This paper represents the result of the IAEG C35 Commission “Monitoring methods and approaches in engineering geology applications” workgroup aimed to describe a general overview of unmanned aerial vehicles (UAVs) and their potentiality in several engineering geology applications. The use of UAV has progressively increased in the last decade and nowadays started to be considered a standard research instrument for the acquisition of images and other information on demand over an area of interest. UAV represents a cheap and fast solution for the on-demand acquisition of detailed images of an area of interest and the creation of detailed 3D models and orthophoto. The use of these systems required a good background of data processing and a good drone pilot ability for the management of the flight mission in particular in a complex environment.

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 three-dimensional (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.

Monitoring of geomorphic changes affecting sea cliffs poses a difficult challenge from a logistical point of view. Nevertheless, this activity is fundamental for the evaluation of cliff recession rates and the assessment of risk conditions affecting coastal settlements. Innovative geomatics techniques provide a valid contribution to detect cliff topographic modifications induced by erosion or landslide processes. This study presents a photogrammetric approach based on structure from motion (SfM) aimed at monitoring the geomorphic evolution of a coastal landslide that displaced about 40 000 m³ of material in southern Italy. The landslide was monitored for more than two years, comparing multitemporal 3D point clouds derived from SfM. The results of change detection analysis allowed quantifying the volumes of rocks and unconsolidated sediments mobilised by erosion processes after the main failure, and developing a sediment budget. The study highlighted the high erodibility of collapsed material, as well as the suitability of the adopted techniques for 3D change detection analyses.