曲线上中线点坐标的简便算法

A simple calculation method for coordinates of center line points on a curve

用极坐标法测设曲线的首要条件是：已知测站点和待定点的统一坐标．本文从待定点与JD（交点）及相关切线之间的几何关系出发，先求出它与JD的距离及坐标方位角，然后通过坐标正算，再求出它在统一坐标系中的坐标．

To locate a curvy route with polar coordinate method, one must know the coordinates of the station point and the point being located (PBL). In this thesis, from the geometric relations between PBL, the junction point (JP) and the corresponding tangent, thedistance between PBL and JP, and the azimuth of the direct line through PBL and JP are calculated firstly. Then, through direct coordinate calculations, the coordinates of PBL in thecommon coordinate system are determined.