1. A computer-implemented method of estimating 3D target information, said computer executing the steps of: collecting coherent radar data while flying an aerial platform in a nonlinear flight path with nonzero acceleration out of the slant plane while imaging a ground-based target; forming a two-dimensional synthetic aperture radar (SAR) image from the coherent radar data using a phase-preserving technique; identifying and masking the ground-based target in the 2D SAR image to identify target pixels; establishing a zero height reference plane that supports the target; deriving a vector of complex-valued time samples associated with one of the target pixels; running a Barankin Estimator on the vector of complex-valued time samples to provide a Barankin estimate {circumflex over (α)} B of a quadratic phase parameter α for the target pixel; and scaling the Barankin estimate {circumflex over (α)} B to a pixel height z relative to the zero height reference plane for the target pixel.