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Titel |
Monitoring glaciers and indications of subglacial volcanic activity using small-scale Top-Hat reflectors - An IsViews experiment on Myrdalsjökull, Iceland |
VerfasserIn |
Christian Minet, Sergi Duque Biarge, Julia Jaenicke, Ulrich Münzer, Christoph Mayer, Jonas Franke, Agust Gudmundsson, Alessandro Parizzi, Thomas Fritz, Michael Eineder |
Konferenz |
EGU General Assembly 2014
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 16 (2014) |
Datensatznummer |
250090691
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Publikation (Nr.) |
EGU/EGU2014-4945.pdf |
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Zusammenfassung |
Subglacial volcanic eruptions often provide indications of activity some time before the
actual catastrophic event. Surface undulations appear on top of the ice cap and meltwater
torrents can occur at the glacier margin. Even large scale uplifts of ice caps have been
observed. Within the project IsViews a processing chain, based on high spatially and
temporally resolved remote sensing imagery, will be developed in order to automatically
identify such early indications. The main data used for this analysis are acquired by the
TerraSAR-X, TanDEM-X and RapidEye satellites. First investigations concerning the
feasibility of the near real-time warning system and the general baseline conditions are
carried out on two large plateau glaciers in southern Iceland, namely Mýrdalsjökull and
Vatnajökull.
Within the 2013 IsViews field work an experiment was started in order to test a new way of
glacier monitoring. Two test sites were established on the Mýrdalsjökull ice cap (one at the
equilibrium line and one below), each consisting of a permanent GPS station and two nearby
RADAR reflectors. These RADAR reflectors are specially designed Top-Hat reflectors, which
are cheap to manufacture, small (50 cm diameter) and lightweight and therefore easy to
handle, transport and deploy. Their special design makes them visible in SAR images
independent of orientation, so different acquisition geometries and even different sensors can
be used. The drawback of the small, low reflecting Top-Hat can be overcome by
using the newly implemented Staring Spotlight Mode of the German SAR Satellite
TerraSAR-X, providing an unprecedented resolution of down to 20 cm in the azimuth
direction.
The reflectors, as point targets, allow absolute positioning within the cm-level in the
TerraSAR-X data. Time series of SAR data can be used to derive position and altitude
changes of the reflector itself and possibly even melting rates by exploiting the different
signal paths. The visibility of the Top-Hat reflectors has been confirmed in various test
acquisitions shortly after their deployment, and initial position measurements have been
carried out. Further acquisitions will be recorded once the reflectors emerge from the winter
snow cover, and correlation of the measurements will be performed once the data of the GPS
stations are received in March 2014.
The ease of deploying these new reflectors combined with the high-resolution capabilities of
the TerraSAR-X satellite provides new monitoring possibilities, not only for glacial flow
dynamics but also for rock movements and deformation of infrastructure. |
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