Multi-date ERS tandem interferogram analysis: application to alpine glaciers

Temperate glaciers are an indicator of the local effects of global climate change. For economical and security reasons in the surrounding areas, the monitoring of those geophysical objects is being a necessity. SAR data are expected to provide dense measurements of physical parameters which are necessary to detect significant changes and to constrain glacier flow models. In this paper, five descending one-day ERS1/2 tandem interferometric data pairs from July 1995 to April 1996 are studied in the Chamonix Mont-Blanc area (French Alps). This multi-temporal interferogram series is used to analyse the coherence levels and fringe patterns over nine glaciers. Moreover, when the coherence is sufficient, Differential SAR Interferometry (D-InSAR) processing are applicable to derive a three-dimensional (3-D) velocity fields. An expert knowledge and a ten years measurements analysis of glacier flow are used to fix the line of sight (LOS) displacement offset. Finally, an analysis of the wrapped phase difference between interferograms is exposed to detect the presence of residual topographic fringes and to characterize the surface flow field evolution.