What is the purpose of the altimeter?

The purpose of the altimeter is to measure altitude above sea level. This instrument is essential for pilots as it provides vital information about the aircraft's height in relation to the surrounding terrain and the standard sea level pressure. The altimeter operates by measuring changes in atmospheric pressure; as the aircraft ascends, the air pressure decreases, and the altimeter reflects this change to display the current altitude.

An accurate understanding of altitude is crucial for various flight operations, such as ensuring safe clearance from terrain and obstacles, maintaining altitude during cruise flight, and performing appropriate approaches to landing. Thus, it's a fundamental instrument for navigation and safety in aviation.