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InSAR: How does it work?

How InSAR observes the Earth

 

InSAR relies on spaceborne radar sensors to acquire images of the Earth’s surface at different acquisition times. Satellite platforms transmit microwave pulses toward the ground and record the backscattered signals returned to the sensor.  

Because microwave signals are independent of solar illumination and largely unaffected by atmospheric conditions, SAR systems ensure consistent, all-weather, day-and-night data acquisition. This enables systematic and reliable monitoring of natural and built environments.  

Converting radar signals into deformation measurements: InSAR exploits the complex nature of SAR imagery. Each pixel contains both:  

•  Amplitude, representing the intensity of the backscattered signal  
•  Phase, representing the distance traveled by the radar wave between the satellite and the target  

 

From radar signals to ground deformation

 

InSAR technique analyzes the phase component of two or more SAR images acquired over the same area at different times. By computing the phase difference, it is possible to measure variations in the radar signal travel path with sub-wavelength sensitivity.  

After accounting for topographic, atmospheric, and orbital contributions, the remaining phase component is directly related to surface displacement along the satellite’s line-of-sight (LOS). This enables the quantification of ground motion with millimetric precision over large spatial extents.  

In summary, InSAR transforms repeated radar acquisitions into precise, spatially continuous deformation measurements, providing a robust and scalable solution for ground motion monitoring.