Monitoring temperate glacier activity has become
more and more necessary for economical and security reasons
and as an indicator of the local effects of global climate change.
Remote sensing data provide useful information on such complex
geophysical objects, but they require specific processing tech-
niques to cope with the difficult context of moving and changing
features in high-relief areas. This paper presents the first results
of a project involving four laboratories developing and combining
specific methods to extract information from optical and synthetic
aperture radar (SAR) data. Two different information sources are
processed, namely: 1) airborne photography and 2) spaceborne
C-band SAR interferometry. The difficulties and limitations of
their processing in the context of Alpine glaciers are discussed
and illustrated on two glaciers located in the Mont-Blanc area.
The results obtained by aerial triangulation techniques provide
digital terrain models with an accuracy that is better than 30 cm,
which is compatible with the computation of volume balance
and useful for precise georeferencing and slope measurement
updating. The results obtained by SAR differential interferometry
using European Remote Sensing Satellite images show that it is
possible to measure temperate glacier surface velocity fields from
October to April in one-day interferograms with approximately
20-m ground sampling. This allows to derive ice surface strain
rate fields required to model the glacier flow. These different
measurements are complementary to results obtained during the
summer from satellite optical data and ground measurements that
are available only in few accessible points. |
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