A common method to identify or model the dominant directional reflective properties of a surface is the bidirectional reflectance distribution function (BRDF). BRDF describes the angular behavior by which light interacts with surfaces. Remote sensing technology has advanced to the stage where hyperspectral sensors, with hundreds of separate wavelength bands, are fairly common. This necessitates examining BRDF in the hyperspectral regime, which implies examining the directional reflective properties of hundreds of narrowly spaced wavelength bands.
In this dissertation I hypothesize that beach sand BRDF is wavelength dependent. Principal component analysis (PCA) and correlation matrix analysis of in situ measurements were used to test whether the spectral variability in the visible, near-infrared and shortwave directional reflectance factor of beach sands with and without freshwater surface films are wavelength dependent. The hyperspectral BRDF of beach sands exhibit weak spectral variability, the majority of which can be described with three to four broad spectral bands. These occur in the absence of a water layer on top of the sand in three wavelength ranges of 350-450 nm, 700-1350 nm, and 1450-2400 nm. When observing sheet flow on sand, a thin layer of water enhances reflectance in the specular direction at all wavelengths, and that spectral variability may be described using four spectral band regions of 350-450 nm, 500-950 nm, 950-1350 nm, and 1450-2400 nm. Spectral variations are more evident in sand surfaces of greater visual roughness than in smooth surfaces, regardless of sheetflow.
|Advisor:||Houser, Paul R., Ronald, Resmini G.|
|Commitee:||Bachmann, Charles M., Griva, Igor, Ronald, Resmini G.|
|School:||George Mason University|
|Department:||Earth Systems and Geoinformation Sciences|
|School Location:||United States -- Virginia|
|Source:||DAI-B 78/06(E), Dissertation Abstracts International|
|Subjects:||Statistics, Optics, Remote sensing|
|Keywords:||Beach sands, Spectral BRDF, Wavelength dependence|
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