Definition
An altitude derived from atmospheric pressure, measured by a barometric altimeter and referenced to a selected pressure setting (such as the local altimeter setting or the standard 29.92 inHg). It represents the aircraft's height above that pressure reference, not its true height above the ground or above sea level under all conditions.
Plain English
The altitude your altimeter shows based on air pressure. As you climb, air pressure drops, and the altimeter converts that pressure change into a height reading.
Context Anchor
Seen in instrument flying, altimeter use, air data displays, and Ground Proximity Warning System discussions where pressure-based altitude is one of the system inputs.
Derivation
From 'barometer' (Greek baros, weight, plus metron, measure) -- literally 'a measurer of weight,' meaning the weight of the atmosphere pressing down. Barometric altitude is altitude figured out by measuring that pressure.
Why Pilots Care
Provides the primary vertical reference for terrain clearance, traffic separation, and approach altitudes when flying on instruments.
Grounding Statement
As an aircraft climbs, the air pressure around it normally gets lower, and the altimeter converts that pressure change into an altitude reading.
Intuition Check
Barometric altitude does not mean actual height above the ground. It means altitude calculated from air pressure, based on the pressure setting being used.
Example Sentence 1
The GPWS compares the aircraft's barometric altitude to a database of terrain elevations to determine whether a warning is required.
Example Sentence 2
GPWS compared the aircraft's barometric altitude trend with terrain data to issue a timely warning.