The use of an unmanned aerial vehicle for fracture mapping within a marble quarry (Carrara, Italy): photogrammetry and discrete fracture network modelling

Abstract

This paper describes the use of a drone in collecting data for mapping discontinuities within a marble quarry. A topographic survey was carried out in order to guarantee high spatial accuracy in the exterior orientation of images. Photos were taken close to the slopes and at different angles, depending on the orientation of the quarry walls. This approach was used to overcome the problem of shadow areas and to obtain detailed information on any feature desired. Dense 3D point clouds obtained through image processing were used to rebuild the quarry geometry. Discontinuities were then mapped deterministically in detail. Joint attitude interpretation was not always possible due to the regular shape of the cut walls; for every discontinuity set we therefore also mapped the uncertainty. This, together with additional fracture characteristics, was used to build 3D discrete fracture network models. Preliminary results reveal the advantage of modern photogrammetric systems in producing detailed orthophotos; the latter allow accurate mapping in areas difficult to access (one of the main limitations of traditional techniques). The results highlight the benefits of integrating photogrammetric data with those collected through classical methods: the resulting knowledge of the site is crucially important in instability analyses involving numerical modelling

How do we see fractures? Quantifying subjective bias in fracture data collection

“…Finally, window sampling is a technique all fractures within a given sample area (window) are traced out either by hand, or on a computer, and the resulting traces used to calculate the fracture statistics (Pahl, 1981;Priest, 1993;Wu and D. 5 Pollard, 1995). This technique is often utilised to analyse remote-sampling data such as aerial photographs (Healy et al, 2017), Unmanned Arial Vehicle (UAV) images (Salvini et al, 2017), bathymetry (Nixon et al, 2012), or satellite imagery (Koike et al, 1998), as well as in outcrop studies (Belayneh et al, 2009). It has been suggested that a minimum of 110 fractures are sampled to be able to statistically describe the fracture network using window sampling (Zeeb et al, 2013).…”

Application of UAV in Topographic Modelling and Structural Geological Mapping of Quarries and Their Surroundings—Delineation of Fault-Bordered Raw Material Reserves

“…In the stability analysis of cliff faces, the identification of joint systems and fractures are key issues. The remote sensing techniques are capable of identifying these structural geological elements [30,37]. Novel methods and close range surveys using digital techniques include the use of thermo-camera [38], close-range photography [34,39], or TLS [40].…”

“…This is where the application of remote sensing techniques demonstrates many advantages. In the assessment of the structural geological conditions, these tools are often applied [29,41] for representing faults [37,42] or folds [43].…”

DroneBorne Hyperspectral and Magnetic Data Integration: Otanmäki FeTiV Deposit in Finland

“…Accordingly, a multitude of UAS applications [9] have emerged over the past five years including mine surveillance [10], slope stability assessment in mining [11], agriculture [12], infrastructure and construction work [13], archaeology [14], forestry [15], disaster monitoring [16], coastal environmental studies [17] and ground water research [18]. Digital elevation models obtained from UAS can deliver resolutions in (sub-)centimeter range, and are superior to conventional mapping techniques in terms of survey area, time, and target accessibility [19,20].…”