Abstract
Unmanned Aerial Vehicles (UAV) are a rapidly evolving tool in geosciences and are increasingly deployed for studying the dynamic processes of the earth’s surface. To assess the potential of autonomous low-cost UAVs for the mapping and monitoring of alpine glaciers, we conducted multiple aerial surveys on the Kanderfirn in the Swiss Alps in 2017 and 2018 using open hardware and software of the Paparazzi UAV project. The open-source photogrammetry software OpenDroneMap was tested for the generation of high-resolution orthophotos and digital surface models (DSMs) from aerial imagery and cross-checked with the well-established proprietary software Pix4D. Accurately measured ground control points served for the determination of the geometric accuracy of the orthophotos and DSMs. A horizontal (xy) accuracy of 0.7–1.2 m and a vertical (z) accuracy of 0.7–2.1 m was achieved for OpenDroneMap, compared to a xy-accuracy of 0.3–0.5 m and a z-accuracy of 0.4–0.5 m obtained for Pix4D. Based on the analysis and comparison of different orthophotos and DSMs, surface elevation, roughness and brightness changes from 3 June to 29 September 2018 were quantified. While the brightness of the glacier surface decreased linearly over the ablation season, the surface roughness increased. The mean DSM-based elevation change across the glacier tongue was 8 m, overestimating the measured melting and surface lowering at the installed ablation stakes by about 1.5 m. The presented results highlight that self-built fixed-wing UAVs in tandem with open-source photogrammetry software are an affordable alternative to commercial remote-sensing platforms and proprietary software. The applied low-cost approach also provides great potential for other regions and geoscientific disciplines.
Highlights
Global climate change affects glaciers worldwide and has led to an increased ice mass loss in recent decades (e.g., [1,2])
The open-source photogrammetry software OpenDroneMap was tested for the generation of high-resolution orthophotos and digital surface models (DSMs) from aerial imagery and cross-checked with the well-established proprietary software Pix4D
Eight aerial surveys for the generation of high-resolution orthophotos and DSMs were successfully accomplished with the developed low-cost Unmanned Aerial Vehicles (UAV) at the Kanderfirn in 2017 and 2018 (Table 1)
Summary
Global climate change affects glaciers worldwide and has led to an increased ice mass loss in recent decades (e.g., [1,2]). For quantification of the ongoing ice mass loss and projection of future runoff regimes, monitoring and analysing spatiotemporal changes in the geometry, mass budget, dynamics and surface characteristics (albedo, roughness, debris thickness, etc.) of glaciers is fundamental. Before the era of satellite observations, glacier monitoring primarily relied on in-situ mass balance measurements at a few sites (e.g., [9,10]). To complement point measurements and study larger areas of the cryosphere, the application of satellite-based and airborne remote sensing data has become standard (e.g., [11,12]). To overcome some of the drawbacks related to satellite remote sensing, Unmanned
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