Several types of aviation altitude:
Indicated altitude is the reading on the altimeter when the altimeter is set to the local barometric pressure at Mean Sea Level.
Absolute altitude is the height of the aircraft above the terrain over which it is flying. Also referred to feet/metres Above Ground Level (AGL).
True altitude is the elevation above mean sea level. (see QNH)
Height is the elevation above a ground reference point, commonly the terrain elevation. (see QFE)
Pressure altitude is the elevation above a standard datum air-pressure plane (typically, 1013.25 millibars or 29.92″ Hg and 15°C).
Pressure altitude and indicated altitude are the same when the altimeter is set to 29.92″ Hg or 1013.25 millibars.
Density altitude is the altitude corrected for non-ISA International Standard Atmosphere atmospheric conditions. Aircraft performance depends on density altitude, which is affected by barometric pressure, humidity and temperature. On a very hot day, density altitude at an airport (especially one at a high elevation) may be so high as to preclude takeoff, particularly for helicopters or a heavily loaded aircraft.
These types of altitude can be explained more simply as various ways of measuring the altitude:
Indicated altitude what the altimeter says
Absolute altitude altitude in terms of the distance above the ground directly below it
True altitude altitude in terms of elevation above sea level
Height altitude in terms of the distance above a certain point
Pressure altitude altitude in terms of the air pressure
Density altitude altitude in terms of the density of the air
si revisas conceptos como ATMÓSFERA ESTANDAR y en PERFORMANCES así como ALTIMETRÍA creo que tus dudas se disiparan.
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