A program I wrote years ago for use in my hp 67
card-reading calculator using RPN logic

See it below (also works with hp 97 and
hp 41)**The formula is:**
**Z= 62900
log**_{10}**
P**_{o}**/P**
**where Z=altitude in feet, P=Pressure at the
upper limit in any units, and
P**_{o}**=pressure
in same units as above corresponding to zero
altitude.****This works well to 12,000' at middle latitudes, and
assumes a mean temperature of the air column (isothermal
temperature) of 50°f.****Or, to reduce upper station readings to mean sea
level,
use the inverse of the log**

P_{o}= P[10^{x}(Z / 62900)]

Note: This is the old isothermal calibration standard (Bureau of Standards, Circular No.46). It was used to calibrate altimeters for airplanes between 1917 and 1925--before airplanes could fly much over 12,000'.

The old card reader calculator is 25 years old! Alas, I can't update the calculator, so I am bringing myself (kicking and screaming) up to date with Excel! |

for Mac |
Bob, Thanks for the spreadsheet. It works fine. I had to estimate the height of one dam above another dam to see if a windmill could push the water that far uphill. I borrowed an accurate aneroid barometer and using your spreadsheet & the barometer readings I could calculate that the higher dam is 61 metres above the lower dam. Thanks. |

If you want to reduce an upper station elevation reading (adjust your new barometer to the elevation of your house) to its sea level equivalent (which is the way all barometer readings are reported), here is an online converter that works with your browser.

It will also calculate the boiling point of water at any atmospheric pressure, so you will know how to adjust the time your 2-minute egg.

f LBL A ENTER STO 1 STO 6
29.97984 STO 5 RCL 1 RTN f LBL B ENTER 32 - RCL 1 x .0001
x CHS RCL 1 + STO 6 RTN f LBL C ENTER CHS 211.99 + STO
2 18.8 STO 4 29.97984 STO 5 RCL 2 RCL 4 ÷ RCL 3 x
CHS RCL 5 + STO 6 RTN f LBL D ENTER STO 5 RTN (always
enter after LBL A) f LBL E RCL 5 RCL 6 ÷ LOG
62900 x RTN Button
A enters the observed height
of the barometer in "Hg. Button
B enters the temperature of
the thermometer in °f. Button
C enters the observed
boiling point of water in °f. Button
D (optional) modifies the
default mean sea level 29.97984 Hg to a known
value. Button
E solves for altitude in
feet. If you are using Apple's OS X, you can get a
free

10.1184 STO 3

**To
run:**or,

and, if known,

*virtual* **hp41CV**
RPN calculator (a newer classic hp
model) from **nsim**.

Looks and works just like the real deal--fully
programable too. And it runs on your computer
desktop!

I use this a lot, now.

©1999, 2007

Bob Graham