利用鼠标绘制折线段，然后输入垂距，在折线段的两边以不同的颜色分别画两条与原折线段条平行的新折线段，这是GIS中绘制缓冲区的基础-Using the mouse draw off line, then enter the vertical distance, on both sides of the fold line with two different colors were painted with the original fold line parallel to the new sec