Designing and Implementation of Map Symbol Database Based on COM

The map symbol database is a necessary part of geographical information system for displaying spatial data.This paper proposes a scheme of constructing aymbol base.The following is the content and innovation:The idea of partitioning the symbol base into three parts:the data file,the middle code and the application code;The idea of dividing the symbol base code into two levels:the abstract level and the application level;The idea of using many methods to solve one problem;The method of"cycle draw in x direction and pile in z direction" for solving the problem of line symbol's drawing;The algebra of morass symbol' random drawing and the algebra of flexile point symbol's drawing.