Description: When any three-dimensional surface, e.g. a plant canopy is illuminated by a directional light source such as the sun, an angular reflectance distribution results that shows a narrow intensity peak in the direction of retro-reflection. This is called the Heiligenschein or hot spot (HS) of vegetation canopies and is caused by the absence of mutual shading of leaves when the observation direction coincides with the illumination direction. The angular intensity distribution of this hot spot, its brightness and contrast against the background, are therefore indicators of the plant's geometry. We show from experimental data and by modeling that the hot spot angular reflectance signature carries information about plant stand architecture that is often more distinctive for different plant species than their spectral signatures. 8 refs., 11 figs.
Date: January 1, 1988
Creator: Gerstl, S.A.W.
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