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Summary of Proposal LAN1426

TitleDetection and monitoring of French south alps rockglaciers using TSX D-InSAR data.
Investigator Echelard, Thomas - Gipsa-Lab, Images et Signal
Team Member
Doctor Bodin, Xavier - EDYTEM, Environnements, Dynamiques et Territoires de la Montagne
Professor Schoeneich, Philippe - Institut de Géographie Alpine, PACTE
Doctor Gay, Michel - Gipsa-Lab, Images et Signal
Summary

The aim of the study proposed here is to better understand the evolution of superficial movements which are inherent to the permafrost presence in relation with current and past climate variability. Permafrost is defined as the portion of ground where temperatures are less than or equal to 0 ° C for at least two consecutive years. Its distribution is poorly known and can be assessed by observation of indirect effects, such as the surface movements of rock glaciers, or by modeling.

We have started by a study with ERS archive data and we have obtained good results (Echelard et al., 2012). However three main factors have limited our study and led us to propose this TSX project: i) the age of the data (20 years) which requires us to be cautious about the results obtained on ERS data and what is really happening today in the field ii) the length of spatial baselines which limit sharply the number of images usable for differential radar interferometry processing iii) and the resolution of ERS images (20m in ground geometry) which are inadequate for features that sometimes are only 100 to 200 m long. Nevertheless, this study allowed us to target the most relevant areas (Queyras - Ubaye) for a more thorough study. That’s why it seems relevant today to acquire new SAR images on the French Alps for four mains reasons:

  • update SAR data in the french Alps,
  • refine the D-InSAR analysis using TSX resolution (Stripmap mode interferometric data, single polarization, 3m resolution, 30 km swath width, acquisition time 22 day interval) and D-GPS measurements for several years carried on a dozen rock glaciers in the French Alps,
  • use the 5 continuous GPS data which will set up on rockglaciers in summer 2012 to compare SAR data and field data,
  • advance the analysis of SAR images applied on rockglaciers by exploring and comparing different methods such as offset tracking and classic D-InSAR.
In long term we wish to show that it is possible to monitor the evolution of rockglaciers using SAR images rather than GPS measurements that are selective and limited.

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