Analysis of ALS Intensity Behavior as a Function of the Incidence Angle in Coastal Environments

The objective of this paper was to investigate and model the behavior of backscattered LiDAR intensity as a function of the incidence angle over coastal environments. Different surfaces, as flat sandy areas of contrasted water contents, coastal vegetation (salt marshes), sea surfaces, urban zones, have been investigated to define a general model. Different reflection models have been investigated, like Lommel-Seeliger, Ward, Oren-Nayar, and Hapke laws but either they do not allow to fit specular reflection, or they had too many parameters. The Torrance-Sparrow formulation is the only model that describes the intensity behavior of each representative surface, especially the specular signature of the water surface. This law integrates both diffuse and specular components, the latter being described by a microfacet distribution. Finally, to separate and identify the surfaces, we have established a decomposition method, based on a single microfacet distribution, to characterize, unambiguously, different surfaces.