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How Drone Surveying and ShapeMetriX Captured a 200-Metre Rockfall in the Alps  

When a major rockfall occurs, the first challenge is often getting close enough to assess the damage. In mountainous regions like Austria’s Alps, where vertical rock faces loom above roads, trails, and tourist facilities, unstable slopes are often too dangerous to access on foot. 

To safely evaluate these sites, engineers are increasingly turning to drone photogrammetry and ShapeMetriX, our software that models and assesses rock masses, terrain, and excavation surfaces, for remote site inspections. This combination enables fast, high-resolution data capture and detailed 3D modelling — all without putting personnel at risk. Here, we’ll cover how this approach was used to assess a cliff collapse in the Alps from a safe vantage point. 

A Collapse in a High-Risk Zone 

In the month of December, following cycles of daytime thawing and nighttime freezing, several large blocks — some measuring several cubic metres — detached from a 200 m-high rock wall in an uninhabited recreational area. The detached material crashed near holiday sheds and a public swimming bath, prompting urgent calls for assessment in a zone still too unstable to access on foot. 

Figure 1. A 200 m-high rock wall in Austria suffered a December rockfall (left). Drone-based data collection allowed engineers to assess the site remotely (right). 

Inaccessible Terrain and Time-Sensitive Decisions 

Traditional mapping methods were out of the question due to the risk of further collapse and no safe access for field mapping. Yet decision-makers still needed critical information on the geological conditions for the assessment and initiation of measure and need to gather data on rock structures where nobody could safely stand. 

Capturing the Rock Wall From a Safe Distance 

To solve this, engineers deployed a DJI M600 drone equipped with a 36.3 MP Sony ILCE 7R camera. The drone was flown manually in “interactive mode” under the guidance of a geologist who directed the pilot toward key structural features. Maintaining a 20–30 m offset from the wall, the drone captured oblique images at optimal angles for photogrammetric reconstruction. 

Over the course of several missions, the drone collected over 700 high-resolution images. With photos taken every 2 seconds, the team ensured high redundancy — each area of interest was imaged at least five times from different viewpoints. In total, the drone covered more than 30 hectares of steep terrain in just 75 minutes of flight time, achieving a ground sample distance (GSD) of approximately 1 cm/pixel. 

Figure 2. Point cloud and location of 740 images captured during drone flights. Irregular spacing reflects manual flight adjustments targeting geological features. 

A Detailed 3D Model Ready in Hours 

In under three hours, the image set was processed into a textured 3D surface mesh using ShapeMetriX, that had a 12-million-point 3D model revealing joint planes, failure surfaces, and even a 2,350 m³ unstable block (Figure 4). Even without ground control points, GPS-referenced imagery proved accurate enough for structural analysis. 

Figure 3. Photogrammetric 3D surface model of the rockfall site, generated from drone imagery shortly after the event. Freshly exposed rock surfaces in the upper zone indicate the primary failure area. 

The model revealed zones of recent failure along with clearly defined joint planes and block separations. Engineers were able to perform digital geologic mapping, calculate joint set orientations, and even estimate the volume of potentially unstable blocks. 

Figure 4. Volume estimation of an unstable block (>65 m high) conducted directly in the model: 2,350 m³. 

When Safety and Detail Can’t Be Compromised 

This case shows that drone-based photogrammetry is a powerful solution for high-risk geotechnical sites. ShapeMetriX provided a detailed and measurable 3D model of an inaccessible rock wall within hours, allowing engineers to make confident decisions quickly and safely. 

For teams working in mountainous terrain, or any environment where physical access is limited, UAV-based modelling tools offer more than just a view from above — they offer full-scale, data-rich replicas of the terrain that can be measured, monitored, and archived over time. 

Even More Possibilities With the Rocscience Software Suite 

ShapeMetriX streamlines geotechnical analysis by converting image and LIDAR data into accurate 3D models of rock surfaces, and now it seamlessly integrates with Rocscience tools for deeper stability assessments: 

  • Dips: Import discontinuity orientation data directly from ShapeMetriX for stereonet plotting, kinematic analysis, and structural interpretation. 
  • RocSlope2: Use ShapeMetriX data to perform wedge, planar, and toppling failure analysis in 2D, complete with sensitivity testing and stabilization design. 
  • RocSlope3: Transfer 3D discontinuity geometry into RocSlope3 for probabilistic and deterministic analysis of complex rock slopes. 

Try ShapeMetriX for Your Next Project 

If you need fast, reliable models from hard-to-reach sites, drone surveying with ShapeMetriX can deliver. Start your free trial and take your next slope analysis airborne.  

Source: A. Gaich, M- Pötsch, B- Rieder, W. Schubert. 2019. Drone imagery for the acquisition and assessment of rock fall areas. In: ISRM Congress 2019 Proceedings – Int’l Symposium on Rock Mechanics, Iguassu, Brazil, Paper 15036.