Tracking Moving Ground Targets from Airborne SAR via Keystoning and Multiple Phase Center Interferometry

Without some form of motion compensation, SAR images experience significant range walk and can be quite blurred. In 1997, MITRE reported development of the Keystone Process. Keystone Formatting simultaneously compensates for multiple target motion at multiple radial velocities. The target motion causes the moving targets to appear at locations different from their true instantaneous locations on the ground. In a corresponding interferometric phase image, all points on the ground nominally appear as a continuum of phase differences while the moving targets appear as discontinuities. By threshold comparisons within the intensity and the phase images, we and others have shown that it is possible to detect and georegister moving targets in the SAR.