FIELD EXPERIMENTS FOR CHARACTERIZATION OF GPR ANTENNA AND PULSE-PROPAGATION

Productive interpretations of ground penetrating radar surveys require an accurate understanding of electromagnetic wave radiation, propagation, and scattering in geological materials as well as accurate knowledge of the reflection characteristics of various target anomalies embedded in such materials. GPR responses and survey profiles are often interpreted on the basis of theoretical estimates and numerical simulation models of electromagnetic wave propagation in simplified representations of ground materials and by using idealized target contrasts and geometries. Alternatively, field experiments performed under controlled test conditions can also be effective in demonstrating GPR system performance capabilities and in providing quantitative measurements in realistic geologic formations. Experimental research at the University of Rome ''La Sapienza'' and at the Italian National Research Council were initiated to develop a basic understanding of the radiation and scattering characteristics of VHF pulse-mode GPR signals in earth materials and in air with emphasis on antenna ground coupling and target backscatter responses. The results of the experimental measurements conducted in air provided baseline information on the GPR system and target reflections under lossless propagation conditions. Target response measurements at various burial depths provided a systematic data base from which target responses, propagation parameters of the medium, and relevant data processing techniques were evaluated to gain useful insights into their interpretations. Other more advanced experimental tests are planned for the future.