Three-dimensional imaging from laser scanner, photogrammetric and acoustic non-destructive techniques in the characterization of stone building materials

Abstract

Abstract. When combined, the three-dimensional imaging of different physical properties of architectural monumental structures acquired through different methodologies can highlight with efficiency the characteristics of the stone building materials. In this work, we compound high resolution Digital Color Images (DCI) and Terrestrial Laser Scanner (TLS) data for a dense 3-D reconstruction of an ancient pillar in a nineteenth century building in the town of Cagliari, Italy. The TLS technique was supported by a digital photogrammetry survey in order to obtain a natural color texturized 3-D model of the studied pillar. Geometrical anomaly maps showing interesting analogies were computed both from the 3-D model derived from the TLS application and from the high resolution 3-D model detected with the photogrammetry. Starting from the 3-D reconstruction from previous techniques, an acoustic tomography in a sector of prior interest of the investigated architectural element was planned and carried out. The ultrasonic tomography proved to be an effective tool for detecting internal decay or defects, locating the position of the anomalies and estimating their sizes, shapes, and characteristics in terms of elastic-mechanical properties. Finally, the combination of geophysical and petrographical data sets represents a powerful method for understanding the quality of the building stone materials in the shallow and inner parts of the investigated architectural structures.

Characterization of Rock Samples by A High-Resolution Multi-Technique Non-Invasive Approach

“…The interpretation of the integrated geophysical data (Figure 9a-g and Figure 10a-g) proposed in this work needs to be constrained by petrographical and petrophysical data. The textural and compositional characteristics of the rocks, as well as the type, quantity and size of the pores affect the geophysical responses, as already recognized in previous works [11,45,69]. Therefore, the geophysical interpretation needs to be integrated with petrographical data in order to maximise the benefit that derives from applying the proposed non-destructive multi-technique approach for the characterization of stone materials.…”

“…As a general remark we need to point out that the patterns of the geometrical anomalies computed with the help of the two methodologies TLS and SfM photogrammetry on the studied samples show interesting analogies. In fact, in spite of the fact that resolution of the two methods is different, the general shape of the residuals is quantitatively comparable [11].…”

“…Establishing the properties and state of conservation of stone materials can relate to many fields of research, from cultural heritage to architecture and also geological studies [1][2][3][4][5][6][7][8][9][10][11][12][13].…”

“…In this way it is possible to increase the accuracy of the dynamic elastic characterization of the rock samples while replacing some of the ordinary destructive tests. A similar integrated approach was recently applied in the cultural heritage field [11,30], but it has never been applied in the geophysical characterization of rock samples.…”

“…High-resolution 3D models computed with integration of TLS and SfM techniques provide precise information about the geometrical shape of studied objects, but also on a radiometric parameter called reflectivity or reflectance, a dimensionless ratio between the energy backscattered by the surface of the illuminated bodies and sensed by laser diode phase comparator and the incident energy emitted by the laser itself. The reflectivity varies with the colour of bodies but is also proportional to the roughness of the illuminated surfaces, and is often used to classify different component materials [9,11,19,[34][35][36][37][38].…”