This paper deals with the automatic evaluation of segmentation algorithms; the application framework is automatic target recognition within the specific case of infrared images of military vehicles. The approach consists in approximating the edges with generic B-spline functions; since the problem stated like this is too general, we use a spline template which has to be matched with the approximation by using some distance minimization. The difficult points of the problem are the indexing of the edges (with respect to the spline parameter sequence), the design of the spline itself has it must fit some specific requirements and the choice of a distance which is robust against noise and minor shape modifications. We show that some noticeable improvements happen by indexing edges points according to their projection onto a model from available a priori information. We finally explain how this spline model will be used to assess the edge detection step in an automatic vehicle recognition task.