Least-squares curve fitting for velocity and time zero

Indirect least-squares algorithms developed for bistatic antenna configurations are derived to simultaneously invert for propagation velocity, time zero, depth, and lateral offset for buried objects approximating point diffractors. An alternative direct algorithm is derived for antenna geometries approximating the monostatic antenna configuration. Least-squares fitting for velocity, depth, and lateral offset using multiple diffraction curves is combined with a time zero grid search algorithm to provide a robust solution when inverting for time zero.