What is the primary function of an altimeter?

The primary function of an altimeter is to measure altitude above a reference point, typically sea level. This device is crucial for pilots as it allows them to maintain an appropriate altitude during flight, which is essential for safety and compliance with air traffic regulations. An altimeter uses atmospheric pressure changes to determine its altitude; as altitude increases, atmospheric pressure decreases. By calibrating the instrument based on a known pressure at sea level, the altimeter can accurately indicate the aircraft's altitude above that reference point.

This measurement is vital for flying in controlled airspace, navigating safely during ascent and descent, avoiding obstacles, and ensuring safe separation from other aircraft. The ability to measure altitude in relation to a reference point directly impacts flight safety and operational efficiency.