High‐resolution three‐dimensional ground‐penetrating radar imaging of surface masonry arrangement in frescoed Roman walls at Pompeii

Abstract

The widespread presence of frescoes in newly excavated domus at Pompeii conceals the wall masonry arrangement, preventing direct geometric survey while excluding invasive diagnostic approaches. Reliable knowledge of masonry geometry is nonetheless essential for structural assessment and conservation planning in a seismically active region. This study assesses the feasibility of high‐frequency three‐dimensional (3D) ground‐penetrating radar (GPR) for non‐destructive imaging of Roman construction techniques concealed beneath frescoed plaster layers under strict field conservation constraints. A systematic experimental campaign was conducted on twelve plastered walls representing six Pompeian construction techniques with varying degrees of geometric regularity. Data were acquired using a 3 tGHz antenna in contact mode, with a dedicated positioning system achieving an inline and crossline spatial sampling compliant with the Nyquist theorem, and a textile coupling interface developed in collaboration with the Park's conservators to ensure safe acquisition on fragile decorated surfaces. Results demonstrate that geometric imaging of concealed masonry is feasible under the investigated conditions. Imaging quality is influenced by two factors: the geometric regularity of the construction technique and the electromagnetic impedance contrast between mortar and units. Plaster heterogeneity introduces additional local perturbations that partially affect signal quality. These results provide an operational framework linking acquisition design, material properties and imaging performance, supporting the systematic application of high‐frequency 3D GPR to the decorated walls of Pompeii.