Estimation of the influence of disregarding the non-Lambertian Earth surface reflectance on the error in its reconstruction from satellite data
M.V. Tarasenkov, V.V. Belov, A.V. Shesterikova
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: Monte Carlo method, non-lambertian surface, radiative transfer, ground surface reflectance
Abstract
To perform accurate atmospheric correction (elimination of the distorting influence of the atmosphere) of satellite images, it is crucial to consider various factors that influence the received signal, including the non-Lambertian surface reflectance (the difference between surface reflection and Lambert's law, according which radiation is equally reflected in all directions and depends only on the irradiance of the surface and the reflectance). High-quality satellite information is important for solving a wide range of problems in monitoring the ground surface, such as forest condition, agricultural productivity, and others. In some algorithms, non-Lambertian reflection is taken into account after solving the problem in the Lambertian reflection approximation. In this case, the assumption is used that the adjacency effect (received radiation reflected from areas of the ground surface adjacent to the observed one and scattered in the atmosphere) is formed only by surfaces with Lambertian reflection. The calculations performed show that at S M ≥ 6 km, neglect of non-Lambertian reflection produces an error in determining the reflectance of no higher than 20.3%, neglect of non-Lambertian reflection in the formation of adjacency effect and additional illumination results in an error of no more than 12%, and neglect of non-Lambertian reflection in additional illumination, of no more than 1.4%. For more clear situations ( S M ≥ 6 km), the maximal error for similar models does not exceed 92, 14, and 1.2%, respectively. For solar zenith angles θsun ≤ 60° and angles of the optical axis of the receiving system θsun ≤ 60°, the errors do not exceed 30, 7.5, and 1%, respectively. The results prove the possibility of considering non-Lambertian reflection after taking into account adjacency effect and additional illumination of the ground surface in the Lambertian reflection approximation.
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