HYPERSPECTRAL DISCRIMINATION AND SEPARABILITY ANALYSIS OF CORAL REEF COMMUNITIES IN REDANG ISLAND

Abstract

An assessment ofthe spectral separability between different reefspecies was undertaken using underwater hyperspectral measurements. In-situ upwelling and downwelling radiances were collected for eight substrates of Redang Island reef communities, including five corals, algae and sediments. Underwater spectral measurements ranging from 350 to 800 nm were taken 0.25 m above the substrate using a Satlantic HyperOCR spectroradiometer. Hyperspectral retlectance and derivative datasets were analysed using the stepwise discriminant function analysis to determine the best discriminating wavelength for each species at Chagar Hutang, Redang Island. Results showed that major reflectance features of reef species were identified by two distinctive peaks at 575 and 610 nm. Stepwise wavelength selection revealed that reefspecies could be well-distinguished using the derivative dataset (15 non-contiguous wavelengths) compared to hyperspectral reflectance (4 non-contiguous wavelengths). These preliminary results are encouraging and demonstrated the possibility to spectrally distinguish different types of coral reef community using hyperspectral remote sensing.