Definition
The current barometric pressure value, expressed in inches of mercury (or hectopascals/millibars), provided by a nearby weather reporting station and entered into an aircraft's altimeter so the instrument reads true elevation above mean sea level at airports within that station's area. It corrects the altimeter for the actual air pressure at the surface in that location at that time.
Plain English
The pressure number a pilot dials into the altimeter, taken from a weather station near where they are flying, so the altimeter shows the correct height above sea level for that area.
Context Anchor
Seen when setting the sensitive altimeter before takeoff, during arrival, or after receiving updated weather or air traffic control information.
Derivation
"Local" simply means "of that place" — the setting comes from a station near the aircraft, not a distant or standard value. Naming it "local" emphasizes that the correction is only valid in the area around the reporting station.
Why Pilots Care
Correct use prevents altitude errors that could lead to controlled flight into terrain or airspace violations.
Grounding Statement
Air pressure changes from place to place and over time, so the altimeter needs the current nearby pressure setting to stay aligned with the local area.
Intuition Check
“Local” does not mean the altimeter is measuring the ground directly below the airplane. It means the pressure setting comes from a nearby reporting location and is used for that area.
Example Sentence 1
Approaching the field, the pilot listened to the ATIS and set the local altimeter setting of 30.12 in the Kollsman window.
Example Sentence 2
ATC issued the local altimeter setting for the arrival airport so the pilot could maintain proper altitude on approach.