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Evaluating Sentinel-2A atmospherically corrected reflectance using the 6SV model

In this study, the Bottom-Of-Atmosphere (BOA) reflectance over Egbert, Ontario, Canada on September 24, 2016, as obtained by the Sentinel-2A Multi-Spectral Imager and corrected by the Sentinel-2 atmospheric Correction (Sen2Cor) software, was evaluated based on the 6SV atmospherically corrected reflectance. The aerosol and water vapor parameters used in the 6SV model were obtained from the AERONET data. The evaluation results showed that for the visible bands, the Sen2Cor BOA reflectance was lower than the 6SV BOA reflectance, with a maximum relative bias of −36.5%, due to an overestimation of the aerosol optical depth retrieved by Sen2Cor. The bias of the BOA reflectance could also affect the vegetation index (VI) calculation. Four VIs were calculated and compared using the different BOA reflectance. The maximum relative bias was 18.2%. The study shows that the BOA reflectance corrected by Sen2Cor should be treated with some degree of caution, especially for the visible bands and VIs.