垂线

The plumbline is always perpendicular to the horizontal plane.

铅线总于水平面的。

A new means of determining astro geodetic deflection of the vertical CCD automatic astrometer and the new method to determine the difference of height anomalies between two points are described.

介绍当今确定天文大地线偏差的新仪器———CCD自动天体测量仪和确定点间高程异常差的新方法。