1. In the method of determining speed in a forward-looking, coherent pulse doppler synthetic aperture signal processing mapping radar apparatus, the steps of: (a) providing a forward-looking, coherent pulse doppler synthetic aperture signal processing mapping radar apparatus having range gating means for sorting return signals in accordance with range from which said signals are reflected, and in which the return signals are applied to respective range channels, each of said range channels including parabolic focusing in response to focus term signals applied thereto, doppler filtering and storage, each of said channels thereby capable of providing a plurality of successive signals representative of the magnitude of the return signal at each of a plurality of different successive doppler frequencies, the successive signals for all of said range channels comprising a range/doppler matrix of magnitude of reflectivity; (b) providing focus term signals relating to a nominal speed and an arbitrary selected one of said range channels and processing signals in said apparatus therewith; (c) determining the values of contrast of signals for each range channels of said range/doppler matrix; (d) determining a range for which contrast will be maximum; (e) calculating speed as the square root of the sum of: the square of the range rate with the product of range acceleration times the range selected in step (d).