Definition 1 of 2
Plain English Meaning
How far the controller in the tower can see, looking out from up in the tower cab. Because the tower is high up, this view can differ from what a person sees standing on the airport surface.
Full Definition
The prevailing visibility reported from the air traffic control tower cab, observed by the controller from tower height rather than from ground level. When an official weather observer is located in the tower, this value becomes the official visibility for the airport whenever it is lower than the surface visibility reported from the ground.
Context Anchor
Seen in airport weather reports and discussions when the view from the is reported separately from the main surface visibility.