Angular variation of the model parameters of hyperspectral remote-sensing reflectance
ZhongPing
Lee, Naval Research Laboratory, zplee@nrlssc.navy.mil
(Presenting)
Deric
Gray, Naval Research Laboratory, deric.gray@nrlssc.navy.mil
Bertrand
Lubac, University of Southern Mississippi, bertrand.lubac@hotmail.com
Alan
Weidemann, Naval Research Laboratory, alan.weidemann@nrlssc.navy.mil
Remote-sensing reflectance (Rrs) of optically deep waters, either measured above or below the sea surface, is commonly described as a function that is proportional to the ratio (u) of backscattering coefficient to the sum of absorption and backscattering coefficients. The value of the proportional parameter (g, also called f/Q in literature), depends on various factors that including sea-surface state, water’s scattering and absorption properties, and viewing vs illuminating geometries. This latter factor is described as “bi-directional effects”. Because the viewing geometry of remote sensors varies, it is necessary to understand, and to analytically model its effects to Rrs. For Case-1 waters, and for fixed concentrations of chlorophyll and fixed spectral bands, Morel and Gentili (1993) and Morel et al (2002) have constructed a Look-Up-Table for the corresponding g values. For continuously varying (or hyperspectral) optical properties, Gordon et al proposed a two-parameter analytical model for nadir-viewed Rrs. Here, from extensive simulations by HYDROLIGHT, and based on recently measured particle phase functions, we present the relationship between Rrs and u for angles within the remote-sensing domain. In particular, we present model comparisons between the traditional two-parameter approach and a three-parameter formula.
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