Measuring and modeling water column effects on hyperspectral reflectance in a coral reef environment

Abstract

Much attention has been given to hyperspectral remote sensing of benthic habitat recently to quantify spectral signatures, examine linear mixing, map geomorphic zonation, or identify temporal change with varying degrees of confidence and success. Relatively less attention has been given to the effects of the water column on the hyperspectral signal given various water depths and bottom types. Hyperspectral in situ reflectance was measured at both the top and bottom of the water column to examine the effects of the intervening water layer. A radiative transfer model was used to predict the top-of-the-water column reflectance from a large number of close-range measured bottom spectra. The measured and modeled hyperspectral reflectance spectra were examined separately to compare the degree to which different substrate types can be discriminated once the water column is "added" to the spectra. The classification accuracy assessment indicated that the ability to discriminate benthic habitat based on hyperspectral characteristics is limited when the effects of the water column are included as the kappa statistic drops from 0.70 to 0.49. © 2002 Elsevier Science Inc. All rights reserved.