In frequency computation of hydrology, empirical frequency has a significant effect on the results of the curvefitting method. 水文频率计算中，经验频率对适线法的结果有重大影响。
A new method was put forward to find the intersection line and determine its visibility of general position lines and planes using overlapped projection lines. 摘要提出用重影线法判断两重影直线的相对位置和求解一般位置直线与平面相交求交点判别可见性的新方法。
