Here we are today at the Tseuzier dam in Valais, Switzerland to start an inspection project in collaboration with ESR. We are at about 1800 metres altitude the top of the dam is about 280 metres long and on this side is 130 metres tall making a total surface area of 17,000 square metres to inspect which will take us about 50 flights. So this project presents us with several challenges the changeable weather conditions at this altitude the scale of the project and the irregular shape of the dam. The features that make this project possible are the distance lock, here set up at 3.7 metres giving us a resolution of 0.6 millimetre per pixel. To ensure the overlap we use the autotrigger and also the cruise control set up at 0.2 metre per second so the operator just has to keep the drone in the flight line. When we prepare the project, to ensure a sufficient overlap, we calculated that we needed to do a vertical flight line every 3 metres. So, we just put some marks every 3 metres all along the dam. At the middle of the dam, we take the drones down to -75 metres below take-off taking pictures the whole time on the way back up, which takes about 17 minutes. Visual observation is an essential and high-priority part of monitoring and operating a dam. any detection of an anomaly is immediately taken into account by the monitoring team, and can trigger measures being taken to assure the safety of the structure. Today, dam engineers perform their inspections using a basket. They are lowered down onto the air side of the dam and create detailed drawings on paper. Here we have an example of the documents obtained: 150 pages of drawings created by our staff in the office, based on initial inspections using the basket. So with 7000 photos taken we finished the inspection, now back to the office to process the data. The inspection performed at the Tseuzier dam has allowed us to obtain a high-resolution image of the structure’s entire air side, with the ability to observe cracks inferior to 0.5 millimetres [0.02 in] in size; a quality that is exceptionally high. The availability of a high-definition picture of the entire air-side of the dam is a very interesting contribution to our work.
It gives us a record of the dam’s condition at a given instant and enables work to continue in the office afterwards, re-examining and refining the record, something that cannot be done at all today. Furthermore, future inspection campaigns can be carried out using the exact same
shooting conditions, meaning we will be able to make absolutely reliable comparisons, a major benefit when monitoring a dam, tracking its degradation, the evolution of certain cracks, the supporting rock, and degradation of the surrounding cliffs. Taking into account the quality of the results obtained, the use of drones for the monitoring and inspecting of dams seems to have a bright future. We expect supervisory authorities will recommend their use when establishing reference records and recording future conditions, which will allow us to better monitor the progression of phenomena within the dams.