Abstract
Abstract. UAVs are expected to be particularly valuable to define topography for natural slopes that may be prone to geological hazards, such as landslides or rockfalls. UAV-enabled imagery and aerial mapping can lead to fast and accurate qualitative and quantitative results for photo documentation as well as basemap 3D analysis that can be used for geotechnical stability analyses. In this contribution, the case study of a rockfall near Ponti village that was triggered during the November 17th 2015 Mw 6.5 earthquake in Lefkada, Greece is presented with a focus on feature recognition and 3D terrain model development for use in rockfall hazard analysis. A significant advantage of the UAV was the ability to identify from aerial views the rockfall trajectory along the terrain, the accuracy of which is crucial to subsequent geotechnical back-analysis. Fast static GPS control points were measured for optimizing internal and external camera parameters and model georeferencing. Emphasis is given on an assessment of the error associated with the basemap when fewer and poorly distributed ground control points are available. Results indicate that spatial distribution and image occurrences of control points throughout the mapped area and image block is essential in order to produce accurate geospatial data with minimum distortions.
Highlights
Unmanned aerial vehicles (UAVs) are expected to be valuable to define topography of natural slopes that may be prone to geological hazards (Niethammer et al 2012, Murphy et al 2014, Greenwood et al 2016, Zekkos et al 2016)
The case study of a rockfall near Ponti village that was triggered during the November 17th 2015 Mw 6.5 earthquake in Lefkada, Greece is presented with a focus on the 2D/3D basemap development for use in rockfall analyses
The spatial precision of the rasterised Digital Elevation Model (DEM), which is necessary for 3D rockfall analysis and the accuracy of the simulated kinematics decrease with increasing cell size in the raster map
Summary
Unmanned aerial vehicles (UAVs) are expected to be valuable to define topography of natural slopes that may be prone to geological hazards (Niethammer et al 2012, Murphy et al 2014, Greenwood et al 2016, Zekkos et al 2016). UAV-enabled imagery and mapping can lead to fast and accurate qualitative and quantitative results for photo documentation as well as basemap analysis that can be used for geotechnical stability analyses. In this contribution, the case study of a rockfall near Ponti village that was triggered during the November 17th 2015 Mw 6.5 earthquake in Lefkada, Greece is presented with a focus on the 2D/3D basemap development for use in rockfall analyses. The main disadvantage of 2D analysis is that the influence of the topographic relief on rock trajectories is not taken into account For this reason, the use of three-dimensional (3D) rockfall analysis is preferred. Experience has shown that a 1 m × 1 m resolution does not necessarily improve the quality while it increases the amount of data substantially
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