Which instrument indicates height above mean sea level?

• A. Radar altimeter
• B. Barometric altimeter
• C. Attitude indicator
• D. Vertical speed indicator

Answer: (B)

Height above mean sea level is indicated by a barometric altimeter. It works by measuring the ambient air pressure, which falls as you climb, and converts that pressure into an altitude using the standard atmosphere model. To read height above mean sea level accurately, the altimeter must be set with the local altimeter setting (QNH), which calibrates the scale to sea level. If you use a field setting (QFE), it would display height above the airfield, not above sea level.

A radar altimeter measures distance to the terrain directly below, so it shows height above the ground, not above mean sea level. The attitude indicator simply shows the aircraft’s orientation relative to the horizon, and the vertical speed indicator shows how fast the aircraft is climbing or descending, not the current altitude.