Bathymetry, water optical properties, and benthic classification of coral reefs using hyperspectral remote sensing imagery
The complexity and heterogeneity of shallow coastal waters over small spatial scales provides a challenging environment for mapping and monitoring benthic habitats using remote sensing imagery. Additionally, changes in coral reef community structure are occurring on unprecedented temporal scales that require large-scale synoptic coverage and monitoring of coral reefs. A variety of sensors and analyses have been employed for monitoring coral reefs: this study applied a spectrum-matching and look-up-table methodology to the analysis of hyperspectral imagery of a shallow coral reef in the Bahamas. In unconstrained retrievals the retrieved bathymetry was on average within 5% of that measured acoustically, and 92% of pixels had retrieved depths within 25% of the acoustic depth. Retrieved absorption coefficients had less than 20% errors observed at blue wavelengths. The reef scale benthic classification derived by analysis of the imagery was consistent with the percent cover of specific coral reef habitat classes obtained by conventional line transects over the reef, and the inversions were robust as the results were similar when the benthic classification retrieval was constrained by measurements of bathymetry or water column optical properties. These results support the use of calibrated hyperspectral imagery for the rapid determination of bathymetry, water optical properties, and the classification of important habitat classes common to coral reefs.
KeywordsCoral reefs Remote sensing Optical properties Hyperspectral Benthic classification
This research was supported by grants from the Office of Naval Research-Environmental Optics Program as part of the Coastal Benthic Optical Properties (CoBOP) program to MPL and CDM, who also received additional ONR support for the development of the LUT methodology, and was also made possible with funding to MPL provided by the Coral Reef Targeted Research (CRTR) Program. The CRTR Program is a partnership between the Global Environmental Facility, the World Bank, the University of Queensland (Australia), the United States National Oceanic and Atmospheric Administration (NOAA), and approximately 40 research institutes and other third parties around the world. We thank Curt Davis, Robert Leathers, Valerie Downs, Dave Phinney, Emmanuel Boss, Ron Zaneveld, Charles Mazel, and the staff of the NOAA Caribbean Marine Research Center at Lee Stocking Island, Bahamas for their help and assistance. This research conforms to the applicable laws of both the United States and the Bahamas.
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