Terrestrial laser scanning and digital photogrammetry techniques to monitor landslide bodies

Photogrammetry and laser scanning, thanks to significant development in last years, are comparable surveying techniques to generate - without object contact and with a precision commensurate with scale - Digital Terrain Models (DTMs), a fundamental tool to detect, classify and monitoring landslides. The traditional way to survey the territory for landslide detection purposes is aerial or, in some cases, terrestrial photogrammetry, that permits to carry out 3D models of the terrain and, by means of DTMs comparisons, to realise multi-temporal studies. The massive introduction of modern digital photogrammetric workstations, with automatic matching procedures, allows for a rapid DTM production for landslide monitoring activities. On the other hand, the 3D reconstruction of the terrain with terrestrial laser scanning methods is another modern way to reproduce the natural surface of the ground with high accuracy and high automation. There are however some open problems concerning the elaboration of the data and the procedures to generate DTM starting from Digital Surface Models (DSMs), taking off vegetation, buildings, etc. The present work describes the terrestrial laser scanning and photogrammetric surveys realised on a small landslide body located on the Northern Apennines in Italy (municipality of Vergato, Bologna), an interesting case in order to test the laser scanning capabilities and the procedure of laser data processing, also in comparison with photogrammetry.