Monitoring of high alpine mass movements combining laser scanning with digital airborne photogrammetry

• Creep rates can be obtained between an orthophoto and a laser scanned DEM.
• Automatic post-processing eliminates erroneous creep vectors and indicates accuracy.
• A high pass filtered DEM is better than an illuminated DEM for defining creep.
• An accuracy analysis is presented taking into account the spatial extent of movement.
• Differential creep in steep terrain forms ridges and furrows on rock glaciers.

Airborne- and terrestrial laser scanning are used in combination with digital airborne photogrammetry to monitor surface changes between 2009 and 2011 on rock glaciers and landslides at three mountain permafrost sites (Grabengufer, Schafberg and Flüela Pass) in the Swiss Alps. 3D surface changes detected through comparison of multitemporal laser scanning data, as well as horizontal creep rates determined using laser scanning data and digital airborne photogrammetry are analyzed. The methods applied allow comprehensive quantification of mass movements and volumetric changes, which are presented in 2.5D. GPS ground truths are used as reference data at the Grabengufer site. On the basis of this, a quality estimation is developed for the sites without GPS reference data. For changes with an extent of about 25 m2, a level of significance of 3 cm was obtained for both horizontal and vertical displacements under optimal measurement conditions. The complex dynamics of creeping and sliding permafrost features are investigated through analysis of their surface kinematics.