| Map scanning digitizing is a primary method for obtaining geographical information, which was widely used for foundation of national 1:50000 geographical information database, and now is still in common use for obtaining overseas geographical information. So it is necessary for thorough and continual study. It makes sense to perfect theories and means of map scanning digitizing which could accelerate the producing of geographical information and hasten the developing of geographical information system.With practicality as the goal, this paper analyzes characters of map image, brings forward eigenvector-fitting algorithm, orientation-based search and consistency principle, develops a vectorizing system. Main content of the dissertation include:1. The paper synthetically expatiates the necessity of map scanning digitizing research, discusses the usual methods and procedure and analyzes existent problems.2. The paper analyzes color, shape, structure characters of map image, discusses the affection of scanning procedure and explains difficulties existed in digitizing.3. The paper studies the basic theories and general procedure, analyzes the difficulties, and brings forward a new procedure.4. The paper studies methods of map orientation, burrs removing, isolated point removing, hole filling up, background smoothing and tests them by experiments.5. The paper especially studies tracking methods of contour lines, road net, water system, analyzes difficulties existed in line tracking, brings forward a new method based on multicolor map.6. Using evaluating standards of road for reference, this paper brings forward a method for evaluating digitizing results.7. According to above methods, this paper develops a vectorizing system based on MicroStation, validates the feasibility and validity of the methods mentioned above, and has a helpful try for a better practical system. The results indicate that the method is fast computing and has a good stability to various complex cases. |
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