Abstract
Abstract. Precise and accurate three-dimensional geospatial data has become increasingly available thanks to advances in both Terrestrial Laser Scanning (TLS) and Structure-from-Motion Photogrammetry (SfM). These tools provide valuable information for mapping geomorphological features and detect surface changes in mountainous environments. The exploitation of 3D point-clouds has been proven tremendously useful in the field of geosciences. It remains, however, controversial whether cost efficient photogrammetry can provide as accurate and reliable geospatial information as the significantly more expensive laser scanning or not. In this study, a rockfall case site in the territory of Obergurgl, Austria, is investigated in order to provide answers to the above question in a complex environment. The analysis includes different terrestrial photogrammetry configurations aiming to comprehensively define the strengths and limitations of terrestrial photogrammetry over TLS. The latter constitutes an optimized methodology that provides guidelines for costly future assessments as part of the site investigation phase in geohazard management. There are no doubts that compared to traditional and conventional surveying methods TLS and Photogrammetry both offer products much faster and with a much higher data density. In the current study, we show that when photogrammetry is applied following a well-defined optimized strategy, it can be potentially an adequate alternative to more costly TLS datasets for mass movement assessment and monitoring purposes.
Highlights
Landslides and rock failures in mountainous environments have serious and dramatic impacts on society and infrastructure, often leading to fatal situations, especially in the Alpine terrain, where high touristic activity takes place throughout the year
Results show that our procedure provides a reliable tool for detailed point-cloud assessment, and facilitates the usage of photogrammetric based 3D data to monitor rockfall phenomena at low costs
The latter causes problems such as Ground Control Points (GCPs) establishment which comprises a common issue in geoscience domain while working in mountainous environments
Summary
Landslides and rock failures in mountainous environments have serious and dramatic impacts on society and infrastructure, often leading to fatal situations, especially in the Alpine terrain, where high touristic activity takes place throughout the year. Terrestrial laser scanner (TLS) point-clouds have become a common practice to describe, monitor or characterize earth surface processes (Sack, Orme, 2013; Telling et al 2017) Their cost, maintenance, and operation may prove cumbersome and require wide resources, especially as surveys must be repeated for the study of dynamic processes (e.g., landslides, rockfalls, rock glaciers, etc.). The quality of the multi-epoch point-clouds may deteriorate and introduce biases and artefacts into the monitoring process Assessing these failures and enable the cheaper usage of such technique (SfM), is a keystone for improving the suitability of photogrammetric techniques for both research and professionals. We investigated an active mass movement and propose a quality assessment procedure for multi-epoch point-clouds in complex environment while testing acquisition and processing parameters of the photogrammetric point-clouds for geomorphological monitoring. Identifying morphological changes in hazardous areas is an important task for local and regional protection authorities
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