The image focus quality of multiple-pass 3D SAR imagery strongly depends on the accuracy of the between-pass
coherent image alignment. We present a method for forming a 3D SAR image from multiple coherently
aligned 2D SAR images collected at different viewing geometries, where the joint coherent alignment is performed
by directly optimizing the 3D SAR image entropy. Image entropy based focusing is inherently data-adaptive
and imposes only minimal assumptions about the SAR imagery such as it having a non-Gaussian distribution,
as opposed to interferometric based methods which typically rely on the assumption of one or a few bright
scatterers per resolution cell. We will show examples of coherently aligning and focusing 3D SAR imagery using
both simulated as well as measured multiple-pass SAR imagery.