What does "ground visibility" refer to in aviation?

Ground visibility refers to the visibility conditions present at an aerodrome, which can be reported either by a trained observer or through an automated system. This measurement is important in aviation as it helps pilots and air traffic control assess the safety of operations during takeoff, landing, and taxiing. Ground visibility provides critical information about how far one can see horizontally over the ground, which is essential for maintaining visual separation between aircraft and obstacles at an airport.

The other options do touch on aspects related to visibility but do not perfectly define ground visibility. The visibility reported from the control tower may include various types of visibility data but does not specifically isolate what ground visibility means. Visibility from the cockpit of an aircraft focuses on the pilot's perspective, which can be influenced by many factors such as weather and aircraft design, rather than being a standardized measurement at the aerodrome. Likewise, limiting visibility considerations solely to the runway does not encompass the broader context of ground visibility that includes the entire area surrounding an aerodrome.