ANALYSES OF VISIBILITY SITES ON TOPOGRAPHIC SURFACES

This paper introduces the analyses of visibility sites on topographic surfaces as a new area of application in geographical information systems. The analysis of visibility sites are important in several related research fields such as problems of surface representation in geographical information systems, visibility problems in computer graphics and the location allocation and the set covering problems in operations research. The application areas include pilot training simulation, navigation, scenic landscape assessment, terrain exploration, military surveillance, forest fire monitoring, locations of radio transmission stations and many others. Five types of site analysis using visibility information are discussed in this paper, including both fixed and variable heights of problems in visibility sites. Triangulated irregular networks are used to approximate an actual topographic surface. Algorithms are developed for extracting visibility information. Finally, three heuristic algorithms and their combinations are used to demonstrate the solutions for five problems of visibility sites.