DESIGN AND IMPLEMENTATION OF HIGH PRECISION MAP SYMBOL LIBRARY BASED ON GDI

The rapid development of computer and the emergence of digital map and electronic map is motivating Geographic Information System greatly. At the same time, with the progress of data capturing technologies, voluminous geographical data has been accumulated in databases and still increasing rapidly. We are on the verge a necessary-solved problem how to visualize the map data to the users in a direct, clear and visual way. In order to meet these requirements, map symbol library has appeared. As the symbolization of the vector map, the map features are transformed to the visual symbols that the users can read and extract more information. Therefore, symbolizing map features can communicate information more clearly and efficiently. In this paper, the authors introduce open map symbol design, the oriented-object system design and implementation. The software is developed by Visual C++ 6.0 and has friendly interface, convenient operation and great function; and it uses the parametric data structure and high precision geometry data to organize the symbols and uses GDI+ to draw the symbols. The users can design the relevant symbols easily by using the program. And it meets with the needs of the national topographic map specification. Firstly, the research and development situation of the map symbol library are summarized, the significances of design and implementation of map symbol library are discussed, then the total structure of the symbol library system and the different graphic elements are proposed with emphasis. Secondly, some functions and characteristic of the symbol library system are described, such as: Special data structure of the line symbol is to improve the drawing speed and have a good drawing effect. The feasibility of the symbol library system by applying the symbol library to symbolize the map is proved. Finally the author gives some conclusion and comments on the prospects of the application and development of the symbol library.