High resolution 3-D modelling of cylinder shape bodies applied to ancient columns of a church

摘要

Abstract. The use of Non-Destructive Testing (NDT) applied toconstruction materials allows to highlight and characterize their features,especially in the case of old buildings. The multi-technique high resolution3D modelling described here is aimed to investigate the conservation stateof the central column of a colonnade in the ancient church of Saints Lorenzoand Pancratio, dating to about the second half of the thirteenth century andlocated in the old town of Cagliari (Italy). This column was considered ofinterest because its longitudinal axis deviates from its ideal position andit appears the most deteriorated. In this work we describe the integrated application of 3D diagnosticmethods, i.e. Terrestrial Laser Scanner (TLS), close range photogrammetry(CRP) and ultrasonic tomography supported by petrographic investigations.They were used to improve the diagnostic process of the conservation stateof the investigated column. The TLS technique was supported by CRP to obtaina natural colour texturized 3D model of the column. The geometrical anomalymaps derived from the data of the TLS-CRP survey show the presence of someanomalies worthy of attention. Starting from the 3D reconstruction withprevious techniques we planned and implemented a 3D ultrasonic tomography.Ultrasonic tomography proved to be a successful tool in identifying internaldefects, as well as the presence of voids and flaws within the materialsthrough the analysis of the propagation of ultrasonic waves. The integration of the three non-invasive techniques supported bypetrographical analyses demonstrates its potential in reducing ambiguitiessince each technique brings its clue to the overall diagnostic process.