Abstract
Abstract. Snow depth mapping in Alpine forests is of high importance for hydrogeology, ecology, tourism, and natural hazards prevention. Different remote sensing approaches have been employed for the precise mapping of snow depth within forests. However, optical sensors cannot provide below-canopy information. While Airborne Laser Scanning (ALS) systems have been used successfully in this context and allow obtaining data below canopies, the costs of acquisitions are very high, not allowing frequent data acquisitions. UAV-based Lidar technology potentially can provide the critical below-canopy information at lower cost and allows for frequent acquisitions.First attempts to employ a UAV-based Lidar system in forests have proven promising, but they are limited to flat forests and to grid-level snow depth calculations. In this study, we present UAV-based Lidar data of both flat and steep forests. Different Lidar processing workflows are analyzed and compared, and snow depth algorithms are used both at the point and the grid level. Whereas the UAV-Lidar system proved capable of mapping snow in both environments, the steep forests' data processing comes with greater challenges, especially for the 3D registration, ground classification, and point-to-point snow depth calculations.
Highlights
IntroductionIn Alpine regions, the snow dynamics and the snowpack properties affect ecology (Wipf et al, 2009), water resources (Farinotti et al, 2012; Thornton et al, 2021) and are relevant for snowmelt forecasts and tourism (Pütz et al, 2011)
Forests cover around 30% of the surface of Switzerland
This study presented the first application of Unmanned Aerial Vehicle (UAV)-based lidar aimed at assessing its performance for mapping snow depth on flat versus sloped forested terrain
Summary
In Alpine regions, the snow dynamics and the snowpack properties affect ecology (Wipf et al, 2009), water resources (Farinotti et al, 2012; Thornton et al, 2021) and are relevant for snowmelt forecasts and tourism (Pütz et al, 2011). The challenges identified include accurate flight planning and the subsequent Lidar-related processing workflows These challenges are accentuated in steep forested terrain due to the difficulties of operating UAV in such terrain. Steep terrain typically leads to increased vertical inaccuracies for Lidar systems with larger laser beam footprints (Deems et al, 2013; Baltsavias et al, 1999) For this reason, UAV-based Lidar has the potential to
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