Assessment of hydrogen fluoride damage to vegetation using optical remote sensing data
This research assesses damage to vegetation from accidental gaseous hydrogen fluoride leakage, through the analysis of spectral features of the damaged plants using digital aerial photographs and airborne hyperspectral imagery. The hyperspectral imagery was obtained 21 days after the leakage within visible and near-infrared wavelength range using CASI-1500 imager, and two aerial photographs composed of blue, green, red and near-infrared bands were also obtained in 2 October 2011 and 15 November 2012, respectively. The injuries on leaves and the outline of the leakage affected area were assessed by investigating vegetation index images calculated from the hyperspectral imagery and the aerial photograph obtained in 15 November 2012, with comparison to the index image calculated from the aerial photograph obtained in 12 October 2011. The affected areas were mainly distributed in the east of the leakage point, and this reflects predominant wind directions toward east during the leakage and within 24 hours after the leakage. In addition, the detailed changes in spectral reflectance curves of damaged vegetation were also investigated using the hyperspectral imagery. Paddy field and forest land were identified by cadastral map, and the reference areas for the comparison of the reflectance curve change were designated to each land cover type, by considering the most and least affected areas from the vegetation indices comparison results.