What does an altimeter measure in the Cessna 172?

An altimeter measures the aircraft's altitude above sea level by detecting changes in atmospheric pressure. As an aircraft climbs or descends, the air pressure decreases or increases, respectively, which the altimeter uses to determine the altitude. In the Cessna 172, this instrument is crucial for pilots to maintain safe altitudes during flight and to ensure proper separation from terrain and other aircraft.

Understanding the altitude above sea level is essential for navigation and compliance with air traffic regulations, as it helps pilots make informed decisions on course and altitude. Just as a reminder, while other options relate to different flight parameters or conditions, only the measurement of altitude in relation to sea level correctly aligns with the function of the altimeter in the Cessna 172.