Retrieving the propagation velocity of electromagnetic waves in a two‐layered medium through diffraction curves

Abstract This paper addresses the problem of retrieving the propagation velocities of electromagnetic waves in a non‐homogeneous soil made up of two layers separated by a not‐flat interface. The propagation velocities are estimated from GPR data gathered at the air–soil interface in common offset configuration. The well‐known diffraction hyperbola method is exploited for retrieving the propagation velocity in the shallower layer. Conversely, an extension of the diffraction hyperbola method is proposed to estimate the propagation velocity in the second layer (meant as the deeper one). The proposed approach accounts numerically for the refraction of the waves at the buried interface, which deforms the diffraction curve. The shape of the buried interface is accounted for by using abscissa‐time samples picked up from the data. The approach exploits theoretical aspects derived for a flat buried interface and empirically extends them to the case of a curved (smooth) buried interface. Experimental results in a controlled scenario are presented.