Monitoring Glacial and Periglacial Environments in the Ortles-Cevedale (Eastern Italian Alps) Using the Sfm-Mvs Approach

Abstract:

In recent years, the development of a new photogrammetric technique, called Structure from Motion (SfM), has generated a great interest in the field of glaciology, as well as in glacial and periglacial geomorphology. This technique, coupled with dense image matching algorithms such as multi-view stereo (MVS), allows to obtain high resolution three-dimensional models of the surface employing sequences of overlapping images shot with common uncalibrated digital cameras.

This study investigates the potential of the SfM-MVS approach in reconstructing the surface of a glacier and a neighbouring rock glacier located in Alta Val de La Mare (Ortles-Cevedale, Eastern Italian Alps). The photos were taken from the ground using a consumer-grade SLR camera and processed using the computer vision-based software package Agisoft PhotoScan in order to generate the 3D models. A contemporaneous DTM surveyed by LiDAR provided high-resolution terrain information which was used to locate the GCPs needed to georeference the photogrammetric 3D model. The LiDAR DTM was also used as a reference for estimating the accuracy of the photogrammetric DTMs.

The results highlight that from a series of digital images taken from the ground it is possible to reconstruct the surface of both glaciers and rock glaciers, with good accuracy. The effectiveness of the photogrammetric method was also evaluated in light of the different substrata (fresh snow, old snow, firn, ice and debris) which were present at the moment of surveys, and of spatial characteristics as the distance from the camera and the terrain gradient.

The new digital photogrammetric methods proved to be well suited for low-budget research and application in remote areas, thus becoming potential alternatives to the efficient but also expensive and logistically-demanding LiDAR technologies for the evaluation of the glacier mass balance with the geodetic method, and for the assessment of the surface displacement of rock glaciers.