ABSTRACT
Vegetation properties are often measured by converting a reŸectance spectrum into a single number value or vegetation index (VI). Hyperspectral, or narrowband [1], vegetation indices (HVIs) include narrower band features or wavelengths only captured by hyperspectral instruments (e.g., [2]). Vegetation properties measured with HVIs can be divided into three main categories: (1) structure; (2) biochemistry; and (3) plant physiology/stress. Measured structural properties include fractional cover, green leaf biomass, leaf area index (LAI), senesced biomass, and fraction absorbed photosynthetically active radiation (FPAR) [3-5]. A majority of the indices developed for structural analysis were formulated for broadband systems and have narrowband, hyperspectral equivalents. Biochemical properties include water, pigments (chlorophyll, carotenoids, anthocyanins), other nitrogen-rich compounds (e.g., proteins), and plant structural materials (lignin and cellulose) [6-8]. Physiological and stress indices measure subtle changes due to a stress-induced change in the state of xanthophylls [9], changes in chlorophyll content [10], Ÿuorescence [11], or changes in leaf moisture [12]. In general, biochemical and physiological/stress indices were formulated using laboratory or œeld instruments (≤10 nm spectral sampling) and are targeted at very œne spectral features. As a result they are strictly hyperspectral. The one exception is indices developed for water.
