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

Abstract

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.

Acknowledgements

The Khaled bin Sultan Living Oceans Foundation and the Great Plains Seychelles are thanked for their assistance with field work and image acquisition at Alphonse Atoll.