A method for signal conditioning of signals from a two-dimensional image by calculating the motion of an image in relation to an image plane. Two-dimensional structures in the image are correlated between images separated in time, using Radon transforms for two or more angles in order to reduce the correlation calculations from two-dimensional correlation to correlation of two or more one-dimensional projections. The one-dimensional projections are differentiated to obtain the gradients of the projections as the basis for the correlation of images separated in time and signal conditioning. The magnitude of the gradients of the projections is ignored and the sign value of the gradients is used for a binary representation as the basis for the correlation of images separated in time.