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, propagat ion, and scattering in geological materials as well as accurate knowle dge of the reflection characteristics of various target anomalies embe dded in such materials. GPR responses and survey profiles are often in terpreted on the basis of theoretical estimates and numerical simulati on models of electromagnetic wave propagation in simplified representa tions of ground materials and by using idealized target contrasts and geometries. Alternatively, field experiments performed under controlle d test conditions can also be effective in demonstrating GPR system pe rformance capabilities and in providing quantitative measurements in r ealistic geologic formations. Experimental research at the University of Rome ''La Sapienza'' and at the Italian National Research Council w ere initiated to develop a basic understanding of the radiation and sc attering characteristics of VHF pulse-mode GPR signals in earth materi als and in air with emphasis on antenna ground coupling and target bac kscatter responses. The results of the experimental measurements condu cted in air provided baseline information on the GPR system and target reflections under lossless propagation conditions. Target response me asurements at various burial depths provided a systematic data base fr om which target responses, propagation parameters of the medium, and r elevant data processing techniques were evaluated to gain useful insig hts into their interpretations. Other more advanced experimental tests are planned for the future.