Altitude

In aerospace engineering there are several definitions of altitude:

h_g- geometric altitude : physical height above sea-level

h_a- absolute altitude : height measured from center of earth

h_geo- geopotential altitude using variable g in the pressure height equation

where r_E is the radius of the earth

h_p- pressure altitude : height from the standard atmosphere table corresponding to the same value of pressure

: usually indicated by the mechanical altimeter

h_T- temperature altitude : height from the standard atmosphere table corresponding to the same value of outside air temperature read on aircraft

= density altitude : height from standard atmosphere table corresponding to the same value of density (calculated using pressure and temperature reading along with the equation of state) - important for computing aerodynamic information at flight condition.