What does altimeter setting indicate?

The altimeter setting indicates the pressure value that an aircraft should use to determine its altitude above sea level. This is crucial for aviation, as pilots rely on accurate altitude readings to maintain safe vertical separation from terrain and other aircraft.

When the altimeter is set to the local altimeter setting, it allows the aircraft's altimeter to provide a correct reading of the aircraft’s height relative to sea level. Pilots must adjust their altimeters based on local air pressure to ensure their altitude indications reflect the true height above mean sea level.

This is particularly important in varying weather conditions, where atmospheric pressure changes can significantly impact altitude readings. Accurate altitude information is essential for safe flight operations, especially during takeoff, landing, and when flying in close proximity to other aircraft and terrain.