Ground-penetrating radar characterization of water as a function of frequency, salinity and temperature

We conducted a laboratory experiment to test the ground penetrating radar (GPR) full-waveform forward and inverse modeling approach for electromagnetic wave propagation in water. The GPR system consisted of a vector network analyzer combined with an air-launched, 0.8-2.2 GHz horn antenna, thereby setting up an ultra wideband stepped-frequency continuous-wave radar. The apparent frequency-, salinity-, and temperature-dependent dielectric permittivity and electrical conductivity of water were estimated by using existing electrical models. Using these models, the radar data could be simulated and a remarkable agreement was obtained with the laboratory measurements. Neglecting the frequency-, salinity-, and temperature-effects led to less satisfactory results, especially regarding signal amplitude. Inversion of the radar data permitted to reconstruct the air and water layer thicknesses, and to some extent, the water electrical properties. This analysis particularly showed the benefit of using proper water electrical models compared to commonly used simplified approaches in GPR forward and inverse modeling.