Establishing a global algorithm for water quality mapping from multi-dates images Optical model of water A physical model relating radiance from the water column and the concentrations of the water quality constituents provides the most effective way of analyzing remotely sensed data for water quality studies. Reflectance is particularly dependent on inherent optical properties: the absorption coefficient and the backscattering coefficient. The irradiance reflectance just below the water surface, R(l), is given by Kirk (1984) as where l = the spectral wavelength b = the backscattering coefficient a = the absorption coefficient The inherent optical properties are determined by the contents of the water. The contributions of the individual components to the overall properties are strictly additive (Gallegos and Correl, 1990). For a case involving two water quality components, i.e. chlorophyll, C, and suspended sediment, P, the simultaneous equations for the two channels given by Gallie and Murtha (1992) can be expressed as 
where bbw(i) = backscattering coefficient of water bbc* = specific backscattering coefficients of chlorophyll bbp = specific backscattering coefficients of sediment aw(i) = absorption coefficient of water ac* = specific absorption coefficients of chlorophyll ap* = specific absorption coefficients of sediment C = chlorophyll P = suspended sediment Regression Algorithm TSS concentration can be obtained by solving the two simultaneous equations to get the series of terms R1 and R2 that is given as 
where aj, j = 0, 1, 2, … are the coefficient for equation (3) that can be solved empirically using multiple regression analysis. This equation can also be extended to the three-band method given as 
where the coefficient ej, j = 0, 1, 2, … can also be solve empirically. |