(2)
GROUND VISIBILITY - Prevailing horizontal visibility near the earth's surface as reported by the United States National Weather Service or an accredited observer.

(3)
PREVAILING VISIBILITY - The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle which need not necessarily be continuous.

(4)
RUNWAY VISIBILITY VALUE/RVV - The visibility determined for a particular runway by a transmissometer. A meter provides a continuous indication of the visibility (reported in statue miles or fractions of statue mile) for the runway. RVV is used in lieu of prevailing visibility in determining minimums for a particular runway.

(5)
RUNWAY VISUAL RANGE/RVR - An instrumentally derived value, based on standard calibrations, that represents the horizontal distance a pilot will see down the runway from the approach end; it is based on the sighting of either high intensity runway lights or on the visual contrast of other targets whichever yields the greater visual range. RVR, in contrast to prevailing or runway visibility, is based on what a pilot in a moving aircraft should see looking down the runway. RVR is horizontal visual range, not slant visual range. It is based on the measurement of a transmissometer made near the touchdown point of the instrument runway and is reported in hundreds of feet. RVR is used in lieu of Runway Visibility Value and/or prevailing visibility in determining minimums for a particular runway.

(a)
TOUCHDOWN RVR - The RVR visibility readout values obtained from RVR equipment serving the runway Touchdown Zone.