AUSTRIAN RESEARCH CENTRE FOR FORESTS (BFW) | DEPARTMENT OF NATURAL HAZARDS. HOFBURG RENNWEG 1 | 6020 INNSBRUCK | AUSTRIA.
Applying Terrestrial Laserscanning to Continuous Snow Cover Monitoring in an Alpine Environment – A Feasibility Study MARC S. ADAMS1, ANDREAS HUBER1 & THOMAS GIGELE1
Introduction
Study Site A Riegl LPM98-2K TLS was mounted in a weatherproof containment (Fig. I) in a ski area in Western Austria at 2260 m a.s.l., to monitor an avalanche slope (Fig. II). From 31 January to 5 June 2013 the TLS acquired 632 scans (covered area 34,000 m²; mean point spacing 0.4 - 1.1 m; accuracy ± 0.05 m (1σ) +≤ 20 ppm). A scanner control routine was developed and implemented for continuous automated remote TLS operation. Seven avalanche-blasting devices (‘Avalanche Master’), an avalanche mitigation measure (‘Snowcatcher’), a webcam and an automated weather station located in the area, were also utilised in this study.
Promptly available information on the spatial and temporal distribution of snow depth is essential to snow science and practice. While in-situ data collection of the snowpack is labour-intensive and potentially hazardous, close-range sensing techniques allow monitoring snow depth from a safe distance. One of the most powerful instruments in this context are Terrestrial Laser Scanners (TLS). They are able to generate high-resolution 3D point clouds, representing the snow surface. However, wintry conditions in (high-) alpine terrain, e.g. poor visibility due to snowfall, blowing snow or fog, can often interfere with TLS data collection or render it impossible.
Fig. I
Fig. II
ATLS Data Collection in Different Weather & Snow Conditions Sunny
Snowfall
Overcast
flowchart
Data from the automated TLS allows generating maps showing both absolute snow bla depth (Fig. III, snow depth on 1 Feb, 6 AM, 1.5 – 3.5 m); and relative snow depth (Fig. IV, snowbla depth change 1 Feb, 6 AM to 2 Feb, 7 PM; Fig. V, multiple small avalanche events on morning ofbla 4 June, 1 – 1.5 m fracture depth, 0.1 – 0.6 m deposit height). Fig. IV
Avalanche
Feasiblity of Automated TLS
Results: Snow Depth Maps
Fig. III
Fog
Fig. V
In summary, the results show, that despite the adverse weather conditions (e.g. temperatures below -20°C, high wind speeds and heavy snowfall), the instrument was fully functional for almost the entire measurement campaign. Of the 632 scans, 69% show a high quality (data could be retrieved for >90% of the measurements per scan), 24% are medium quality (9071%), 3% low quality (70-50%) and only 4% are not usable (
