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Re: [Phys-l] Atmospheric pressure calculus deduction



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