InSAR (Interferometric SAR)

InSAR, interferometric synthetic aperture radar, measures surface deformation by differencing the phase of two SAR images of the same scene from slightly different times or positions. Each phase fringe corresponds to a line-of-sight change of half the radar wavelength, near 2.8 cm at C-band, so subsidence, uplift, and slow slip resolve to millimeters per year over a season of acquisitions. On coasts it tracks land subsidence that adds to relative sea level rise, port and structure settlement, and delta sinking. Sentinel-1 and the RADARSAT Constellation supply the data; SWOT extends the cross-track interferometry idea to water-surface height itself.