Abstract
Abstract. Steep, hardly accessible cliffs of rhyolite tuff in NE Hungary are prone to rockfalls, endangering visitors of a castle. Remote sensing techniques were employed to obtain data on terrain morphology and to provide slope geometry for assessing the stability of these rock walls. A RPAS (Remotely Piloted Aircraft System) was used to collect images which were processed by Pix4D mapper (structure from motion technology) to generate a point cloud and mesh. The georeferencing was made by Global Navigation Satellite System (GNSS) with the use of seven ground control points. The obtained digital surface model (DSM) was processed (vegetation removal) and the derived digital terrain model (DTM) allowed cross sections to be drawn and a joint system to be detected. Joint and discontinuity system was also verified by field measurements. On-site tests as well as laboratory tests provided additional engineering geological data for slope modelling. Stability of cliffs was assessed by 2-D FEM (finite element method). Global analyses of cross sections show that weak intercalating tuff layers may serve as potential slip surfaces. However, at present the greatest hazard is related to planar failure along ENE–WSW joints and to wedge failure. The paper demonstrates that RPAS is a rapid and useful tool for generating a reliable terrain model of hardly accessible cliff faces. It also emphasizes the efficiency of RPAS in rockfall hazard assessment in comparison with other remote sensing techniques such as terrestrial laser scanning (TLS).
Highlights
In the past years, technological development of Remotely Piloted Aerial System (RPAS) revolutionized the data gathering of landslide-affected areas (Rau et al, 2011), recultivated mines (Haas et al, 2016) and monitored coastal processes (Casella et al, 2016) and levee breaches (Brauneck et al, 2016) or road cuts (Mateos et al, 2016)
The present study focuses on the southern hillslope of the castle hill, where major rockfalls occurred in the recent past (Fig. 2)
The rhyolite tuff faces consist of moderately bedded ignimbritic horizons and brecciated lapilli tuffs according to our field observations (Fig. 6)
Summary
Technological development of RPAS revolutionized the data gathering of landslide-affected areas (Rau et al, 2011), recultivated mines (Haas et al, 2016) and monitored coastal processes (Casella et al, 2016) and levee breaches (Brauneck et al, 2016) or road cuts (Mateos et al, 2016). RPAS can be combined with terrestrial laser scanning (TLS) since both remote sensing tools provide high-precision terrain measurement (Fanti et al, 2013; Assali et al, 2014; Francioni et al, 2014; Neugirg et al, 2016; Manconi and Giordan, 2015). These tools can be used to validate height information derived by other technologies. These methods rely on understanding failure mechanisms and on predicting displacement of rock masses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
