Re: Barometric altimeter calibration

From: Gary S. (Idontwantspam_at_net)
Date: 07/29/04 

Date: Thu, 29 Jul 2004 18:14:51 GMT

On Thu, 29 Jul 2004 11:55:17 -0500, "the Moderator"
<sparky@no_spam_engineer.com> wrote:

>"Umberto Uderzo" <uuderzo@togli.infinito.it> wrote in message
>news:opsbwpm7vzhb7hfm@ubi...
>> Oh, now I understand, I think...
>>
>> So the barometric pressure I must know where I'm standing still must be
>> the sea level pressure.
>> But now the question is... How can I find a sea level pressure measurement
>> on a mountain refuge
>> at 3000mt altitude?
>>
>> It seems to me that this way to calibrate the altimeter is only a
>> theorical way...
>>
>The barometric pressure that the weatherman gives is the barometric pressure
>at sea level.
>
Often, but not always.

In New England, they often include the weather station on the summit
of Mt. Washington in NH (6288'). The barometric pressure given is
usually 23" of Hg more or less, while sea level pressure is usually
30" of Hg more or less.

In that case they may give the reading off their instruments at
whatever altitude the station happens to be.

I verified by looking at weather reports from cities at higher
altitude, Denver for example, and comparing that to a coastal city,
Boston in this case. The numbers were comparable (about 30") for both
today, although I am not experiencing Denver area weather. Actually,
based purely on altitude without correction, Denver barometer readings
would be about 25" Hg.

The OP may find this helpful
<http://www.wrh.noaa.gov/Saltlake/projects/wxcalc/formulas/stationPressure.pdf>
and
<http://www.wrh.noaa.gov/Saltlake/projects/wxcalc/formulas/pressureAltitude.pdf>

and other items on this page:
<http://www.wrh.noaa.gov/Saltlake/projects/wxcalc/wxcalc.html>

An airport would give pilots a standardized sea level pressure for
calibrating their instruments prior to takeoff.

Happy trails,
Gary (net.yogi.bear)
------------------------------------------------
at the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

Relevant Pages

  • Re: Barometric altimeter calibration
    ... >>The barometric pressure that the weatherman gives is the barometric ... they often include the weather station on the summit ... > usually 23" of Hg more or less, while sea level pressure is usually ... > based purely on altitude without correction, Denver barometer readings ...
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