Three dimensional (3D) autofocus remains a significant challenge for the development of practical 3D multipass
radar imaging. The current 2D radar autofocus methods are not readily extendable across sensor passes. We
propose a general framework that allows a class of data adaptive solutions for 3D auto-focus across passes with
minimal constraints on the scene contents. The key enabling assumption is that portions of the scene are sparse
in elevation which reduces the number of free variables and results in a system that is simultaneously solved
for scatterer heights and autofocus parameters. The proposed method extends 2-pass interferometric synthetic
aperture radar (IFSAR) methods to an arbitrary number of passes allowing the consideration of scattering from
multiple height locations. A specific case from the proposed autofocus framework is solved and demonstrates
autofocus and coherent multipass 3D estimation across the 8 passes of the "Gotcha Volumetric SAR Data Set"
X-Band radar data.