Application of non-destructive geomatic techniques and FDTD modeling to metrical analysis of stone blocks in a masonry wall

► The use of GPR to define geometry of ashlar units. ► A comparison of GPR and laser scanning measurements to evaluate the accuracy of GPR. ► FDTD modeling to assist in the interpretation of the field GPR data. ► GPR showed its potential for metrical analysis of masonry walls. Ground-penetrating radar is a non-destructive geophysical technology that provides quantitative information about the subsurface structures. This technology shows many applications in the civil engineering field where its implementation is becoming very important. This work shows the validation of the geometric measurements performed using ground-penetrating radar by means of the precise geometric information provided by laser scanning (ground truth). Field work was done in a masonry wall provided by a local construction company. A total of 16 stone blocks were studied and the average of the accuracy values range between the 8.5% (horizontal) and 2.8% (vertical). The diffraction patterns produced by scattering events at the ashlar blocks made difficult to identify the edges of the blocks and, therefore, affected to the lower accuracy of the horizontal measurements. The finite-difference time-domain modeling was used to analyze the complex pattern of reflections obtained. The synthetic models were built from the orthoimage provided by laser scanning, and the results obtained confirmed the interpretation of the field data used for the accuracy study. In addition, a numerical test was performed including mortar inside the block joints instead of air. No differences in the interpretability were achieved.