Radiative transfer and hyperspectral remote sensing in optically shallow waters

Richard C. Zimmerman, Ph.D.
Moss Landing Marine Laboratories

Wednesday, December 20, 2000
3:00 p.m.—Pacific Forum

rRemote sensing offers a rapid method for surveying large expanses of optically shallow waters, but the limitations of multispectral sensors have not provided sufficient spectral resolution necessary for accurate bottom type characterization or resource assessment in coastal waters. We are developing algorithms to identify submarine benthic organisms and quantify their abundance in optically shallow waters from remote sensing data sets produced by airborne hyperspectral remote sensing instruments, such as Portable Hyperspectral Imager for Low Light Spectroscopy (PHILLS), Hyperspectral Mapper (HyMap) and waterborne hyperspectral sensors that can be towed behind a vessel. Remote sensing signals are being characterized against in situ measures of bottom reflectance and upwelling radiance and theoretical radiative transfer calculations. Fourth derivatives of hyperspectral data sets provided characteristic signatures at a number of wavelengths for identifying the presence and abundance of seafloor organisms in remotely sensed pixels using second order polynomial equations. Effects of depth and suspended water column components (e.g. phytoplankton, sediment) on algorithm accuracy are being explored using both numerical simulation and field observations. Validation of the algorithm are currently under way in tropical (Bahamas) and temperate (Monterey Bay) areas vegetated by seagrasses and seaweeds using aircraft overflights and surface buoys mounted with hyperspectral radiometers for measuring the remotely sensed reflectance.

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