Developing a Neural-network-based "BRDF" Tool for the UAE Coastal and Inland Zones

The reflected radiation by observed surface is highly dependent on both sun illumination and satellite observation angles. These two angles are also described, respectively, as incident and reflected angles. The geometry-dependence of surface reflectance is usually corrected by a tailored Bi-directional Reflectance Distribution Function (BRDF). It is the most common tool used to eliminate or to reduce the effects of sun-sensor geometry on the reflected radiation. Generally, BRDFs are derived empirically (or semi-empirically) for a specific land cover by analyzing a large set of observations (training set) made under different illumination and observation angles. This approach involves fitting the model to collected observations and inverting it. However, obtaining a generalized BRDF for a geostationary sensor becomes more complicated due to the wide range of variation of both illumination and observation angles compared to polar orbiting platforms.