Pre-formation SAR to SAR image registration

A critical step in the formation of multi-pass IFSAR and CCD products involves the registration to subpixel scales of two complex SAR images. This is usually performed as a two step process where correspondences between the images are determined followed by a warping of the imagery. Since more information is available in the phase history data (PHD) it might be expected that improved registration results could be achieved. This paper investigates a number of registration approaches in the PHD and shows that the techniques are equivalent to each other and to registration in the image domain. It is also demonstrated that processing in the PHD, although potentially minimizing the impact of numerical errors from resampling introduces complexity when estimating local registration estimates and has difficulty in regions that decorrelate.