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Journal of Applied Remote Sensing

High spatial resolution spectrometry of rafting macroalgae (Sargassum)
Author(s): Karl H. Szekielda; George O. Marmorino; Jeffrey H. Bowles; David B. Gillis
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Paper Abstract

Data with 0.4-m spatial resolution acquired ~2 km off the southeast Florida coast using the airborne Portable Hyperspectral Imager for Low-Light Spectroscopy (PHILLS) have been analyzed with the objective of identifying drifting surface macroalgae (Sargassum) through its spectral signature in at-sensor radiance. The observed spectral features of Sargassum include a peak at a wavelength of ~0.570 µm and a photosynthetic 'red edge' between 0.673 and 0.699 µm. Sargassum also exhibits high radiance in the reflected near-infrared but is impacted by the atmospheric absorption bands of water vapor at 0.720 µm and oxygen at 0.756 µm. The spectral signature is clearest and largest in amplitude where the Sargassum occurs as small surface aggregations, or rafts, which tend to lie at the downwind ends of narrow Sargassum windrows. The quantity of floating Sargassum was estimated within a single pixel by linearly mixing a spectrum of Sargassum-free water with varying percentages of a spectrum from a pixel assumed completely filled with floating plants. For our study site about 2.3% of the ocean area is classified as having some Sargassum coverage, with pixels completely filled with Sargassum being rare (only 0.2% of the classified Sargassum pixels) and pixels with the least-resolvable amount of Sargassum (~10% filled) being the most common.

Paper Details

Date Published: 1 April 2010
PDF: 14 pages
J. Appl. Remote Sens. 4(1) 043529 doi: 10.1117/1.3431044
Published in: Journal of Applied Remote Sensing Volume 4, Issue 1
Show Author Affiliations
Karl H. Szekielda, The City Univ. of New York (United States)
George O. Marmorino, U.S. Naval Research Lab. (United States)
Jeffrey H. Bowles, U.S. Naval Research Lab. (United States)
David B. Gillis, U.S. Naval Research Lab. (United States)


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