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Open AccessArticle

On the Automated Mapping of Snow Cover on Glaciers and Calculation of Snow Line Altitudes from Multi-Temporal Landsat Data

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Department of Geography, University of Zurich, 8057 Zurich, Switzerland
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Department of Atmospheric and Cryospheric Sciences, University of Innsbruck, 6020 Innsbruck, Austria
3
Department of Geography and Regional Science, University of Graz, 8010 Graz, Austria
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Institute of Applied Remote Sensing (EURAC), 39100 Bozen/Bolzano, Italy
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Institute of Geography, University of Innsbruck, 6020 Innsbruck, Austria
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ENVEO IT GmbH, Fürstenweg 176, 6020 Innsbruck, Austria
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(12), 1410; https://doi.org/10.3390/rs11121410
Received: 17 April 2019 / Revised: 29 May 2019 / Accepted: 7 June 2019 / Published: 14 June 2019
(This article belongs to the Special Issue Remote Sensing of Glaciers at Global and Regional Scales)
Mapping snow cover (SC) on glaciers at the end of the ablation period provides a possibility to rapidly obtain a proxy for their equilibrium line altitude (ELA) which in turn is a metric for the mass balance. Satellite determination of glacier snow cover, derived over large regions, can reveal its spatial variability and temporal trends. Accordingly, snow mapping on glaciers has been widely applied using several satellite sensors. However, as glacier ice originates from compressed snow, both have very similar spectral properties and standard methods to map snow struggle to distinguish snow on glaciers. Hence, most studies applied manual delineation of snow extent on glaciers. Here we present an automated tool, named ‘ASMAG’ (automated snow mapping on glaciers), to map SC on glaciers and derive the related snow line altitude (SLA) for individual glaciers using multi-temporal Landsat satellite imagery and a digital elevation model (DEM). The method has been developed using the example of the Ötztal Alps, where an evaluation of the method is possible using field-based observations of the annual equilibrium line altitude (ELA) and the accumulation area ratio (AAR) measured for three glaciers for more than 30 years. The tool automatically selects a threshold to map snow on glaciers and robustly calculates the SLA based on the frequency distribution of elevation bins with more than 50% SC. The accuracy of the SC mapping was about 90% and the SLA was determined successfully in 80% of all cases with a mean uncertainty of ±19 m. When cloud-free scenes close to the date of the highest snowline are available, a good to very good agreement of SC ratios (SCR)/SLA with field data of AAR/ELA are obtained, otherwise values are systematically higher/lower as useful images were often acquired too early in the summer season. However, glacier specific differences are still well captured. Snow mapping on glaciers is impeded by clouds and their shadows or when fresh snow is covering the glaciers, so that more frequent image acquisitions (as now provided by Sentinel-2) would improve results. View Full-Text
Keywords: Landsat; snow mapping; glacier; snow-covered area; mass balance; snow line altitude; equilibrium line altitude; multi-temporal analysis; digital elevation model Landsat; snow mapping; glacier; snow-covered area; mass balance; snow line altitude; equilibrium line altitude; multi-temporal analysis; digital elevation model
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MDPI and ACS Style

Rastner, P.; Prinz, R.; Notarnicola, C.; Nicholson, L.; Sailer, R.; Schwaizer, G.; Paul, F. On the Automated Mapping of Snow Cover on Glaciers and Calculation of Snow Line Altitudes from Multi-Temporal Landsat Data. Remote Sens. 2019, 11, 1410.

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