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I'm having some peculiar issues with Sentinel 2 data. I've downloaded two coterminous tiles (one L1C tile from EarthExplorer and one L1C/L2A tile from AWS) taken at the same time and date. I have done this to verify that my methods of atmospheric correction (ESA's sen2cor tool) are valid and give me precisely what I would get from simply downloading AWS' L2A product. The tile ID follows: S2B_MSIL1C_20190113T181719_N0207_R084_T12TWR_20190113T200650

The issue is, it doesn't produce identical results. When I go to calculate NDVI from my bottom-of-atmosphere product, I get different values when using AWS' L2A versus the L2A I produced using sen2cor.

I've done a little research on this and found reference to a "pilot" introduced to ESA's L2A_GIPP process in 2018. There seems to be a version 2.11 floating around out there, while the process in sen2cor (2.07) produces "L2Ap" instead of "L2A"

My question is: Does anyone know why an identical atmospheric processing chain would produce dissimilar results?

  • Still tracking this issue down and found this: forum.step.esa.int/t/… Apparently ESA uses a proprietary DEM in their in-house correction process, which could lead to the slight variation I'm seeing. Not yet 100% convinced this is the main issue, but for anyone researching this down the road, it is noteworthy. – instructorjack Jan 31 at 21:19
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ESA is using Sen2Cor 02.08 for processing, while currently available version is 02.05.05. According to the Copernicus EO Support, "the release of v.02.08.00 is planned at the end of week 6 (8th of February), pending a successful validation on their side".

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