Public Domain Aeronautical Software (PDAS)

The equations used are those adopted 15 October 1976 by the
United States Committee on Extension to the Standard Atmosphere
(COESA), representing 29 U.S. scientific and engineering
organizations. The values selected in 1976 are slight modifications
of those adopted in 1962. The equations and parameters used are
documented in a book entitled
U.S. Standard Atmosphere, 1976
published by the U.S. Government Printing Office, Washington, D.C.

#### The Fundamental 7 layers of the Standard Atmosphere to 86
km

h1 and h2 are geopotential altitude in kilometers of
the lower and upper boundaries of a layer.
The gradient dT/dH is kelvins per kilometer.

h1(km) |
h2(km) |
dT/dh (K/km) |

0 |
11 |
-6.5 |

11 |
20 |
0.0 |

20 |
32 |
1.0 |

32 |
47 |
2.8 |

47 |
51 |
0.0 |

51 |
71 |
-2.8 |

71 |
84.852 |
-2.0 |

Note: 84.852 km geopotential=86 km geometric

These data along with the sea level standard values of

Sea level pressure = 101325 N/m^{2}

Sea level temperature = 288.15 K

Hydrostatic constant = 34.1631947 kelvin/km

define the atmosphere.
The sea level density of 1.225
kg/m^{3} is derived from the fundamental quantities above.

#### So where do the values of pressure in the Atmosphere Routine
Come From?

The values of pressure at the boundaries between layers are not an
explicit part of the standard because they are derivable from the
values of temperature gradient and the hydrostatic equations.
If you want to see how the pressures were computed, I have made the
computing program and its results available.

For more information, go to the National Space Science Data
Center
(NSSDC) description of the 1976 atmosphere.

You may read the page describing the hydrostatic equations.
XHTML+MathML, 12KB or
PDF, 69KB.