“…Airborne laser scanning (ALS) and photogrammetry are two main techniques to obtain 3D data representing the surface of the terrain (Höhle and Höhle, 2009). Compared with airborne laser scanning, image acquisition in photogrammetry is mostly cheaper and more efficient in data acquisition flights (Hobi and Ginzler, 2012;Nurminen et al, 2013;Maltezos et al 2016). In many countries photogrammetric image blocks are captured anyway for administrative and planning purposes with decreasing time intervals, so the question is to what extent these data can be used to replace ALS data in various application domains such as Digital Terrain Model (DTM) acquisition (Ressl et al, 2016), forestry mapping (Mura et al, 2015), classification and object extraction (Tomljenovic et al, 2016;Dong et al, 2017), and 3D modeling (Xiong et al, 2015).…”