Detecting and Geo-Locating Moving Ground Targets in Airborne QuickSAR 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. The first stage of Keystone Formatting simultaneously and automatically compensates for range walk due to the radial velocity component of each moving target, independent of the number of targets or the value of each target's radial velocity with respect to the ground. As is well known, target radial motion also causes moving targets to appear in synthetic aperture radar images at locations offset from their true instantaneous locations on the ground. In an appropriately configured multichannel radar, the interferometric phase values associated with all non-moving points on the ground can be made to appear as a continuum of phase differences while the moving targets appear as interferometric phase discontinuities. By multiple threshold comparisons and grouping of pixels within the intensity and the phase images, we show that it is possible to reliably detect and accurately georegister moving targets within short duration SAR (QuickSAR) images.