iCOR -S2 - understanding the pixel values

Hello all,

I have used iCOR for Sentinel-2 in SNAP. I did the following steps

  1. Download S2 MSIL1C image
  2. Go to iCOR - S2 in SNAP, give the MTD_MSIL1C.xml as source product
  3. Under the parameter settings - leave everything to default and run

The _10m, _20m and _60m output images are generated. The pixel values of these bands are very different from that of the original - the value range is between Min = -0.005, Max = 1.057 for the Blue band in the processed _10m image. The original blue band has Min = 869, Max = 1872.

Why is there this difference between the values before and after running iCOR on the image?

Thank you!

the original values seem to be in DN, i.e. reflectance expressed as unsigned integers. For getting reflectances, divide them by the QUANTIFICATION_VALUE, usually 10000.
iCor output is directly in reflectances. they will be different from the original reflectances as iCor output is bottom-of-atmosphere reflectances, original values are top-of-atmosphere reflectances.

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Thats perfect! Thanks very much!