A novel algorithm is presented to solve the ambiguity problem of across-track velocity estimation for moving targets in airborne sidelooking SAR system.In this method

the across-track velocity can be unambiguously estimated according to the slope calculated by Radon transform of the profile extracted from the echo’s range walk trajectory.In order to solve the problem the along-track velocity estimation is influenced by the across-track acceleration

we propose a new along-track velocity estimation approach.The along-track velocity can be obtained by the real synthetic aperture time (synthetic aperture length) of target.Proposed methods can be applied to both single- and multi-channel SAR systems.The validity and practicability are verified by the simulated and real measured data.