Retrieval of reflectance from 1989 airborne visible/infrared imaging spectrometer (AVIRIS) data using LOWTRAN 7 atmospheric models
AuthorPortigal, Frederick Peter
AdvisorElvidge, Christopher D.
Geological Sciences and Engineering
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This research has demonstrated that atmospheric models may be used to extract ground reflectance from AVIRIS data with an accuracy within one to three percent of an empirically based method. In this study a single ground target of known bi-directional reflectance was utilized in conjunction with a radiosonde atmosphere to produce a forced-fit function. This function, when applied to the data, compensates for differences between the LOWTRAN 7 model and AVIRIS radiance data which result from problems with the radiometric calibration. A model which uses only default LOWTRAN 7 options without the forced fit procedure was also tested and compared with the empirical calibration. This default LOWTRAN calibration is surprisingly accurate given the fact that the atmosphere used is the midlatitude summer urban model with 20 kilometer visibility, which would vary greatly from the actual atmospheric conditions at the time of the overflight. The empirical and LOWTRAN calibrations are then applied to pixels extracted from a Riparian forest over Stanford University’s Jasper Ridge Biological Preserve and a comparison is made with the laboratory reflectance spectra of green leaves for two of the forest’s dominant tree species, Salix Laevigata and Salix Lasiandra.
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