trough compass

例句：

1. 1. The farmer used atrough compass to find his waythrough the field.
   农民使用沟渠指南针在田野中寻找方向。
2. 2. The oldman kept a trough compass inhis house for navigational purposes.
   老人在他的房子里保存了一个沟渠指南针，用于导航目的。
3. 3. The children used the trough compass to navigate their way homefrom the park.
   孩子们用沟渠指南针从公园导航回家。