SOLAR-INDUCED FLUORESCENCE RETRIEVED FROM AVIRIS IMAGES OF URBAN AREAS OF KOLKATA AND HOWRAH IN INDIA

摘要

Recently Airborne Visible/Infrared Spectrometer Next Generation (AVIRIS-NG) was flown over several sites of India organized by Space Applications Centre, Indian Space Research Organization. This work analyzes the AVIRIS-NG images of Kolkata (around 22° 32' 30" N, 88° 19' 30" E) and Howrah (around 22° 33' 30" N, 88° 17' 30" E) for solar-induced fluorescence of vegetation. Hyperspectral radiance spectra over visible-near-infrared and shortwave infrared wavelengths were derived from the images for several vegetated and non-vegetated regions, the former being fluorescing. The extent of fluorescence was estimated by fluorescence line depth technique using oxygen absorption bands around 762 nm. The selection of band for fluorescence assessment was investigated for different combinations. The bands corresponding to the far-red fluorescence both in and outside the oxygen absorption bands were found to yield better result. The path radiance effect was minimized by subtracting the radiance values obtained from pixels containing waterbody. The quantity of fluorescence thus estimated was of the order of 1 Wm"2 sr-1um~The results were compared with the Orbiting Carbon Observatory-2 data for nearby areas.