Landslide Observation from ALOS-2/PALSAR-2 Data (Image Correlation Techniques and Sar Interferometry). Application to Salazie Circle Landslides (La Reunion Island)

Abstract : In the presented study our purpose is to show the interest of space-borne high-resolution L-band Synthetic Aperture Radar (SAR) images (ALOS-2/PALSAR2 data in SM1 mode) for mapping deformation of slow landslides. The methods we combined are sub-pixel correlation offset tracking techniques and differential SAR interferometry. Hell-bourg and Grand Ilet landslides (our test cases) are located on La Réunion Island in the Indian Ocean with motions up to about 1 m/y. The produced deformation maps resulted better than those obtained in previous studies with C or X band SAR data or with current Sentinel-1 data as L-band data are less affected by the vegetated cover than X-or C-band data. Finally, the possibility of deriving 3D mapping of the displacement by combining ascending and descending acquisitions (each one provides 2 components of the deformation: line of sight and azimuth) is investigated.