on a rail instead of a satellite moving around an orbit. SAR technique allows 2D radar image of the investigated scenario to be achieved, with a high range resolution (along the instrumental line of sight) and cross-range resolution (along the scan direction). Two antennas respectively emit and receive microwave signals and, by calculating the phase difference between two measurements taken in two different times, it is possible to compute the displacement of all the pixels of the SAR image. The accuracy in the displacement measurement is of the same order of magnitude as the EM wavelength and depends also on the specific local and atmospheric conditions. Applications Tectonic InSAR can be used to measure tectonic deformation, for example ground movements due to earthquakes. It was first used for the 1992 Landers earthquake, but has since been utilised extensively for a wide variety of earthquakes all over the world. In particular the 1999 Izmit and 2003 Bam earthquakes were extensively studied. InSAR can also be used to monitor creep and strain accumulation on faults. Volcanic InSAR can be used in a variety of volcanic settings, including deformation associated with eruptions, inter-eruption strain caused by changes in magma distribution at depth, gravitational spreading of volcanic edifices, and volcano-tectonic deformation signals. Early work on volcanic InSAR included studies on Mount Etna, and Kilauea, with many more volcanoes being studied as the field developed. The technique is now widely used for academic research into volcanic deformation, although its use as an operational monitoring technique for volcano observatories has been limited by issues such as orbital repeat times, lack of archived data, coherence and atmospheric errors. Recently InSAR has been used to study rifting processes in Ethiopia. Subsidence Ground subsidence from a variety of causes has been successfully measured using InSAR, in particular subsidence caused by oil or water extraction from underground reservoirs, subsurface mining and collapse of old mines. Thus, InSAR has become an indispensable tool to satisfactorily address many subsidence studies. Tomás et al. performed a cost analysis that allowed to identify the strongest points of InSAR techniques compared with other conventional techniques: (1) higher data acquisition frequency and spatial coverage; and (2) lower annual cost per measurement point and per square kilometre. Landslides Although InSAR technique can present some limitations when applied to landslides, it can also be used for monitoring landscape features such as landslides. Ice flow Glacial motion and deformation