I missing something? 

 

Also, am I correct in assuming the Apparent Reflection function only corrects to top-of-atmosphere?

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