Polarization And Kinematic Effects In Azimuthal Investigations Of Linear Structures With Ground-Penetrating Radar

Azimuthal variations of the GPR response may be diagnostic of elongated subsurface targets.<br>We performed tests on two classes of targets of interest in archaeological and engineering<br>applications: walls (archaeological remains) and underground utilities (plastic and<br>metallic pipes). The objective of the study is the implementation and test of a procedure<br>for the identification of elongated subsurface targets by means of GPR which may<br>provide information on the properties of the materials and may be an effective alternative<br>at sites where logistic constraints prevent from the acquisition of conventional grids. We<br>analyzed the response of targets buried at different depths in soils ranging from clays to<br>coarse sands, to compare the performance of azimuthal Multi-Fold and conventional GPR<br>techniques. A 3-D azimuthal Multi-Fold (MF) G round Penetrating Radar (GPR) data acquisition<br>and processing scheme was implemented and tested. Bi-static co-polarized and<br>cross-polarized 200 MHz and 400 MHz antennas were rotated around a Common Mid Point<br>in steps of 10’ and 30”. We obtained an average 6000% fold at each azimuth by varying the<br>source-receiver offset in steps of 10 cm. The amplitude of the radar response and the radar<br>velocities measured by means of Common Mid Point analysis exhibit sinusoidal variations.<br>The range of amplitude and velocity can be effectively used to discriminate among targets<br>of different characteristics. The location of maxima and minima in the (a) amplitude and<br>(b) amplitude-velocity responses can be used to evaluate the strike of the subsurface targets<br>in case of small and large radar cross-section respectively.<br>KEYWORDS<br>Ground Penetrating Radar - Multi-azimuth - Multi-fold - Velocity analysis - Amplitude analysis