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Software News

13.03.2007 15:47 Age: 13 Jahre

Unstable slopes

Figure 1

Figure 2

Figure 3

Figure 4

Figures 1-4 show differential interferograms around the Grosse Aletsch glacier in Wallis (Switzerland) from JERS-1 SAR and ALOS PALSAR. Line-of-sight direction is from east-southeast (descending orbit), incidence angle is about 38 degrees, image width is 9 km. Background image is a shaded relief of the DEM.

Retreat of the Grosse Aletsch glacier in Wallis (Switzerland) resulted in the formation of a rockslide. The displacement in the slant-range direction in about three years between 1993 and 1996 measured with JERS-1 SAR was about 12 cm (i.e. one phase cycle). ALOS PALSAR data in the summer of 2006 indicated an increase of displacement in the slant-range direction to about 8 cm in 138 days. Also visible in the JERS-1 SAR interferogram of 21st June to 17th September 1996 and in the ALOS PALSAR interferogram of 13th September to 29th October 2006 are signals related to the displacement of active rock glaciers. In the other two interferograms phase decorrelation is observed at high altitudes because of the presence of snow cover. In the ALOS PALSAR interferograms signals are visible also at the border of Grosse Aletsch glacier. The rapid retreat of the glacier in the last years has changed significantly the topography. The use of an aged DEM for topographic phase removal lead to these uncompensated effects.

PALSAR is the L-Band SAR system on the recently launched Japanese ALOS satellite.
Support ESA DUE SLAM and GMES TERRAFIRMA . JERS SAR data courtesy J-2RI-001, ALOS PALSAR data courtesy P1750001, © JAXA, processing Gamma Remote Sensing. DHM25 © 2003 swisstopo.