 Interferometric synthetic aperture radar ( <unk> ) is a radar technique used in geodesy and remote sensing . Satellite synthetic aperture radar images of a geographic feature are taken on separate days , and changes that have taken place between radar images taken on the separate days are recorded as fringes similar to those obtained in holographic interferometry . The technique can monitor <unk> to millimeter @-@ scale deformation resulting from earthquakes , volcanoes and landslides , and also has uses in structural engineering , in particular for the monitoring of subsidence and structural stability . Fig 20 shows Kilauea , an active volcano in Hawaii . Data acquired using the space shuttle Endeavour 's X @-@ band Synthetic Aperture Radar on April 13 , 1994 and October 4 , 1994 were used to generate interferometric fringes , which were overlaid on the X @-@ SAR image of Kilauea . 
