Forecasting the soil-dependent performance of ground-penetrating radar by means of a conventional field-moisture sensor

Abstract

On-site ground-penetrating radar (GPR) measurements with visual or acoustic real-time analysis cannot provide direct information whether or not GPR is suitable for the site at all. However, the knowledge of the limitations of a technique is of vital importance in the field in case of landmine, IED or UXO detection. For high-frequency (HF) GPR applications, various electromagnetic (EM) loss mechanisms in the soil play a crucial role. We investigated the EM properties of different soils using the coaxial transmission line (CTL) technique in the laboratory. We compared these results with measurements based on time-domain reflectometry (TDR) and direct current (DC) electrical conductivity measurements. We found that the absorption of EM energy in the soil cannot be described by DC electrical conductivity alone since dielectric relaxation mechanisms prevail at high frequencies. In order to predict the soil-dependent performance of GPR, we propose a conventional, relatively inexpensive, soil-moisture field sensor based on TDR as an alternative to the time consuming laboratory measurements. The TDR probe was calibrated by means of the CTL technique and measures the intrinsic attenuation as well as the relative dielectric constant. Comparisons between the GPR performance forecast carried out by on-site TDR measurements and the experimental GPR performance shows a promising correlation.