Mike,

On Thu, 16 Sep 2004 09:38:22 -0500, Mike Hord wrote:

> I'm looking for a good, no-nonsense explanation of the variation of
> pressure with altitude.

To sum up, as long as you stay below about 20,000ft, pressure reduces by 1hPa (formerly millibar) per 10 metre 
rise in altitude.  Sorry about the mixture of units, but this is what I can remember!

Don't forget that atmospheric pressure varies with the weather, and I've seen it fall really fast when a 
serious Low comes in - I seem to remember 1hPa in 40 minutes, so don't discount this if there's a really 
strong wind!
 
> Basically what I want to know is this:  can I use a pressure
> sensor with an absolute range of up to 30 PSI to measure within
> 10 to 20 feet the difference in altitude between the current position
> of a sensor package and the position at which the package was
> initialized?  At altitudes of 1000 feet or less?

Yes, but the pressure change isn't very large - about 0.004psi over ten feet.

Cheers,


Howard Winter
St.Albans, England


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