Swiss Federal Institute for Forest, Snow and Landscape Research WSL

Avalanche bulletin and snow situation
Edition: Thu 20.3., 17:00
Avalanche Bulletin

Catchment scale snow depth mapping in high-alpine regions using digital photogrammetry

Project lead

Yves Bühler

Deputy

Andreas Stoffel

Project staff

Christian Ginzler
Mauro Marty
Lucie Anne Eberhard

Project duration

2010 - 2030

Cooperation Financing
Fig.1 High alpine terrain in the area of Davos

Information on snow depth and its spatial distribution in high-alpine catchments is crucial for many research topics and applications such as avalanche research, hydrology, snow and mountain ecology. Nowadays snow depth values are measured at point locations such as automatic weather stations or from observers in the field and are consequently interpolated to get an estimate of large scale snow depth. Several studies report a high spatial variability of snow depth and other snow pack parameters in mountainous regions, which cannot be reproduced by point measurements. Optical stereo data from different platforms offer a very attractive alternative to derive 3D surface data. Compared to laser scanning, photogrammetry is more economic and with the application of unmanned aerial systems (UAS) also more flexible (Bühler et al. 2016).

Airplane-based surveying sensors

Recent developments of sensor- and software technology for digital photogrammetry enable the generation of high spatial resolution digital surface models (DSMs) from airborne digital imagery even in high alpine regions and over snow-covered surfaces.

For this project, digital imagery from the Leica ADS80 (2010-2013) and ADS100  (2014-2017) opto-electronic scanners for a test site near Davos (145 km2) are used to derive high spatial resolution digital surface models by applying a highly automated workflow. The spatial resolution of the imagery is ~0.25 m (ADS80) and ~0.18 m (ADS100) and the radiometric resolution 12 bit (both). For the dense image matching the spectral bands in the near infrared (), red() and green() part of the electromagnetic spectrum are used.

From winter 2017 we switched to the professional Vexcel frame camera Ultracam X (2017) and then to the Ultracam Eagle M3 (2018 - today). With this state-of-the-art survey camera we were able to improve the ground sampling distance GSD to 0.1 - 0.15 m resulting in higher resolved snow depth maps (0.5 m) as well as higher accuracies.

Snow depth maps are calculated as the difference between the winter DSM and a snow-free summer DSM, whereby trees/shrubs, buildings and other infrastructure are masked out. One of the main challenges to derive good quality snow depth maps is the absolute orientation of the ADS stereo imagery, especially in winter due to the limited numbers of usable ground control points in a snow covered landscape.

Fig 2. Area east of Jackobshorn in the Dischma Valley. From upper left to lower right: Snowmap, shaded DSM, summer and winter Orthoimage

Products and accuracies

These results demsonstrate the feasibility of digital photogrammetry to map snow depth and its high spatial variability in alpine catchments. Until now the derived photogrammetric snow depth maps have already been used in different topics in other WSL/SLF groups like the investigation of the dependency of snow depth on elevation (Grünelwald et al. 2014), the parametrization of fractional snow covered area over complex topography (Helbig et al. 2021), the scaling of precipitation input to distributed hydrological models (Vögeli et al. 2016) and in particular for the validation of new, satellite-based snow depth models (Leiterer et al. 2020). The datasets are currently used for various further investigations at WSL/SLF.

Snow depth maps were acquired for the following dates:

Acquisition date Sensor Snow depth accuracy [RMSE] Spatial map resolution 
16.04.2010 ADS40 0.35 m 2 m
20.03.2012 ADS80 SH52 0.35 m 2 m
15.04.2013 ADS80 SH52 0.35 m 2 m
17.04.2014 ADS80 SH52 0.35 m 2 m
15.04.2015 ADS100 0.30 m 2 m

26.01.2016, 

09.03.2016, 

20.04.2016

 ADS100 0.3 m 2 m
16.03.2017 Ultracam X 0.25 m 0.5 m
11.04.2018 Ultracam Eagle M3 0.15 m 0.5 m
16.03.2019 Ultracam Eagle M3 0.15 m 0.5 m
06.04.2020 Ultracam Eagle M3 0.15 m 0.5 m
16.04.2021 Ultracam Eagle M3 0.15 m 0.5 m
23. 03. 2022 Ultracam Eagle M3 0.15 m 0.5 m
22. 03. 2023 Ultracam Eagle M3 0.15 m 0.5 m
Fig 3: Ultracam snow depth maps of the southern Dischma valley. In winter 2021 there is significantly more snow than in winter 2020. (map source: Federal Office of Topography)

Publications

Bührle L.J., Marty M., Eberhard L.A., Stoffel A., Hafner E.D., Bühler Y. (2023) Spatially continuous snow depth mapping by aeroplane photogrammetry for annual peak of winter from 2017 to 2021 in open areas. Cryosphere. 17(8), 3383-3408. https://doi.org/10.5194/tc-17-3383-2023 Institutional Repository DORA

