Numerical Modelling for Masonry GPR Surveys

Apparently complex reflection patterns can be common in GPR structural surveys. The main reasons for that are the regular geometrical shapes of structural and non-structural elements and the high frequency systems employed. These imply a greater direct and indirect signal interaction with materials: typical examples are multiples created by relatively thin layers, not otherwise visible with low frequency systems. This paper presents a case study where a radargram collected on a masonry wall of a historical building exhibited crisscross or “X” reflection patterns. It was the only wall in the building where these patterns were observed. Based on assumptions relying on a priori knowledge of the building structure gained by means of GPR scans conducted on adjacent walls, numerical modelling was employed to verify a hypothesis that could explain the observed data.