1. A method for comparing appearances of an object comprising: (a) creating a set of templates of objects; (b) observing one of said objects subject to an unknown elastic transformation and creating a set of functions to describe the whole of the observed object; (c) applying a set of nonlinear functions to the set of functions of the observed object and the set of functions of at least one template to establish a linear relationship between the two; and (d) solving the linear relationship of (c) to determine the transformation parameters that when applied to the template will produce the observed object.