ABSTRACT
In many instances, humans accomplish recognition by a Gestalt comparison of the feature with a catalog, either in hand or in memory. Some recognition tasks require an extensive catalog and organization, as represented by the typical field guides for identifying birds, plants, and so on. The horizontal axis of each plot is the magnitude of the differences in the parameters for each airplane shape. One thing that cross-correlation is quite good at is finding a feature in a cluttered or camouflaged scene. In some situations, such as searching reconnaissance images for objects of military interest, the cross-correlation is performed with target images oriented at angles in steps of about 15 to 20 degrees. When shape is used for classification, choosing the appropriate shape parameters may be done by humans based on prior knowledge and experience, or mathematically by techniques such as principal components analysis, stepwise regression, or discriminant analysis.
