What is referred to as pressure altitude?

Pressure altitude refers to the altitude at which a particular atmospheric pressure is observed, and it is specifically based on the standard atmospheric pressure of 29.92 inches of mercury (Hg) at sea level. This standard is used in aviation to ensure that altimeters, which measure atmospheric pressure, provide a consistent reference for altitude across different aircraft and conditions.

When pilots refer to pressure altitude, they are essentially referencing a standardized measurement that does not account for variations due to temperature or local atmospheric pressure deviations. Therefore, pressure altitude is a critical concept for ensuring safe separation between aircraft, as it allows for a uniform understanding of altitude irrespective of current weather conditions.

The other options describe different forms or definitions of altitude. Altitude above sea level relates to the actual height without any pressure standardization, altitude corrected for temperature addresses variations based on temperature deviations from the standard atmosphere, and height above the transition level concerns altitude in relation to the airspace structure, particularly in the context of vertical navigation. None of these options directly capture the essence of pressure altitude as accurately as the reference to the standard 29.92 inches of mercury.