@article{oai:tsukuba.repo.nii.ac.jp:00051822, author = {松下, 文経 and MATSUSHITA, Bunkei and Jiang, Dalin and Setiawan, Fajar and Vundo, Augusto}, journal = {ISPRS journal of photogrammetry and remote sensing}, month = {Jun}, note = {The Secchi disk depth (ZSD) is a widely used parameter for evaluating water clarity. Here we propose an improved algorithm, which is based on a new underwater visibility theory, for retrieving more accurate ZSD from remote sensing reflectance (Rrs) in various waters. Two improvements were carried out in the new algorithm. First, we used a hybrid quasi-analytical algorithm (QAA_hybrid) instead of the sixth version of QAA (QAA_v6) for retrieving more accurate total absorption coefficient (a(λ)) and total backscattering coefficient (bb(λ)) even in turbid inland waters. Second, we used a dynamic KT/Kd ratio (i.e., ratio of diffuse attenuation coefficient of upwelling radiance and diffuse attenuation coefficient of downwelling irradiance) instead of using the fixed ratio (i.e., 1.5). The results obtained from in situ Rrs show that the improved ZSD estimation algorithm gave more accurate ZSD estimations, with the root mean square error (RMSE) reduced from 0.2 to 0.1 in log10 unit, mean absolute percentage error (MAPE) reduced from 39% to 20% (N = 178 with in situ ZSD values between 0.3 and 20.8 m). We then applied the improved ZSD estimation algorithm to the 2003–2012 MERIS images for Lake Kasumigaura to further confirm the performance of the improved ZSD estimation algorithm. The results obtained from 19 matchups demonstrate that the estimated ZSD matched well with the in situ ZSD, with the RMSE of 0.11 m and the MAPE of 15%. The improved ZSD estimation algorithm shows a potential to estimate more accurate ZSD values from remote sensing data in various waters.}, pages = {13--23}, title = {An improved algorithm for estimating the Secchi disk depth from remote sensing data based on the new underwater visibility theory}, volume = {152}, year = {2019}, yomi = {マツシタ, ブンケイ} }