Detecting slope deformation using two-pass differential interferometry : implications for landslide studies on Earth and other planetary bodies.

Landslide features have been identified on Earth and the Moon, Mars, Venus, as well on the Jovian moons. By focusing on a terrestrial landslide complex we test the operational parameters of RADARSAT-1 and the use of two-pass differential interferometry to detect change, to map its extent, and to measure the amount of movement over a given time period. RADARSAT-1 was chosen because of its variable imaging modes and geometry. For investigations of landslide motions using remote sensing techniques, repeat-pass data are required. Synthetic aperture radar (SAR) interferometry (InSAR) can ideally monitor movements across the whole surface of a landslide to a millimeteric precision, yielding a coverage significantly better than that obtained by ground instrumentation. Obtaining optimal data for InSAR analysis requires controlled orbital characteristics and imaging geometries, an understanding of the landslide characteristics and behavior, a cooperative surface, and mitigation of the factors that can affect phase. Using two-pass differential interferometry, a slope deformation map has been generated from RADARSAT-1 data for part of the Black Ven landslide (2°52′W, 50°40′N), on the south coast of England. Four months separate the InSAR pair during which time 0.03 m of subsidence was measured. From this a movement rate of 0.09 m/yr can be calculated. This agrees well with ground observations and an in situ record of movement, thus demonstrating that the technique can be used to investigate landslides. With further refinement it can provide more direct measurements of landslide deformation on Earth and other planetary bodies than are currently available