用VB实现交互式CAD系统，能够绘制简单图形，如直线段，矩形，圆形等；绘制独立符号，如GPS点，水准点等；绘制线状符号，如陡坎，城墙等。-With VB interactive CAD system, able to draw simple graphics, such as line segments, rectangles, circles, etc.　draw independent symbols, such as GPS points, level points　drawn line symbols, such as scarps, walls, etc.