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Use Of Spectral Distance, Spectral Angle, And Plant Abundance Derived From Hyperspectral Imagery To Characterize Crop Growth Variation
C. Yang
USDA-ARS

Vegetation indices (VIs) derived from remote sensing imagery are commonly used to quantify crop growth and yield variations. As hyperspectral imagery is becoming more available, the number of possible VIs that can be calculated is overwhelmingly large. The objectives of this study were to examine spectral distance, spectral angle and plant abundance derived from all the bands in hyperspectral imagery and compare them with eight widely used two-band or three-band VIs based on selected wavelengths for quantifying crop growth variability. Airborne hyperspectral images and yield monitor data collected from two grain sorghum fields were used for this study. A total of 64 VI images were generated based on the eight VIs and selected wavelengths for each field. Two spectral distance images, two spectral angle images and a pair of plant and soil abundance images were also created based on a pair of pure plant and soil reference spectra for each field. Correlation analysis showed that the modified soil-adjusted vegetation index (MSAVI) produced more consistent and higher r-values with yield than the other VIs among the selected bands. Spectral distance, spectral angle and abundance produced similar r-values to the VIs. The results from this study suggest that either a MSAVI image based one NIR band and one green band or a plant abundance image based on a pair of pure plant and soil spectra can be used to convert a hyperspectral image to a relative yield map.

Keyword: Hyperspectral imagery, Plant abundance, Plant growth, Spectral angle, Spectral distance, Spectral unmixing, Yield