This award will enable Prof. George Nagy of Rensselaer Polytechnic Institute and Dr. Bianca Falcidieno of the Italian National Research Council in Genova, Italy, to continue a successful collaboration that started in 1981. An algorithm developed in the previous stage of the research is used to define a data structure, called a visibility map, on an appropriately triangulated terrain model. The map shows whether there is an unimpeded line of sight between any two points. The algorithm is related to existing hidden-surface algorithms, but incorporates concepts based on the unique characteristics of the problem. Additionally, the global nature of the visibility model provides a useful alternative to partial derivatives for defining topographic entities. Other algorithms have been developed applying the resulting visibility map to rank order the best observation points. Among the problems to be considered by the investigators are: line of sight (television, FM, radar) communications and surveillance problems; hidden paths; orientation and navigation; the inverse transform from the visibility map to the original terrain data; data compression; and the extraction of significant terrain features such as ridges and valleys. The U.S. PI will bring to the collaboration experience with computer vision, optical scanning, and engineering applications of pattern recognition, remote sensing, geographic data processing, and computational geometry. The Italian side will provide expertise in computational geography, computer cartography, computer graphics, solid modeling, and graph theory. The research is expected to contribute to computational geometry, to topographic information systems, and to telecommunications.
