Review of Altitude Definitions

REVIEW OF ALTITUDE DEFINITIONS

Indicated altitude:

(IA) is the altitude reading on the aircraft altimeter when it is set to the

local area (nearest station) barometric pressure (altimeter setting).

Calibrated altitude: (CA) is indicated altitude corrected for instrument and installation

errors.

Pressure altitude:

(PA) is the calibrated altitude corrected for the difference between

local atmospheric pressure and the standard datum plane, 29.92.

Pressure altitude is the reference used to calculate True Airspeed.

True Altitude:

(TA) is the actual height of the aircraft above Mean Sea Level (MSL).

Found by correcting CA for density. TA is very important because

terrain elevation on navigational charts is labeled in feet MSL.

Absolute Altitude:

Actual height of the aircraft above the surface of the earth. Also known

as altitude Above Ground Level (AGL).

Figure 4.4-3 shows a comparison of these altitudes.

Figure 4.4-3 Altitudes

4.6-94