The barometric altitude is measured using which instrument?

The barometric altitude is specifically measured using the altimeter. This instrument works by detecting changes in air pressure as an aircraft ascends or descends. As altitude increases, air pressure decreases, and the altimeter uses this relationship to calculate the aircraft's elevation above sea level. It is a crucial instrument for pilots to understand their altitude during flight, especially in relation to terrain and air traffic.

The other options represent different types of instruments that serve different purposes: an accelerometer measures the acceleration of the aircraft, a true airspeed indicator calculates the aircraft's actual speed through the air, and an airspeed indicator measures the speed of the aircraft relative to the surrounding air. None of these instruments track altitude based on barometric pressure.