Ground-penetrating radar resolution in cultural heritage applications

High-resolution methods are required in the non-destructive study of historical buildings, archaeological sites and cultural heritage structures in general. Ground-penetrating radar (GPR) is widely used in such studies. However, radar images of archaeological sites and cultural heritage architecture tend to be unclear and are difficult to interpret. Knowledge of the antenna's behaviour and the optimum expected resolution could help to interpret radar data and define a limit of the real resolution in field surveys. Laboratory tests could provide information about the optimum resolution for each specific antenna. The main goal of this study was to obtain experimental data under lab conditions and thus define the optimum resolution expected in radar surveys. This could then be considered as a limit in field surveys. All of the lab tests were performed using homogeneous media (water and sand) to avoid interference and clutter. As a result, simple images were obtained. The optimum resolution was defined from radar data acquired under these favourable, controlled conditions. In all cases, resolution was defined as the distance (considered as a function of wavelength) between two targets (in the vertical or horizontal axis) that were needed to obtain separate anomalies. All the optimum values were considered to define the limits of the survey resolution in the different cases presented in this paper. In each case, the optimum values were compared with the result and with the radar images to define the best approach to the expected resolution in architectural heritage surveys. To conclude, we define some experimental values of the optimum resolution, described in terms of wavelength. These experimental data are likely to provide a better approach than theoretical estimations.