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How can I calibrate Sentinel-2 products, to extract the reflectance?

I've downloaded few Sentinel-2 products from https://scihub.copernicus.eu/s2/#/home, and opened them with SNAP but its radiometric calibration is dedicated only to SAR products.

On ENVI, the Radiometric calibration tool is seemingly only capable of extracting the radiance. What is the difference between the radiance and the reflectance? Is the estimation of the radiance counted as a radiometric calibration of a product?

  • Not entirely familiar with the sensor, other than an msi bird similar to landsat. If that's the case, its odd that it would load by default in radiance. Youre just doing classifications? Should plot you spectra in reflectance, and should be able to use that tool to do so. What is the textual result/error ? Algorithms ( regarding atmospheric correction, etc) – geodranic Dec 9 '15 at 1:59
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Sentinel-2 Level 1C data are expressed in reflectance with a scaling factor, not in radiance. You have to divide by 10000 to get the reflectance. In the preliminary products shown this autumn, you had to divide by 1000.

The scaling factor is given in the xml file at the root of the product directory.

<QUANTIFICATION_VALUE unit="none">10000</QUANTIFICATION_VALUE>

There is no offset and the no_data value is 0.

  • Can you tell me how the TOA reflectance is defined? I can't find the definition in any official document. – Generic Wevers May 12 '16 at 8:15
  • rho=(pi.L)/(Es cos theta_s) where L is TOA radiance, rho is TOA reflectance, Es is the sun irradiance, theta_s is the sun zenith angle, and pi.. is pi. – O. Hagolle May 15 '16 at 7:57
  • The sun irradiance Es must account for the Earth Sun distance variations – O. Hagolle May 21 '16 at 15:54
  • @O.Hagolle Is there a scaling factor for images from june 2016? I am unable to find this quantification value in the xml file and was hence wondering. – tg110 Sep 13 '16 at 14:12
  • I am not aware of that. There are several xml files in a product, are you using the product xml or the granule xml ? It is in the product xml, with a name like that : S2A_OPER_MTD_SAFL1C_PDMC_20160727T183119_R008_V20160727T104250_20160727T104250.xml: – O. Hagolle Sep 13 '16 at 20:36

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