The Level-2A operational processor generates, from algorithms of scene classification and atmospheric correction, Level-2A atmospherically corrected Surface Reflectance (SR) products from Level-1C products.
From the mid-March 2018, the Level-2A became an operational product, beginning with coverage of the Euro-Mediterranean region. Global coverage started in December 2018.
Level-2A can also be generated by the User from the Level-1C product using the SENTINEL-2 Toolbox or the standalone version of the Sen2Cor processor.
Please note that starting with the PB 04.00 (25th January 2022), the dynamic range of the Level-2A products is shifted by a band-dependent constant: BOA_ADD_OFFSET. This offset will allow encoding negative surface reflectances that may occur over very dark surfaces. From the user’s point of view, the L2A Surface Reflectance (L2A_SR) shall be retrieved from the output radiometry as follows:
- Digital Number DN=0 remains the “NO_DATA” value
- For a given DN in [1; 1;215-1], the L2A SR reflectance value will be:
L2A_SRi = (L2A_DNi + BOA_ADD_OFFSETi) / QUANTIFICATION_VALUEi
The radiometric offset value is reported in a new field in the General_Info/Product_Image_Characteristics section of the Datastrip and User Product Metadata. It is initially set to -1000 Digital counts for all bands.