Estimation of Colored Dissolved Organic Matter From Landsat-8 Imagery for Complex Inland Water: Case Study of Lake Huron

Spectral reflectance data, including irradiance reflectance (R
_t
) and remote sensing reflectance (R
_rs
, sr
^-1
), and colored dissolved organic matter (CDOM) absorption coefficients a
_CDOM
(440), were collected in the Saginaw River and Kawkawlin River plume regions of Lake Huron. We developed an empirical band ratio algorithm to derive a
_CDOM
(440) that could be directly applicable to Landsat-8 imagery. A model ranking method is used to determine the best band ratios as well as their empirical functions. One problem of previous CDOM estimations from Landsat imagery is that they usually use R
_t
or R
_t
/π rather than the real R
_rs
as the input data, but as a result of our study, algorithms derived using R
_rs
performed much better than using Rt. The green/red band ratio gave the best accuracies by fitting with power and exponential models (power model: R
²
= 0.819 and RMSE = 0.889 m
^-1
and exponential model: R
²
= 0.829 and RMSE = 0.863 m
^-1
). The power and exponential models were further validated using an independent data group, achieving excellent results with the RMSE of 0.642 and 0.504 m
^-1
, respectively. The application of the exponential model a
_CDOM
(440) = 40.75e
^-2.463x
, x = R
_rs
(B3)/R
_rs
(B4) on two Landsat-8 images demonstrated that estimating CDOM from to Landsat-8 imagery has potential applications for monitoring water quality in long term and large scale.