PHOTOGRAMMETRIC DEVELOPMENT OF THE THRESHOLD WATER AT THE DAM ON THE VISTULA RIVER IN WLOCLAWEK FROM UNMANNED AERIAL VEHICLES (UAV)

Barrage in Wloclawek (Poland) was designed by Hydroprojekt and built in the years of 1962-1970 as the first stage of the planned Lower Vistula Cascade. Cascade design assumed the construction of 8 dams in Wyszogrod, Plock, Wloclawek, Nieszawa (Ciechocinek as an option), Solec Kujawski, Chelmno, Opalen and Tczew. Nieszawa dam was supposed to ensure the maintenance of an adequate free surface of water below the right dam in Wloclawek. Lower Vistula Cascade was not built, and until nowadays the dammed role is realized by the water threshold downstream the dam in Wloclawek, in its immediate vicinity. This threshold is a subject of a particular concern and photogrammetric analysis, presented in the article. Technical aspects and condition of the water threshold are related to the stability of the dam on the Vistula River in Wloclawek. Currently, the investment process was launched and it is aimed to change the development of Lower Vistula area. The investment realization is connected with the renovation of the dam on the Vistula River and it should help to change the role of the threshold in Wloclawek. At the same time, the awareness and qualitative evaluation of the threshold are required. Due to the difficulties in access to the threshold and the limited time of its unveiling, the photogrammetric method using Unmanned Aerial Vehicle (UAV) seemed to be effective and available for quick registration and validation of the threshold. The authors present the photogrammetric preparation which reflects the threshold condition. The realization was performed on the basis of 70 non-metric photos taken from the UAV. As part of the article, the technological problems and their solutions related to planning the run-in, as well as the description of the measurement method combining the photogrammetric and geodetic preparations (tachymeter measurement using TotalStation) are cited. The article includes the technical analysis of the enterprise and it indicates methods for the optimization of UAV use in the elaborations related to hydraulic engineering structures.