Re: Barometric altimeter calibration

From: the Moderator (sparky_at_no_spam_engineer.com)
Date: 07/29/04 

Date: Thu, 29 Jul 2004 13:43:48 -0500

"Gary S." <Idontwantspam@net> wrote in message
news:4aeig0ti3betliu20nkr0rsta4ks9smh9a@4ax.com...
> 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.p
df>
> 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

I stand by my statement. Local weathermen report barometric readings at sea
level even if all the land in the broadcast area is above sea level. To do
otherwise is of no value. If specific barometric readings are given for
specific altitudes that is one thing, but weathermen in Colorado are not
reporting the barometric reading at Denver's altitude. They report the
barometric pressure at sea level.

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