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Live Coral Cover Index Testing and Application with Hyperspectral Airborne Image Data
Research Institute for the Environment and Livelihoods, Charles Darwin University, Casuarina Campus, Darwin, NT 0810, Australia
Centre for Spatial Environmental Research, School of Geography, Planning, and Environmental Management, University of Queensland, St Lucia, QLD 4072, Australia
* Author to whom correspondence should be addressed.
Received: 8 October 2013; in revised form: 13 November 2013 / Accepted: 18 November 2013 / Published: 20 November 2013
Abstract: Coral reefs are complex, heterogeneous environments where it is common for the features of interest to be smaller than the spatial dimensions of imaging sensors. While the coverage of live coral at any point in time is a critical environmental management issue, image pixels may represent mixed proportions of coverage. In order to address this, we describe the development, application, and testing of a spectral index for mapping live coral cover using CASI-2 airborne hyperspectral high spatial resolution imagery of Heron Reef, Australia. Field surveys were conducted in areas of varying depth to quantify live coral cover. Image statistics were extracted from co-registered imagery in the form of reflectance, derivatives, and band ratios. Each of the spectral transforms was assessed for their correlation with live coral cover, determining that the second derivative around 564 nm was the most sensitive to live coral cover variations(r2 = 0.63). Extensive field survey was used to transform relative to absolute coral cover, which was then applied to produce a live coral cover map of Heron Reef. We present the live coral cover index as a simple and viable means to estimate the amount of live coral over potentially thousands of km2 and in clear-water reefs.
Keywords: live coral; spectral index; band ratios; image processing; hyperspectral; field survey; remote sensing; CASI
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Joyce, K.E.; Phinn, S.R.; Roelfsema, C.M. Live Coral Cover Index Testing and Application with Hyperspectral Airborne Image Data. Remote Sens. 2013, 5, 6116-6137.
Joyce KE, Phinn SR, Roelfsema CM. Live Coral Cover Index Testing and Application with Hyperspectral Airborne Image Data. Remote Sensing. 2013; 5(11):6116-6137.
Joyce, Karen E.; Phinn, Stuart R.; Roelfsema, Chris M. 2013. "Live Coral Cover Index Testing and Application with Hyperspectral Airborne Image Data." Remote Sens. 5, no. 11: 6116-6137.