Modeling of GPR signal and inversion for identifying the subsurface dielectric properties frequency dependence and effect of soil roughness

Research has focused on the development of a new integrated approach including ground penetrating radar (GPR) design, GPR signal forward modeling, and GPR signal inversion to estimate the dielectric permittivity and electric conductivity of the shallow subsurface (Lambot et al. [1], [2]). We propose to use an ultrawide band (UWB) stepped frequency continuous wave (SFCW) radar combined with an off-ground monostatic transverse electromagnetic (TEM) horn antenna. Forward modeling is based on linear system response functions for describing the antenna, and on the exact solution of Maxwell´s equations for wave propagation in a horizontally multilayered medium representing the subsurface. Model inversion, formulated by the classical least squares problem, is carried out iteratively using advanced global optimization techniques. The proposed approach is validated under laboratory conditions on a homogeneous sand subject to different water contents. The frequency dependence of the electric conductivity is characterized and the effect of soil roughness is analyzed.