Studied by 13 peopleis the altitude above the surface, also know as, AGL. Above Ground Level.
Absolute altitude
is the actual distance above mean sea level, or, MSL.
True altitude
altitude corrected for non-standard day pressure. It is the altitude that is indicated when the altimeter is set to standard pressure (29.92 "Hg). Needed for most performance tables/charts.
Pressure altitude
altitude corrected for non-standard day pressure AND non- standard day temperature.
Density altitude
altitude read directly from the altimeter (uncorrected) when it is set to the current altimeter setting.
Indicated altitude
