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Influence of antenna configurations for GPR survey: information from polarization and amplitude versus offset measurements

Abstract Ground penetrating radar (GPR) images depend strongly on the relative geometry between the transmitter, the receiver and the subsurface reflectors. This dependence results from the directional properties of the antennae and from the sensitivity of the reflector to the polarization of the incident electromagnetic wave. In the present study, GPR data sets have been recorded using several 100 MHz antennae configurations, including transverse electric (TE) or transverse magnetic (TM) modes that have been used both parallel and perpendicular to the recording line. The images obtained show a high complementarity that provides more detailed information of the studied geological reflectors compared to the image derived from a single conventional acquisition configuration. Consequently, we compute pseudoprofiles that gather information derived from all acquisition modes, thus improving the GPR images. These pseudo-profiles are characterized by either a low directional degree of the antennae or a neutral acquisition mode. In addition, we have conducted a polarization analysis by surveying the studied profile twice with parallel and perpendicular antennae, in both modes (TE and TM). The comparison of these data sets provided three-dimensional (3-D) information on reflectors, particularly their depolarization properties. These studies clearly emphasize how multiconfiguration antennae surveys have the potential to improve GPR imaging and interpretation. Furthermore, polarimetric surveys have been carried out in order to explore further whether depolarization phenomena could explain observations of phase inversion and amplitude decrease on TE common mid-point gathers that would induce perturbations of the GPR images in the stacking procedure for multi-offset surveys.