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Many rockfall simulation software provide great flexibility to the user at the expense of a hardly achievable parameter unification. With sensitive site-dependent parameters that are hardly generalizable from the literature and case studies, the user must properly calibrate simulations for the desired site by performing back calculation analyses. Thus, rockfall trajectory reconstruction methods are needed. For that purpose, a computer-assisted videogrammetric 3D trajectory reconstruction method (CAVR) built on earlier approaches is proposed. Rockfall impacts are visually identified and timed from video footage, and are manually transposed on detailed high-resolution 3D terrain models that act as the spatial reference. This shift of reference removes the dependency on steady and precisely positioned cameras, ensuring that the CAVR method can be used for reconstructing trajectories from witnessed previous records with nonoptimal video footage. For validation, the method is applied to reconstruct some trajectories from a rockfall experiment performed by the WSL Institute for Snow and Avalanche Research SLF. The results are compared to previous ones from the SLF and share many similarities. Indeed, the translational energies, bounce heights, rotational energies and impact positions against a flexible barrier compare well with those from the SLF. Interestingly, only dissipative impact processes are observed with the CAVR method, contrary to the previous results from the SLF. The comparison shows that the presented cost-effective and flexible CAVR method can reproduce proper 3D rockfall trajectories from experiments or real rockfall events.

This work focuses on the in-depth reconstruction of the full set of parameters of interest in single-block rockfall trajectories. A comprehensive understanding of rockfall trajectories holds the promise to enhance the application of numerical models for engineering hazard analysis. Such knowledge is equally important to investigate wider cascade problems in steep terrain. Here, we present a full four-dimensional trajectory reconstruction of the “Chant Sura” rockfall experiment performed with EOTA221 norm rocks. The data analysis allows a complete kinematic description of a rock's trajectory in real terrain and underscores the physical complexity of rock–ground interactions. In situ accelerometer and gyroscope data are combined with videogrammetric and unmanned aerial-systems mapping techniques to understand the role of rock rotations, ground penetration and translational scarring in rockfall motion. The exhaustive trajectory reconstruction provides information over the complete flight path such as translational velocity vectors, angular velocities, impact duration and forces, ballistic jump heights, and lengths. The experimental data provide insight into the basic physical processes detailing how rotating rocks of general shape penetrate, rebound and scar ground terrain. In future, the data will serve as a calibration basis to enhance numerical rockfall modelling.