Open Session - SWISS GEOSCIENCE MEETINGs

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Symposium 6: Apply! Snow, ice and Permafrost Science + Geomorphology
databases (GLIMS, WGI) and observation programs (WGMS). GlobGlacier is one of ESAs data user element (DUE) activities that
responds to the needs of some major users groups, which are actively involved in defining the products and assessment of
the service (Volden, 2007).
The products that will be generated by GlobGlacier include (see Fig. 1): glacier outlines and terminus positions for 20'000
units each, snowlines and topographic information for 5000 units each, elevation changes for 1000 units and velocity fields
for 200 units. The techniques to be applied vary with the product and the sensor and include optical and microwave satellite
data as well as laser altimetry (cf. Paul et al., subm.). Glacier outlines will be derived from multispectral sensors (mainly
Landsat TM/ETM+) using well established methods (band ratios with threshold) combined with manual editing and GIS-based
data fusion at three different levels of detail: Level 0 (L0): outlines enclosing contiguous ice masses that are corrected for
misclassification (e.g. debris, shadow, water); L1: individual glaciers that result from combining L0 outlines with hydrologic
divides; L2: outlines from L1 combined with DEM data to obtain a detailed glacier inventory. The terminus position will be
marked where the central flowline crosses the glacier terminus. Snow lines will also be derived from optical imagery based
on terrain and atmospherically corrected albedo values. The topography information is basically derived from the freely
available SRTM DEM and complemented by DEMs from optical stereo sensors (e.g. ASTER, SPOT) and interferometric techniques
(e.g. using ERS1/2 SAR data) in regions outside the SRTM coverage. Elevation changes will be calculated by differencing
DEMs from two points in time and by comparing spot elevations from laser altimeters at orbit crossing points. Finally,
velocity fields will be derived from feature tracking of repeat pass optical imagery or from microwave sensors using differential
SAR interferometry or offset-tracking. The time period analysed will depend on the available satellite data and vary
from seasonal to annual means.
REFERENCES
GCOS 2006: Systematic Observation Requirements for Satellite-based Products for Climate - Supplemental details to the
satellite-based component of the Implementation Plan for the Global Observing System for Climate in Support of the
UNFCCC. GCOS Report 107, WMO/TD No. 1338, 103 pp.
IGOS 2007: Integrated Global Observing Strategy Cryosphere Theme Report - For the Monitoring of our Environment from
Space and from Earth. Geneva: World Meteorological Organization. WMO/TD-No. 1405. 100 pp.
Paul, F., A. Kääb, H. Rott, A. Shepherd, T. Strozzi, & E. Volden subm.: GlobGlacier: Mapping the worlds glaciers and ice caps
from space. Earsel eProceedings.
Volden, E. 2007: ESAs GlobGlacier project. In: CliC Ice and Climate News, Issue 9, 8.
Figure 1. Schematic overview of the workflow, the workpackages and the generated products of the GlobGlacier project.