straight baseline

例句：

1. 1.The engineer used a straight baseline to measure the distance between two points on the map.
   工程师使用一条直线基准线来测量地图上两点之间的距离。
2. 2. The construction crew followed the straight baseline to ensure that the new road was level and straight.
   施工队沿着直线基准线行走，以确保新路是平直的。
3. 3. The scientist used a straight baseline to draw an accurate diagram of the object's shape.
   科学家使用一条直线基准线来绘制物体形状的准确图。