What is the primary function of an altimeter in an aircraft?

The primary function of an altimeter in an aircraft is to indicate altitude. An altimeter is an essential instrument that helps pilots gauge their aircraft's height above a reference point, typically sea level. It works by measuring the atmospheric pressure; as an aircraft ascends, the air pressure decreases, and the altimeter translates this change in pressure into altitude readings. This information is crucial for maintaining safe distances above terrain and for compliance with air traffic control regulations. Pilots rely on accurate altitude readings to ensure safe navigation and to avoid obstacles, especially during takeoff and landing phases.