An evaluation of waveband pairs for water column correction using band ratio methods for seabed mapping in the Seychelles

The differential attenuation of visible light (wavelength 400-700 nm) as it travels through the water column confounds the interpretation of remotely sensed imagery acquired over the sea floor. This can be addressed using depth-invariant processing techniques that ratio the radiance values of two wavebands. An evaluation of the performance of different waveband pairs for creating depth-invariant indices of the sea floor is presented. Twenty-eight different band pairs extracted from multispectral Compact Airborne Spectrographic Imager (CASI) data are assessed for the creation of depth-invariant indices over the reef profile of Alphonse Atoll in the Seychelles (water depth 0-30 m). Findings indicate that, for optimal performance, bands selected for depth-invariant processing must be at least 90 nm apart to achieve an optimal ratio of attenuation coefficients within the water column. This optimal ratio must also lie at a central point of the visible spectrum at which longer wavelength bands are not fully attenuated, while shorter wavelength bands exhibit some attenuation over a depth range that coincides with the features of interest in the water column.