Abstract:
Geographic information systems generally have an ability to enlarge or reduce map display area thus they can easily change the map scale. However, in the most cases, the maps displayed are not properly represented according to the cartography principle. Generalization is a process to manage all the information on the map ocnsidering the reducing scale from the larger scale map to properly represent information on the middle scale and small scale map. This is achieved by reducing information of objects on the map which is too excessive to present and therefore reduce legibility of the map. This research applied the generalization onto a geographic information system using the theory of Nickerson & Freeman. They proposed 3 processes of generalization which are selection, simplification and displacement. The generalization will reduce details a map to a legible level on the basis of its objective. In this research, a map at scale 1:6,000 was automatically generalized to scale 1:10,000, 1:20,000, 1:50,000 and 1:250,000. The rules used are established from the existing topographic map analysis. The methodology used in the programs are evaluated by a comparison between the resulting maps generalized at various scales, 1:10,000 1:20,000 1:50,000 and 1:250,000, and their corresponding existing map compiled by Royal Thai Survey Development (RTSD) and Japan International Corporation Agency (JICA). In most cases the comparison is well matched so that the methodology is considered acceptable. Thus, this thesis finally provides a workable process that can act as a fundamental methodology for the generalization in the future