Effective impedance of rough porous ground surfaces

Laboratory measurements at grazing angles of the impedance of sand surfaces containing artificial two-dimensional (2D) roughness are compared with predictions of an extended boss theory, which allows for incoherent scatter, randomness, and finite impedance effects. The data and predictions are found to be in reasonable agreement. The rough surface impedance model may be used, as an alternative to layering, to explain measurements where the reactance exceeds the resistance at low frequencies. The model also explains instances where the measured ground impedance tends to zero at higher frequencies. In addition, the model is found to predict features of measurements made with an elevated source and vertically separated receivers at a range of 30 m over cultivated ground surfaces.