Weighted two-dimensional phase unwrapping

In order to compute surface elevation accurately from a complex SAR image the phase must be unwrapped successfully. If the complex image is noisy or if it contains bright reflectors, unwrapping the phase by conventional methods will result in surface elevation maps with significantly degraded accuracy. The paper presents a new algorithm that successfully unwraps the phase in a noisy complex image, and that also limits the distortion in the unwrapped phase caused by bright reflectors. The algorithm automatically identifies regions of noisy data in the complex image, and then derives a weighting factor that essentially assigns noisy phase angles a weight of zero while leaving unchanged the phase angles in regions of high signal-to-noise ratio. The new algorithm also derives a second weighting factor that limits the effects of bright reflectors on the unwrapped phase. Results of simulations are presented that show the advantages the new algorithm over conventional methods of phase unwrapping