PVI processing - export of reflectance values - Sentinel 2 L2A

Hi all,

Would you please help me with one topic?
I’d like to perform calculation of PVI index (via processor in Land Thematic Processing) of the blueberry farm.
This index requires value of the angle between NIR reflectance and the soil line (like on the chart attached).

(source: http://web.pdx.edu/~nauna/resources/8-2012_lecture1-vegetationindicies.pdf)

To find that angle I found an area on the field with grass only, no blueberries. I draw the polygon and exported mask pixels ‘geometry’ to txt file, and opened the file in Excel. In Excel I created the scattered plot (B4 values on horizontal axis, B8 values on vertical axis) and the linear trend line.

The problem is that the value of the angle is more than 90 degrees, so my soil trend line is pointed slightly down.

My question is: are the steps described above are correct? Are the values exported into Excel are reflectance values or just digital numbers? If latter, how can I export reflectance values or specify the value of the angle in other way?

I use L2A Sentinel 2 products, SNAP 5.0.

Thank you for your help in advance.
Have a nice day, Wojciech


You can take a look at this post, maybe it helps you a bit.
The values produced by the PVI processor should be reflectance (float) values, not DNs (integers).