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

Abstract

Three different non-invasive techniques, namely Structure from Motion (SfM) photogrammetry, Terrestrial Laser Scanner (TLS) and ultrasonic tomography integrated with petrographic data, were applied to characterize two rock samples of a different nature: A pyroclastic rock and a carbonate rock. We started a computation of high-resolution 3D models of the two samples using the TLS technique supported by a digital SfM photogrammetry survey. The resulting radiometric information available, such as reflectivity maps, SfM photogrammetry textured models and patterns of geometrical residuals, were interpreted in order to detect and underline surface materials anomalies by a comparison of reflectance and natural colour anomalies. Starting from the 3D models from previous techniques, a 3D ultrasonic tomography on each rock sample was accurately planned and carried out in order to detect internal defects or sample heterogeneity. The integration of the above three geophysical non-invasive techniques with petrographical data—especially with the textural characteristics of such materials—represents a powerful method for the definition of the heterogeneity of the rocks at a different scale and for calibrating in situ measurements.

3D Imaging of CRP and Ultrasonic Tomography to Detect Decay in a Living Adult Holm Oak (Quercus ilex L.) in Sardinia (Italy)

“…In fact, generally speaking, during a CRP survey, a set of good quality 2D photo images are taken, using consumer-grade cameras, all around a tree or plant under study, at short distances (1-3 m), in different station points, evenly spaced at an average mean distance of 1 m between them, with the camera on a tripod. Single lens commercial digital cameras can be used; images must be aligned in the best way and then used to compute dense point clouds representing the studied tree, texturized with natural colors [3,4,[23][24][25]. These clouds can be successively post-processed with the aid of facilities for point cloud processing, derived from terrestrial laser scanner (TLS) methodology, for example.…”

“…The CRP technique is based on the well-known structure from motion (SfM) photogrammetry method and is performed essentially with the application of computer vision and computer graphic algorithms. CRP is a passive method that can also be applied as a stand-alone technique, because a priori information on the position of the cameras is generally not necessary, nor is camera orientation, calibration or the presence on the scene of geo-referred reference points [23][24][25]. The final 3D CRP models made available are useful for comparisons, animation, movies, measurements and conservation of the memory of the shape of trees in time as well as chronological evolution of the displacement of the tree.…”

“…In addition, the evaluation of the possibility of preventing the instability and failure of standing trees is of great importance in forestry. This target can be achieved by ultrasonic methods, largely employed to detect the elastic characteristics of different materials (e.g., stone, concrete, wood), although the interpretation of the data is very complex because elastic wave propagation strictly depends on the heterogeneity, porosity, density and other material properties [19,20,[25][26][27][28][29]. The presence of decay zones, small cavities and cracks or splits within the investigated materials are potential defects characterized by low ultrasonic velocity compared to the velocity in healthy materials.…”

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

“…The Pietra Forte represents the top facies of the upper Miocene Calcari di Cagliari Auct. (Gandolfi and Porcu, 1967;Cherchi, 1974). This lithology is characterized by well cemented and poorly porous biohermal and biostromal shelf limestones.…”

TLS and SfM Approach for Bulk Density Determination of Excavated Heterogeneous Raw Materials

“…The complete characterization of rock masses using advanced remote sensing technologies like LiDAR to detect the rock mass together with discontinuities was highlighted by Riquelme et al [9]. Fais et al utilized the SfM photogrammetry and TLS as non-invasive techniques to characterize various rock samples [10]. A comprehensive evaluation of the quality of digital elevation models (DEM) generated using UAV SfM photogrammetry was done by Blistan et al [11].…”