Castellfollit de la Roca

The Castellfollit de la Roca escarpment is one of the best known areas of geological interest in Catalonia. The town sits on its characteristic basaltic columns, on which there is evidence of rockfalls, some of which are significant.

Since June 2021, the Georisk project team has been monitoring the northern escarpment using a photogrammetric system consisting of three Canon EOS 6D Mark II cameras with 105 mm focal length, located at a distance of approximately 170 m from the wall. The cameras take photographs every hour and send them in real time to a server via a 3G (Matas et al., 2022). Once the images are received, they are processed and compared with previous periods, so that movements in the columns, indicative of their possible subsequent fall, can be detected. Prior to the comparison of the images, a previous processing is necessary, since, in spite of the cameras being located in fixed positions, they suffer small variations due to wind and the influence of the temperature changes.

Working in the area is not easy. On the one hand, due to the existence of a lot of vegetation in some areas, not only on the wall itself, but also close to the river, which makes it difficult to see the wall. On the other hand, the northern orientation of this escarpment makes it difficult to take pictures, as the sunlight falls directly on the cameras, as well as the fog that usually appears in the area early in the morning.

Finally, the nature of the material means that its colour varies depending on the presence of water or changes in lighting.