De-Shadowing of Satellite/Airborne Multispectral and Hyperspectral Imagery

A de-shadowing technique is presented for multispectral and hyperspectral imagery over land acquired by satellite / airborne sensors. The method requires a channel in the visible and at least one spectral band in the near-infrared (0.8-1 μm) region, but performs much better if bands in the short-wave infrared region (around 1.6 and 2.2 μm) are available as well. Five major processing steps are employed : (1) the calculation of the covariance matrix and zero-reflectance matched filter vector based on atmospherically corrected surface reflectance data, (2) the derivation of the unscaled and scaled shadow function, (3) a histogram thresholding of the unscaled shadow function to define the core shadow areas, (4) a region growing to include the surroundings of the core shadow areas for a smooth shadow/clear transition, and (5) the de-shadowing of the pixels in the final shadow mask using the scaled shadow function. A radiative transfer code is employed in the last step to compute the de-shadowed surface reflectance imagery. Example images of hyperspectral airborne and multispectral spaceborne are presented.