Assessing the applicability of terrestrial laser scanning for spatial snow depth measurements

Snow depth observation in potentially dangerous avalanche-starting zones is important for avalanche prediction and dimensioning of permanent protection measures. The possible danger of avalanches complicates measurements of snow depth in the field (e.g. by probing). Therefore, the applicability of terrestrial laser scanning to measure the depth of the snow cover was analysed. Different long-range laser profile measuring systems were used carrying out numerous field campaigns (Vorarlberg, Austrian Alps). The objective of the study was to discover under which meteorological and snowpack conditions the measurements must be taken in order to provide accurate results (< 10 cm). For the first time a detailed investigation focusing on the limitations and properties of different terrestrial laser scanning systems for application in snow and avalanche research is presented and discussed. Results suggest that under adequate measurement conditions the distance between the scanner position and the surface of the snowpack can be measured with an accuracy < 10 cm. Poor weather conditions such as snowfall or fog preclude the collection of reliable data. If the snow surface was wet and the snow grain size was large (> 1 mm) only 50% of the emitted signal was received, depending on the angle of incidence. In any case, the accuracy decreases with increasing distance to the target. For distances to the object of more than about 500 m, the accuracy that can be achieved with the used TLS measuring systems is rather low and the errors can be significantly larger than 10 cm.