Synthetic Aperture Radar (SAR) is a side-looking, active (produces its own illumination), radar imaging system that transmits a pulsed microwave signal towards the earth and records both the amplitude and phase of the back-scattered signal that returns to the antenna. Interferometric SAR (InSAR) is a technique that compares the amplitude and phase signals received during one pass of the SAR platform over a specific geographic area with the amplitude and phase signals received during a second pass of the platform over the same area but at a different time. InSAR techniques, using satellite-based SAR platform data, can be used to produce land surface deformation products with sub cm-scale vertical resolution.

ADWR has been using InSAR since 2002 to determine the spatial extent, deformation rates, and time-series history of more than thirty land subsidence features within the Phoenix, Pinal and Tucson Active Management Areas (AMAs), and several groundwater basins outside Active Management Areas in Maricopa, La Paz, Cochise, Graham, Yuma, and Navajo Counties; all covering an area greater than 4,300 square miles.

ADWR has utilized InSAR data from the following satellites:

• ERS-1
• ERS-2
• Radarsat-1
• Envisat
• ALOS-1
• ALOS-2
• TerraSAR-X
• Radarsat-2
• Sentinel-1
• NISAR