Remote Sensing Data for Monitoring Periglacial Processes in Permafrost Areas: Terrestrial Laser Scanning at the Rock Glacier Hinteres Langtalkar, Austria

This article discusses terrestrial laser scanning as a periglacial monitoring technique focusing on recent geomorphic changes at the near-terminus zone of the rock glacier Hinteres Langtalkar (N46°59’, E12°47’). This rock glacier shows high movement rates at its lower part since the mid-1990s thereby advancing over a prominent bedrock ridge into steeper terrain. The surface of this collapsing part of the rock glacier shows a very disturbed topography causing problems for terrestrial as well as remote sensing monitoring methods. Simple digital elevation model (DEM) differences only provide information about surface elevation changes. Optical flow detection in grey scale images (correlation based matching) are for instance solutions for acquiring information about vertical and horizontal motions. However, the lack of textural
information makes this approach non-applicable at this study area. Terrestrial laser scanning is completing the data set with distance measurements leading to 3D point clouds which are afterwards converted into accurate 3D models. Results show that the rapid movement of the lower part of the rock glacier decreased from maximum horizontal velocities of 2.22m in 2002/03 to 1.51m in 2005/06. This is in accordance to the behaviour of 12 other fast moving rock glaciers in the
Alps which show comparable dynamics since 2003.