Brief communication: 3-D reconstruction of a collapsed rock pillar from Web-retrieved images and terrestrial lidar data – the 2005 event of the west face of the Drus (Mont Blanc massif)

Abstract

Abstract. In June 2005, a series of major rockfall events completely wiped out the Bonatti Pillar located in the legendary Drus west face (Mont Blanc massif, France). Terrestrial lidar scans of the west face were acquired after this event, but no pre-event point cloud is available. Thus, in order to reconstruct the volume and the shape of the collapsed blocks, a 3-D model has been built using photogrammetry (structure-from-motion (SfM) algorithms) based on 30 pictures collected on the Web. All these pictures were taken between September 2003 and May 2005. We then reconstructed the shape and volume of the fallen compartment by comparing the SfM model with terrestrial lidar data acquired in October 2005 and November 2011. The volume is calculated to 292 680 m 3 (±5.6 %). This result is close to the value previously assessed by Ravanel and Deline (2008) for this same rock avalanche (265 000 ± 10 000 m 3 ). The difference between these two estimations can be explained by the rounded shape of the volume determined by photogrammetry, which may lead to a volume overestimation. However it is not excluded that the volume calculated by Ravanel and Deline (2008) is slightly underestimated, the thickness of the blocks having been assessed manually from historical photographs.

Paraglacial Rock Slope Adjustment Beneath a High Mountain Infrastructure—The Pilatte Hut Case Study (Écrins Mountain Range, France)

“…This method has recently become popular (Kappas, 2011;Marcer et al, 2017b;Vargo et al, 2017;Fugazza et al, 2018). Some other studies have combined terrestrial photogrammetry and TLS data for the reconstruction of detached rock volumes in high mountain environments (Curtaz et al, 2014;Guerin et al, 2017).…”

“…The workflow described by Smith et al (2016) and applied by Guerin et al (2017) was used to generate point clouds of the glacier and the rockwall beneath the hut for different years with Agisoft PhotoScan 1.2.6. and aerial photos obtained from the Institut Géographique National (IGN) for the period 1960-2009. The different steps of the workflow are summed up in Figure 4.…”

Pros and Cons of Structure for Motion Embarked on a Vehicle to Survey Slopes along Transportation Lines Using 3D Georeferenced and Coloured Point Clouds

“…and their evolution over time by comparing 3D point clouds acquired at different time steps [19][20][21]. Thus, LiDAR [22][23][24] and photogrammetrically derived point clouds [25][26][27][28][29] are used to monitor slope evolution.…”

Using street view imagery for 3-D survey of rock slope failures

“…and its evolution over time by comparing 3-D point clouds acquired at different time steps. For example, 3-D remote sensing techniques are helping to better quantify key aspects of rock slope evolution, including the accurate quantification of rockfall rates and the deformation of rock slopes before failure using both lidar (Rosser et al, 2005;Oppikofer et al, 2009;Royan et al, 2014;Kromer et al, 2015;Fey and Wichmann., 2017) and photogrammetrically derived point clouds (Walstra et al, 2007;Lucieer et al, 2013, Stumpf et al, 2015Fernandes et al, 2016;Guerin et al, 2017;Ruggles et al, 2016).…”

“…Snavely et al, 2008;Guerin et al, 2017). Some of the largest sources of pictures online are street view imagery (SVI) services, which offer 360 • panoramas from many roads, streets and other places around the world (Anguelov et al, 2013).…”