Which sensor's readings are used to determine altitude and airspeed by measuring atmospheric pressure?

• A. Barometer
• B. IMU
• C. GPS
• D. Magnetometer

Answer: (A)

The ability to estimate altitude and airspeed from atmospheric pressure comes from a barometer. Ambient atmospheric pressure decreases with altitude, so a barometer’s pressure reading is used to compute how high you are above sea level. For airspeed, you combine the static pressure from the barometer with the total pressure measured by a pitot tube to obtain dynamic pressure, which is then converted into speed. The other sensors don’t measure atmospheric pressure directly: an IMU tracks acceleration and orientation, GPS gives position and velocity (not pressure-based), and a magnetometer reads magnetic field direction.