UNDERWATER SPECTROSCOPY: METHODS AND APPLICATIONS IN A CORAL REEF ENVIRONMENT

摘要

Rising concern over the declining health of coral reef communities has prompted significant interest in applications of remote sensing toward the monitoring and assessment of these ecosystems. In that regard, hyperspectral imaging systems such as NASA's Airborne Visible InfraRed Imaging Spectrometer (AVIRIS) provide promising results for the utility of such sensors to examine benthic habitats in this complex marine environment. The spectral resolution of hyperspectral instruments is not only an advantage for discriminating between different habitat types, but also for resolving the confounding effects contributed by the overlying water column and its constituents. In accordance with the associated analysis methods, a demand has arisen to establish field methods in underwater spectroscopy as support for processing hyperspectral imagery. Discussed here are the methods and results obtained using a GER 1500 field portable spectroradiometer in a custom underwater housing to obtain reflectance measurements in both control experiments and under field conditions. As a focus for these experiments, different lighting conditions were employed to establish the reliability of field spectra obtained under variable situations. Experiments were first performed in a controlled pool environment at the UC Davis Bodega Marine Laboratory, followed by a series of field measurements in Kaneohe Bay, Oahu, Hawaii. Conclusions address the utility of the resulting reflectance measurements for processing AVIRIS imagery acquired over Kaneohe Bay.