Re: [Phys-l] Atmospheric pressure calculus deduction

[John Denker <jsd@av8n.com>]

On 06/17/2008 06:45 AM, Pete Lohstreter wrote:

> The equation is derived from standard values and can be seen at....
> <http://wahiduddin.net/calc/density_altitude.htm>   [1]

Another discussion of the basic physics can be found at:
  http://www.av8n.com/physics/altimetry.htm           [2]

 -- It includes more-general formulas, valid in all of the ISA
  atmosphere, not just the troposphere.  It shows the connection
  between the official FAA altimetry formulas and the ISA model.
  It explains why even though the formulas look complicated, the 
  Kollsman correction takes a remarkably simple form, just an
  additive altitude shift.

 -- OTOH unlike reference [1] it doesn't bother to quantify the 
  humidity correction.


Note that an altimeter tells you the altitude, given the pressure.
In contrast, if you're interested in the reverse problem, namely 
finding the pressure given your altitude (and atmospheric conditions),
a well-commented program to do that is at
  http://www.av8n.com/physics/barometry.html