DETECTION AND QUANTIFICATION OF ROCK GLACIER DEFORMATION USING ERS D-InSAR DATA

Synthetic Aperture Radar (SAR) systems normally record both the amplitude and the phase of the backscattered echoes. However, the phase of a single backscattered image is of no use and therefore, conventionally the amplitude or intensity image is usually provided to the user. But on the contrary, the phase difference of two backscattered SAR images of the same area on the ground taken at slightly different view angles can be utilised to generate digital elevation model (DEM) of the imaged terrain [5,8,12]. This technique is known as SAR interferometry (InSAR) and can be extended to differential SAR interferometry (D-InSAR) to detect surface changes in the order of few cm [2]. Although the D-InSAR has been shown to successfully derive surface displacement in the radar line-of-sight caused by earthquakes [7] or mass movements in alpine and arctic terrain [9,10], a number of questions related to the properties of rock glaciers and the imaging geometry of the SAR sensor remain to be answered. These include the relative small size of the rock glaciers in comparison to the SAR pixel resolution, the rough surface topography composed of debris and rocks, the perennial snow patches and snow cover most of the year in the areas of interest, the rather small flow velocities of active rock glaciers in the range of centimetres to few meters (in some cases) per year, the look angle of the SAR sensor, and the geometric and temporal baselines requirements for successful D-InSAR data sets.