IMAGE ANALYSIS: PROBLEMS, PROGRESS AND PROSPECTS**The support of the Defense Advanced Research Projects Agency and the U.S. Army Night Vision Laboratory under Contract DAAG-53-76C-0138 (DARPA Order 3206) is gratefully acknowledged, as is the help of Janet Salzman in preparing this paper. A different version of this paper was presented at the Sixth International Conference on Pattern Recognition in Munich, FRG, in October 1982.