groundline

例句：

1. 1. The groundline of the construction project is set at 10 meters above sea level.
   该项目的施工底线定在海拔10米以上。
2. 2.The team needs to maintain a safe distance from the groundline during the game.
   队伍在比赛中需要保持在安全距离内，不越过底线。
3. 3. The new regulations will ensure that all companies comply with the groundline in terms of environmental protection.
   新规定将确保所有公司在环保方面都遵守底线。