Photogrammetric reconstruction and multi-temporal comparison of Brenva glacier (Italy) from archive photos

Since climate change has a significant impact on glaciers, it is essential to track their morphological change by identifying variations in ice mass. In combination with modern photogrammetric approaches, such as Structure-from-Motion (SfM) and Multi-View-Stereo (MVS) dense matching, historical aerial photographs may offer useful information for this objective. Point clouds of the 3D surface of the glaciers may be used to track changes in thickness and height during years. By using appropriate methods for calculating the distances between pairs of point clouds, this operation may be completed. Here, an Alpine glacier massif on Mount Blanc in the Italian Alps was chosen as the case study. National Geographic and the Forestry Institute of France (IGNF) provided seven data sets of digitized analog aerial photos. These were chosen, downloaded, and utilized for photogrammetric analysis. These data sets span almost 40 years, from 1967 to 2006, in total. While the change in ice thickness of these glaciers was relatively small until the mid-1990s, this study revealed an increasing reduction rate at the beginning of 21st century. This paper describes the adopted methodological approach for photogrammetric reconstruction, quality assessment and point cloud comparison. One of the two major glaciers in the considered group (Brenva Glacier) has been focused in this paper as case study.