底面
bottom; bottom side; bottom surface
地面层
ground floor; first floor
地面控制
ground control (of airborne or space operation)
地面核爆炸
surface nuclear explosion
地面零点
Ground Zero (refers to the site of the World Trade Center destroyed in 9-11-2001 attack)
占地面积
floor area; occupied area; footprint (of a building, piece of equipment etc)