Frank Paul
Department of Geography, University of Zurich
Using Sentinel-2 MSI for
global-scale glacier mapping
What we need and what we have
• Freely available multispectral satellite data covering glaciers
• acquired at the end of the ablation season (without clouds and seasonal snow)
• a band in the SWIR (1.5 mm) for automated classification of clean ice
• sufficient spatial resolution (10-30 m) to identify the target and repetition
• experts performing the processing and applying corrections scene-by-scene
• Satellites and DEMs being applied
• Landsat (MSS/TM: archive & change assessment, ETM+/OLI: ongoing)
• ASTER (end of life), SPOT (expensive), S2a/b (forthcoming)
• SRTM/GDEM-2 (widely used, artefacts), GIMP (Greenland), WorldDEM (future)
• A first version of a globally complete glacier inventory (RGI)
• required: quality improvement, temporal consistency, change assessment
• mapping guidelines for the community, RGI/GLIMS integration
• long-term strategy for an operational service (fast changes, personnel costs)
Comparing S-2 MSI with Landsat OLI
ESA 2012
L8-OLI S2-MSI win
Coverage 180 km 100 km O
Revisit 16 10 / 5 M
SWIR band yes yes O/M
Resolution 30 m 10/20 m M
Operational yes no O
Orthorectific. GLS2000 ? ?
12-bit bands yes yes O/M
• Key improvements
• spatial resolution (debris,
mapping at 10 m, velocity)
• revisit period (seasonal snow, in
some regions >20 years waiting)
• 12-bit: better discrimination of
snow facies but ratio less good
Flow velocity and DEM accuracy
Mean annaual flow velocity
Heid & Kääb (2012)
Feature tracking (3 yr difference)
The LASER band: snow grain size mapping
Maximum change of spectral reflectance at 1065 nm,
which is where LASERs of ICESat and ALS are working
Snow grain size dependence
A related band would be nice to have in the future
Summary
• Current global scale glacier mapping relies on Landsat 8 OLI
and some ASTER / ETM+ (still 30 m but huge TM archive)
• Sentinel 2 will help closing the acquisition gap (temporal) and
getting more cloud-free coverage without seasonal snow
• The higher spatial resolution of S-2 MSI compared to L8-OLI
will improve the quality of the outlines (clean ice) as well as
identification of debris covered ice
• Also creation of glacier velocity fields from feature tacking
will be considerably improved by the 10 m resolution
• The DEM used for orthorectification needs to be better than
SRTM &GDEM2 (and publicly available => drainage divides)
• The 100 km tiling seems suboptimal for glacier mapping