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COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- VISUAL DOCUMENTATION AND INSPECTION OF DAM SURFACES USING STATE-OF-THE-ART TOTAL STATIONS Slaven Kalenjuk1, Werner Lienhart1, Harald Wackenreuther2 1GRAZ UNIVERSITY OF TECHNOLOGY 2VERBUND HYDRO POWER GMBH AUSTRIA 1. INTRODUCTION Dam surveillance is crucial to minimize the risk of a dam failure. The International Commission on Large Dams (ICOLD) proposes guidelines to establish surveillance procedures, including instrumentation of sensors for monitoring and evaluating the data [1]. The overall assessment of dam safety comprises three major pillars: monitoring, visual inspections and checking & testing (Fig. 1). While special tests are due every one to five years, monitoring and visual inspections are required at frequent intervals. A typical monitoring setup consists of a variety of sensors, each of which complements the other and contributes to the model analysis. The mathematical models also take into account the sensor limitations (e.g. sensitivity, accuracy) and thus give a good estimate on the reliability of the results. By contrast, visual inspections highly depend on the inspector’s experience or performance. The resulting report, including photographs, drawings and comments, is subjective and may be incomplete and inaccurate, especially for the long-term documentation and inspection of the concrete surface of a dam’s downstream side. Consequently, emerging technologies, as laser scanning and digital imagery, gain more and more attention for addressing these problems. A comprehensive three-dimensional documentation of the dam proved beneficial in deformation monitoring as well as for surface documentation. For this purpose, researchers focused on using Unmanned Aerial Vehicles (UAVs), carrying a Single Lens Reflex (SLR) camera 774