GEOMONITORING OF A LARGE LANDSLIDE AT THE LÄRCHBERG / MURAU (AUSTRIA) WITH SELECTED GEOSPATIAL TECHNOLOGIES

In April 2001 a rock fall at the Lärchberg-Galgenwald with boulders of several cubic meters in size did occur, which reached until the 50 to 70 m wide apron of the Federal Highway B96. This event triggered the installation of a fivemeter-high protective dam and the start of a geodetic monitoring program based on rope extensometer measurements and a geodetic survey. This study area is used to test further methods of image processing-based monitoring and to show the advantages and disadvantages with the focus on the main area of the landslide. The two technologies used are structure-from-motion (SfM) and terrestrial laser scanning technology. Both systems work through contactless data acquisition by active and passive recording processes. A data set in the form of a point cloud and a digital surface model with a grid size of 10 cm, which are checked for accuracy on the basis of measured control points, was created across all methods. As a further approach, the fusion of the point clouds from the flight using an unmanned aerial vehicle (UAV) and the laser scan point clouds was carried out.