Spatially continuous mapping of snow depth in high alpine catchments using digital photogrammetry

Abstract

Information on snow depth and its spatial distribution is crucial for numerous applications in snow and avalanche research as well as in hydrology and ecology. Today, snow depth distributions are usually estimated using point measurements performed by automated weather stations and obsevers in the field combined with interpolation algorithms. However, these methodologies are not able to capture the high spatial variability of the snow depth distribution present in alpine terrain. Continuous and accurate snow depth mapping has been successfully performed using laser scanning but this methods can only cover limited areas and is expensive. We use the airborne ADS80 optoelectronic scanner, aquriring stereo imagery with 0.25 m spatial resolution to derive digital surface models o winter and summer terrains in the nighborhoood of Davos, Switzerland. The DSMs are generated using photogrammetric image correction techniques based on the multispectral nadir and backward-looking sensor data. In order to assess the accuracy of hte photogrammetric products, we compare these products with the following independedt data sete aquired simulataneously: (a) manually measured snow depth plots; (b) differental Global Navigation Satellite System (dGNSS) points; (c) terrestrial laser scanning (TLS); and (d) ground-penetrating radar (GPR) datasets. We demonstrate that the tethod presented can be used to map now depth at 2 m resolution with a vertical depth accuracy of 30 cm in the complex topography of the Apls. The snow depth maps presented have an average accuracy that is better than 15 % compared to the average snow depth of 2.2 m over the entire test site.