Local and General Monitoring of Forni Glacier (Italian Alps) Using Multi-Platform Structure-From-Motion Photogrammetry

Abstract

ABSTRACT:Experts from the University of Milan have been investigating Forni Glacier in the Italian alps for decades, resulting in the archive of a cumbersome mass of observed data. While the analysis of archive maps, medium resolution satellite images and DEM's may provide an overview of the long-term processes, the application of close-range sensing techniques offers the unprecedented opportunity to operate a 4D reconstruction of the glacier geometry at both global and local levels. In the latest years the availability of high-resolution DEM's from stereo-photogrammetry (2007) and UAV-photogrammetry (2014 and has allowed an improved analysis of the glacier ice-mass balance within time. During summer 2016 a methodology to record the local disruption processes has been investigated. The presence of vertical and sub-vertical surfaces has motivated the use of Structure-from-Motion Photogrammetry from ground-based stations, which yielded results comparable to the ones achieved using a long-range terrestrial laser scanner. This technique may be assumed as benchmarking for accuracy assessment, but is more difficult to be operated in high-mountain areas. Nevertheless, the measurement of GCP's for the terrestrial photogrammetric project has revealed to be a complex task, involving the need of a total station a GNSS. The effect of network geometry on the final output has also been investigated for SfM-Photogrammetry, considering the severe limitations implied in the Alpine environment.

Monitoring Alpine Glaciers From Close-Range to Satellite Sensors

“…Such kind of targets (about 7-10 per campaign) could be clearly recognized in images from drone, but not in terrestrial photos. After trying solutions based on total station measurements of another set of GCPs for terrestrial blocks (see Scaioni et al, 2017) or trying to directly determine the position of camera stations using GNSS as proposed in Forlani et al (2015), we abandoned these approaches because too much involved to handle in the glacier environment. Thus, the georeferencing of each "terrestrial" point cloud has been done by the co-registration to the contemporary point cloud obtained from drone photogrammetry.…”

Integration of Terrestrial and Uav Photogrammetry for the Assessment of Collapse Risk in Alpine Glaciers

“…Given a suitable geodetic reference, multi-platforms surveys may be integrated to obtain full 3D models which completely depict geomorphic objects under different point of views. A review on the application of photogrammetry to the study of Alpine glaciers can be found in Fugazza et al (2017) and Scaioni et al (2017). This paper would like to describe the acquisition and processing steps of two data sets aimed at mapping risk on the surface of Forni Glacier.…”

“…Since 2007, several high-resolution DSMs have been derived to witness the dynamic evolution of the terminus tongue of Forni Glacier. While a more detailed description can be found in Scaioni et al (2017), here we limit to give a short mention.…”

“…All photogrammetric blocks (2016 and 2017) were processed using a similar pipeline based on SfM photogrammetry. While more technical details on the standard workflow and on quality assessment issues may be found in Scaioni et al (2017), here we would like to highlight some specific problems as well to show some new results coming from the survey carried out on September 2017.…”

Technical Aspects Related to the Application of SFM Photogrammetry in High Mountain

“…1. In Scaioni et al (2017a) a discussion is reported whether is better to acquire more images with shorter baselines, or less images with longer baselines and a more regular geometry. The proposed solution is to capture a larger number of images with shorter baselines, since the number of points in the final point cloud is proportional to the number of employed image; 2.…”