Harvey, M., Kobryn, H.T., Beckley, L.E., Heege, T., Hausknecht, P. and Pinnel, N. (2007) Mapping the shallow marine benthic habitats of Rottnest Island, Western Australia. In: 3rd EARSeL Workshop Remote Sensing of the Coastal Zone, 7 - 9 June, Bolzano, Italy.
The introduction of new, high resolution hyperspectral sensors has led to growing interest in the development of techniques to utilise data from these instruments for mapping the shallow marine environment. The increased spectral resolution of the hyperspectral sensors allows the use of the unique spectral signatures of the individual habitat components to identify these components within the image. Hyperspectral data also allows for the mapping of habitats in shallow areas that are inaccessible to other methods such as hydro-acoustic mapping. The coastal waters surrounding Rottnest Island, Western Australia, provide a unique opportunity to apply hyperspectral imaging techniques in a temperate environment because of the oligotrophic conditions maintained by the Leeuwin Current. The shallow marine benthic habitats of Rottnest Island Reserve have been mapped to a depth of ~15 m, using spectral signatures contained in a library created from in-situ measurements of the dominant habitat components. Three lines of HyMap hyperspectral data flown for the Rottnest Island Reserve in April 2004 were corrected for sunglint, atmospheric effects and the influence of the water column using the Modular Inversion and Processing System which requires no inputs from parameters measured in the field. A decision tree based classification scheme which utilises a range of spectral similarity measures was used to map the different habitat components identified in the bottom reflectance image and the results were validated in the field using SCUBA divers. The shallow subtidal habitats found around Rottnest Island are generally dominated by either bare sand, reef with large macroalgae, such as Ecklonia radiata and Sargas-sum spp., or a number of different seagrass species. These new hyperspectral imaging techniques provide a platform for the mapping of shallow marine benthic habitats over a broad area, at a scale that is relevant to marine planners and managers.