plumb pointtriangulation

例句：

1. 1. The plumb line is used to measure the level of a building.
   铅垂线用于测量建筑物的水平面。
2. 2. The construction crew carefully measured the plumb line before starting work.
   施工队在开始工作前仔细测量了铅垂线。
3. 3. The engineer used the plumb line to ensure the foundation was level.
   工程师使用铅垂线确保地基水平。