Atmospheric corrections of AVIRIS images with a procedure based on the inversion of 5S model

An atmospheric correction methodology was developed for correcting AVIRIS (Airborne Visible and Infrared Imaging Spectrometer) images that were acquired during the 1991 NASA/JPL campaign over “The Landes” (S.W. France). It is based on the inversion of the 5S atmospheric model, through an iterative approach that uses the Gauss Seidel principle. Adjacency effects are fully taken into account with the use of circular neighbourhoods, for each pixel, the radii of which vary with wavelength. Atmospheric optical parameters were estimated with in-situ atmospheric profile and visibility measurement combined with the 5S model. Due to the poor accuracy of the visibility parameter a procedure was developed for retrieving the aerosol optical depth directly from the remotely acquired image alone. At different wavelengths, the aerosol optical depth must be such that the reflectance of dark objects, which is supposed to lie in an a-priori defined interval, lead to the right apparent reflectances. For each pixel, the target reflectance is computed as the most probable. This approach led to the determination of an aerosol optical depth map, after some spatial interpolation. This map is used as an input parameter in the atmospheric correction algorithm. For all AVIRIS bands, convergence was attained after less than 5 iterations. Accuracy better that 0.54% was obtained with radii of neighbourhoods at least equal to 30 pixels in the visible region and 5 pixels in the near-infrared region. The use of these radii values resulted in reflectance variations as large as 60%, 40%, and 6% in the VIS, PIR and MIR regions, respectively