Caye Daudt R., Wulf H., Hafner E.D., Bühler Y., Schindler K., Wegner J.D. (2023) Snow depth estimation at country-scale with high spatial and temporal resolution. ISPRS J. Photogramm. Remote Sens. 197, 105-121. https://doi.org/10.1016/j.isprsjprs.2023.01.017 Institutional Repository DORA

Bühler Y., Stoffel A., Eberhard L., Bührle L. (2023) Fotogrammetrische Schneehöhenkartierung aus Drohnen-, Flugzeug­- und Satellitenbildern. In Eidg. Forschungsanstalt für Wald, Schnee und Landschaft, WSL (Ed.), WSL Berichte: Vol. 134. Neue Fernerkundungs­technologien für die Umweltforschung und Praxis. Birmensdorf: Eidg. Forschungsanstalt für Wald, Schnee und Landschaft, WSL. 61-66. https://doi.org/10.55419/wsl:33072 Institutional Repository DORA

Bühler Y., Marty M., Egli L., Veitinger J., Jonas T., Thee P., Ginzler C. (2015) Snow depth mapping in high-alpine catchments using digital photogrammetry. Cryosphere. 9(1), 229-243. https://doi.org/10.5194/tc-9-229-2015 Institutional Repository DORA

Eberhard L.A., Sirguey P., Miller A., Marty M., Schindler K., Stoffel A., Bühler Y. (2021) Intercomparison of photogrammetric platforms for spatially continuous snow depth mapping. Cryosphere. 15(1), 69-94. https://doi.org/10.5194/tc-15-69-2021 Institutional Repository DORA

Bühler Y., Bührle L., Eberhard L., Marty M., Stoffel A. (2021) Grossflächige Schneehöhen-Kartierung mit Flugzeug und Satellit. Geomat. Schweiz. 119(9-10), 212-215. Institutional Repository DORA

Helbig N., Bühler Y., Eberhard L., Deschamps-Berger C., Gascoin S., Dumont M., … Jonas T. (2021) Fractional snow-covered area: scale-independent peak of winter parameterization. Cryosphere. 15(2), 615-632. https://doi.org/10.5194/tc-15-615-2021 Institutional Repository DORA

Leiterer R., Wulf H., Milani G., Sassik B., Bühler Y., Wegner J.D. (2020) Schneekartierung aus dem All - das Potenzial frei verfügbarer Satellitendaten. Wasser Energ. Luft. 112(3), 171-174. Institutional Repository DORA

Noetzli C., Bühler Y., Lorenzi D., Stoffel A., Rohrer M. (2019) Schneedecke als Wasserspeicher. Drohnen können helfen, die Abschätzungen der Schneereserven zu verbessern. Wasser Energ. Luft. 111(3), 153-157. Institutional Repository DORA

Bühler Y., Adams M.S., Stoffel A., Boesch R. (2017) Photogrammetric reconstruction of homogenous snow surfaces in alpine terrain applying near-infrared UAS imagery. Int. J. Remote Sens. 38(8-10), 3135-3158. https://doi.org/10.1080/01431161.2016.1275060 Institutional Repository DORA

Bühler Y., Adams M.S., Bösch R., Stoffel A. (2016) Mapping snow depth in alpine terrain with unmanned aerial systems (UASs): potential and limitations. Cryosphere. 10(3), 1075-1088. https://doi.org/10.5194/tc-10-1075-2016 Institutional Repository DORA

Bühler Y., Stoffel A., Eberhard L., Feuerstein G.C., Lurati D., Guler A., Margreth S. (2018) Drohneneinsatz für die Kartierung der Schneehöhenverteilung. Bündnerwald. 71(8), 20-24. Institutional Repository DORA

Grünewald T., Bühler Y., Lehning M. (2014) Elevation dependency of mountain snow depth. Cryosphere. 8(6), 2381-2394. https://doi.org/10.5194/tc-8-2381-2014 Institutional Repository DORA

Boesch R., Bühler Y., Marty M., Ginzler C. (2016) Comparison of digital surface models for snow depth mapping with UAV and aerial cameras. In L. Halounova, V. Šafář, P. L. N. Raju, L. Plánka, V. Ždímal, T. Srinivasa Kumar, … Q. Weng (Eds.), The international archives of the photogrammetry, remote sensing and spatial information sciences: Vol. XLI-B8. XXIII ISPRS congress, commission VIII. Gottingen, Germany: Copernicus. 453-458. https://doi.org/10.5194/isprs-archives-XLI-B8-453-2016 Institutional Repository DORA

Adams M.S., Bühler Y., Fromm R. (2017) Multitemporal accuracy and precision assessment of unmanned aerial system photogrammetry for slope-scale snow depth maps in alpine terrain. Pure Appl. Geophys. 175(9), 3303-3324. https://doi.org/10.1007/s00024-017-1748-y Institutional Repository DORA

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