Which of the following best defines the altimeter?

The altimeter is specifically designed to measure altitude, which is the height of an object above a reference point, typically above sea level. In aviation, it is crucial for pilots to have accurate altitude information to maintain safe airspace separation and ensure proper navigation. The altimeter works by measuring the atmospheric pressure, which decreases as altitude increases; this allows it to provide a precise reading of an aircraft's current height.

Understanding how the altimeter operates is vital for flight safety, especially during takeoff, ascent, cruising, descent, and landing phases. The ability to determine altitude accurately can help prevent mid-air collisions and ensure compliance with air traffic control instructions. This function is critical for both VFR (Visual Flight Rules) and IFR (Instrument Flight Rules) operations, making the correct identification of the altimeter as a device for measuring altitude essential for aviation.