A ground-penetrating radar survey for archaeological investigations in an urban area (Lecce, Italy)

A ground-penetrating radar (GPR) survey, using mostly a 500 MHz antenna, wa s carried out in an urban area (Lecce, Italy) to obtain a detailed characte rization of the most superficial layers, where presumably archaeological st ructures are buried, and to quickly identify anomalous zones for excavation . In the area, the presence of remnants of a historical Franciscan friary ( built in 1432 and pulled down in 1971) and, probably, of more ancient (Roma n and/or Messapic) features was expected. The geological setting (mainly we t calcarenite named "Pietra Leccese'') was not the most favourable for the application of GPR methodology because of an expected high attenuation of e lectromagnetic energy. The low penetration depth of the signal, not exceedi ng 1 m and even using a 100 MHz antenna, made it possible to obtain informa tion only between the ground level and the top of the calcarenitic basement . Data. recorded along parallel profiles, 1 m spaced, prevented the clear i dentification of the walls of the historical building constructed in "Pietr a Leccese'' blocks, because of the weak contrast in the electromagnetic par ameters with respect to the hosting material. On the other hand, the analys is of the radar sections allowed for identification and reconstruction of t he shape and extension of a barrel-vault cavity, subsequently confirmed by archaeological excavations. Time slice representations were used as a tool to locate other features including modern-day urban utilities and the plani metric development of the barrel-vault cavity. (C) 2000 Elsevier Science B. V. All rights reserved.