Atmospheric Effects in Satellite Imaging of Mountainous Terrain
Massachusetts Institute of Technology, Artificial Intelligence Laboratory, 1982 - Albedo - 85 pages
It is possible to obtain useful maps of surface albedo from remotely-sensed images by eliminating effects due to topography and the atmosphere, even when the atmospheric state is not known. A simple phenomenological model of earth radiance that depends on six empirically determined parameters is developed under certain simplifying assumptions. The model incorporates path radiance and illumination from sun and sky and their dependencies on surface altitude and orientation. It takes explicit account of surface shape, represented by a digital terrain model, and is therefore especially suited for use in mountainous terrain. A number of ways of determining the model parameters are discussed, including the use of shadows to obtain path radiance and to estimate local albedo and sky irradiance. The emphasis is on extracting as much information from the image as possible, given a digital terrain model of the imaged area and a minimum of site-specific atmospheric data. The albedo image, introduced as a representation of surface reflectance, provides a useful tool to evaluate the simple imaging model. Criteria for the subjective evaluation of albedo images are established and illustrated for Landsat multispectral data of a mountainous regions of Switzerland. (Author).
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Determining Model Parameters
Generation of Albedo Images
3 other sections not shown
albedo image altitude profile approximation Artificial Intelligence Artificial Intelligence Laboratory associated histogram assumed assumptions atmospheric effects atmospheric optics atmospheric radiometric quantities B. K. P. Horn calibration targets computed albedo Dent de Morcles determining the model digital elevation model digital terrain model Es(z exponential curve exponential forms extraterrestrial solar irradiance Figure horizontal surface illumination image irradiance image-forming equation imaging model imaging process Landsat MSS linear Lp(z minimum sensor radiance model parameters Morcles region mountainous terrain multispectral scanner mW cm-2 obtained optical depth optical thickness path radiance R. J. Woodham radiance and sky radiative transfer Rayleigh and aerosol reflectance map remote sensing satellite image scale height scattering scene sea-level shadow albedo shadowed targets single-scattering sky irradiance skylight solar zenith angle spectral sunlit and shadowed sunlit targets surface albedo surface normal surface reflectance synthetic image target albedo target radiance topography Turner-Spencer U.S. Standard Atmosphere USSA vertical transmission wavelength