ARCSI reflectance scale

[Tomas Brunclik]

Hello all,
I tried the  ARCSI software, and got images for TOA radiance, TOA reflectance and ground reflectance. Now I suppose the radiance pixel values are directly in the radiance units W.Sr-1.M-3. But the reflectance, which is unitless ratio value of incoming/reflected light and should be theoretically within the 0-1 limits is apparently scaled or quantized. My question is how it is scaled/quantized, or what pixel value corresponds to reflectance 0 and what to reflectance 1?
Thanks in advance,
Tomas B.

[Pete Bunting [pfb]]

Hi Tomas, 

The reflectance values are multiplied by 10000 and saved as a 16bit unsigned integer - saves a lot of disk space as integers compress more efficiently than floats. The minimum value within the scene is 1 (i.e., 0.0001%) so 0 is used for no data regions. Any values which are negative (which shouldn’t happen) following the application of the 6S coefficients are assigned a value of 1, therefore if the AOT is too high you would see the visible bands only having values of 1. 

Best wishes, 

Pete

****************************************************
* Dr Pete Bunting
* Senior Lecturer in Remote Sensing
* Earth Observation and Ecosystem Dynamics Group
* Department of Geography and Earth Sciences
* Aberystwyth University
* Aberystwyth
* Ceredigion
* SY23 3DB
* UK
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