Design And Implementation Of Universal Digital Map Vector Symbol Editor

Map is an important component of Geographical Information System. As the language of map, map symbols can help user to acquire a mass of geography information, it is necessary to draw high quality map symbols in order to improve the legibility of map. Presently, there are large numbers of softwares which are able to draw digital map, but owing to the lacking of a uniform symbol system and drawing criterion, great differences lie among the maps drawn by those softwares, thus the reusability is low. In addition, lots of representative drawing softwares abroad cannot achieve our national requirement on map symbols.The target of this dissertation is to design and develop a general digital map vector symbol editor which can fulfil the national requirement by analyzing the map symbols in China and studying the drawing arithmetic and storage methods of map symbols.First of all, the graphical element method was employed to produce map symbols after analyzing the current map symbol classification and drawing method. Using this method, the data structure of symbols is more reasonable and consequently save more storage space.Then, the composition principle, symbolic algorithm and storage structure of different kinds of map symbols were studied carefully. On the base of that, the basic graphical element classification of point symbols was determined and the fairly good drawing method and symbolic algorithm were chosen to make the line symbols and fill symbols having higher quality and drawing speed. Besides, the symbolic algorithms of other two irregular symbols: semiline and semifill symbol and asymptote were studied so that the system could provide a complete symbol drawing function, which enhance the system's universality.Furthermore, a demand analysis was performed and the general digital map vector symbol editor was modeled based on the UML technology. With the aim of increasing the universality of the system, the configuration model, index mechanism and code standard of this system were determined by the demand analysis.Finally, the general digital map vector symbol editor was completed by VC++6.0. Using this system, the symbols that meet the national map graphic form standard can be attained. And during the development of this system, the GDI+and Design Pattern technologies were brought in. The former can improve drawing precision and drawing speed of map symbols, while the latter can enhance maintainability and expansibility of this system.