Direct Determination of Electric Permittivity and Conductivity from Air-launched GPR Surface-reflection Data

(eng) Knowledge of the spatial distribution of surface soil-water content and its dynamics is important on many scales for research and applications in agriculture, hydrology, meteorology, and climatology. At the field scale of one hectare, it is difficult at present to obtain reliable estimates in an efficient way. A versatile method for determinating the electric permittivity of a volume just below the earth surface uses off-ground monostatic ground-penetrating radar (GPR) reflection data. This volume average can be called the surface-soil permittivity, and the permittivity and conductivity of the ground are determinated as close to the surface as possible given the bandwidth used in acquisition. it can be demonstrated that under reasonable conditions, in which the time-domain surface-reflection method works with satisfactory accuracy, the extended surface-reflection method performs better when used in the frequency domain. This method allows for accurate conductivity estimates when these conductivities can be obtained from full-waveform inversion.