Altimeter

Altimeter is a cockpit instrument that indicates the aircraft altitude by measuring atmospheric pressure. As altitude increases, atmospheric pressure decreases, and the altimeter translates this pressure change into an altitude reading.

Types:

• Barometric altimeter: Uses static pressure — the standard instrument, accuracy depends on correct pressure setting (QNH)
• Radar altimeter (radio altimeter): Measures actual height AGL by timing radio signals bounced off the ground — used for precision approaches and GPWS
• GPS altitude: Derived from satellite signals — geometric height above ellipsoid