Assessment of Atmospheric Correction Accuracy of Sentinel-3/Olci Images Of The Gorky Reservoir: Preliminary Results

The article examines the accuracy of atmospheric correction (AC) algorithms of Sentinel-3/OLCI images of the Gorky reservoir, whose waters are characterized by a high content of phytoplankton and dissolved organic matter. All considered algorithms showed unsatisfactory accuracy due to incorrect determination of atmospheric aerosol parameters and aerosol radiance. In pixels, where atmospheric correction algorithms overestimate the aerosol radiance, aerosol optical thickness (AOT) is 3–10 times higher than the values in the adjacent areas with more clear waters. To resolve this issue, an algorithm with a fixed AOT was proposed. The fixed AOT spectrum was determined in the area with relatively “clean water” as 5 percentile of AOT in all water pixels. The proposed algorithm allowed to retrieve remote sensing reflectance with high accuracy. The slopes of lenear regression are close to 1 and the intercepts tend to zero in nearly all spectral bands. The determination coefficients are more than 0.9; the bias, mean absolute percentage error, and root mean square error are noticeably lower than for other AC algorithms.