Apparent reflectance function NDVI issue

[JohannesBotha]

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?

[DanPatterson_Retired]

Apparent Reflectance function—ArcGIS Pro | ArcGIS Desktop 

Spot 7 isn't on the list... and other information, in case you haven't seen it

[JohannesBotha]

Arcgis reads the SPOT 7 DIMAP info correctly, though (and SPOT 6/7 should have exactly the same parameters anyway), and displays the correct gain/bias in the Ap Ref function window.

[DanPatterson_Retired]

I will flag the help if that is the case... but I usually wait unitl 'should' becomes 'does'

[JohannesBotha]

Good point.

[Anonymous User]

Dear Sir.

Hello,

Please i need your help about images Spot-6/7,and ArcGisPro 

can i get your Email,to communicate.

thanks

Mohsine1818@hotmail.com

Cordialy

[JohannesBotha]

To add to my confusion about this issue, when I convert the individual floating point "albedo" rasters to integers via the raster calculator (instead of taking that option in the apparent reflectance function window), the resulting NDVI also gives me the higher, "correct" answer.

[DanPatterson_Retired]

I will defer to the RS types to leap in at this point.

good luck