Progress in Electromagnetic Research Symposium 2004, Pisa, Italy, March 28 - 31 497 Multi-fold Ground Penetrating Radar Imaging and Classification of Buried Targets for Environmental Applications M. Pipan University of Trieste – DISGAM Via Weiss, 1 Trieste, Italy pipan@units.it E. Forte University of Trieste – DISGAM Via Weiss, 1 Trieste, Italy eforte@units.it G. Dal Moro University of Trieste – DISGAM Via Weiss, 1 Trieste, Italy dalmoro@units.it M. Sugan University of Trieste – DISGAM Via Weiss, 1 Trieste, Italy msugan@units.it P. Gabrielli University of Trieste – DISGAM Via Weiss, 1 Trieste, Italy paologabrielli@yahoo.it I.Finetti University of Trieste – DISGAM Via Weiss, 1 Trieste, Italy finetti@units.it Abstract We use an integration of Single Fold (SF), Multi fold (MF), i.e. multi offset, Multi Azimuth (MA) and Multi Component (MC) or Polarimetric Ground Penetrating Radar (GPR) configurations to identify, characterize and classify targets of environmental interest. The results obtained in real and controlled conditions are validated by numerical simulations and excavation and show that MF/MA/MC GPR methods are fit for target classification in complex subsurface conditions. Introduction Ultra High Resolution (UHR) geophysical techniques are often used to study waste disposal sites, polluted areas, pipe leakages and brownfields in support of traditional invasive characterization methods based on sampling. Geophysical techniques provide information about physical properties of areas and volumes. This is their main advantage when compared with traditional invasive methods (TIM). TIM exploit chemical and physical analysis of samples obtained at the surface, or in boreholes and trenches, to provide information from single points in the area of study. Geophysical techniques can determine the characteristics of several physical properties over a grid, thus extending the areal significance of the TIM calibration. Ground Penetrating Radar techniques are well suited for site characterization in terms of vertical and horizontal resolution, depth of investigation and target identification capability. We tested GPR in several different environmental conditions and with different acquisition and analysis procedures. GPR is normally used only in Single Fold (SF) configuration, i.e. single offset. In this paper we use an integration of Multi Fold (MF), i.e. multi offset, Multi Azimuth (MA) and Multi Component (MC) or Polarimetric configurations for different environmental applications. In particular, we focus on the following common situations: 1) pipe localization, internal fluid characterization and pipe leakage detection; 2) waste disposal characterization; 3) industrial plant analysis. Methods We used an ultra-wide band (UWB) Ground Penetrating Radar (Malå Geoscience) equipped with shielded and unshielded antennas in the range of 200-800 MHz. We performed single offset acquisition (SF) and multiple common-offset-data acquisition to obtain Multi-Fold sections with average 1200 % fold. The range of offset was usually between 40-200cm, according to the frequency of the used antennas. The offset increment step was 5cm for 500 and 800 MHz antennas and 10cm for 200 and 250 MHz antennas. We exploited also Multi Azimuth and multi offset acquisition and analysis at single surface positions to obtain more traces related with the same depth point. The offset for this kind of analysis was in the range of 40-70cm and the angular step increment was 10°. As for Multi Component acquisition, we performed multi offset and multi azimuth acquisitions at selected locations using co-pole and cross-pole antennas configurations. We obtained several GPR datasets in the field and in a sandbox that is used as test site for experiments in controlled conditions. In the latter case we used a 2x2x1m box with homogeneous sand inside. We put plastic and metal pipes of different diameters in the sandbox and we filled them with air or fluids (fresh water, sea water, oil, gasoline). We also simulated a pipe leakage through the