Sub-pixelic Image Registration for SAR Interferometry Coherence Optimization

This paper presents a methodology for the registration of an Interferometric Synthetic Aperture radar (InSAR) pair images with a sub-pixelic precision performed in the Fourier domain, using the Fast Fourier Transform (FFT). We look for the maximum of the modulus of the cross-correlation coefficient of both images on a window dimensions of 2x2 pixels using an iterative process. This will be possible in the Fourier domain, since a shift in the spatial domain is achieved by a multiplication with an exponential factor (which is the real shift less than one pixel) in the frequency domain. It is shown that the proposed sub-pixelic approach allows the coregistration of the images with an accuracy up to a tenth of a pixel (and even less).