The Standard Atmosphere Model is a hypothetical Vertical Distribution of Atmospheric Temperature, pressure, and density which, by International agreement, is taken to be representative of the atmosphere for purposes of Pressure altimeter calibrations, Aircraft performance calculations, aircraft and Rocket Design, Ballistic Tables, and other related uses. It assumes a Mean sea level temperature of 15°C, a Standard lapse rate of 6.5°C per kilometer up to the tropopause at 11 km, and various other Standard Conditions.