Yes, our "snapshot" of atmospheric pressure and the use of that was a
rather crude tool, yet it served our purposes.
I should have qualified my comments. I've been retired from active duty
for 20 years now (as of the first of this July) and my last submarine
tour of duty was a few years before my retirement. The weather
information sent to us consisted of a "map" of the North Atlantic drawn
on teletype paper using various alphanumeric characters to represent
North American and European coasts (left and right edges of the paper),
low and high pressure centers, and fronts. We also copied weather
information by CW (International Morse Code).
We merely needed a way to maintain a reasonable atmospheric pressure
within the submarine.
Jim
John M. Steele wrote:
That process is exactly what a pilot is doing (below transition to
flight level) when he enters altimeter correction so the airfield will
read the correct height above sea level for landing and takeoff
(particularly in landing, as you aim at the blue in takeoff, and you aim
at the hard in landing).
However, it seems odd you would encode the pressure in the boat as
altitude. Why not use an aneroid barometer and record "station
pressure." Your process memorizes local sea level pressure at an
instant, but it will surely be different the next time you raise the
mast in another time and place.
NWS uses two processes to calculate a "sea level pressure." One uses
the altimeter equation and directly yields the altimeter correction, the
other uses a different assumption about temperature of the air column
between sea level and the station and is preferred for analysis of
highs, lows, weather patterns.
------------------------------------------------------------------------
*From:* James R. Frysinger <j...@metricmethods.com>
*To:* U.S. Metric Association <usma@colostate.edu>
*Sent:* Sun, April 18, 2010 9:50:39 PM
*Subject:* [USMA:47171] Re: Air flight altitudes in meters
Thanks, John. Your knowledge obviously exceeds my faint acquaintance
with this matter.
Now, I HAVE had personal experience with aneroid altimeters, the
pneumo-mechanical sort where the big hand spun a complete circle for
every "one thousand feet" (I think that was the number). We used them on
submarines to measure the "pressure in the boat". (Non-submariners
should call 'em "ships".) Whenever we raised the induction mast to
ventilate (an extremely infrequent event on some missions) we would
"zero" our altimeter readout by adjusting the base pressure knob. As air
bank pressures bled down due to air usage or rose when compressors
charged them back up, that readout would change.
Your experience undoubtedly was ABOVE sea level, though.
Jim
John M. Steele wrote:
> Actually, it is nominally based on height above sealevel. Sitting on
the runway, with altimeter correction dialed in, it will read the
published height of the runway above sealevel.
> At cruise levels, no altimeter correction is used and reading is
called flight level. It is the height above sea level IF sea level were
at 15 °C, 101.325 kPa, and a lapse rate of -6.5 K/km to the stratosphere
(11 km), and zero lapse rate above that to 20 km. Further it it uses a
height variable called geopotential height, the height that would be
true if gravity were constant with height. There is a transformation
between that and geometric height in the standard.
>
> ------------------------------------------------------------------------
> *From:* James R. Frysinger <j...@metricmethods.com
<mailto:j...@metricmethods.com>>
> *To:* U.S. Metric Association <usma@colostate.edu
<mailto:usma@colostate.edu>>
> *Cc:* U.S. Metric Association <usma@colostate.edu
<mailto:usma@colostate.edu>>
> *Sent:* Sun, April 18, 2010 8:47:07 PM
> *Subject:* [USMA:47168] Re: Air flight altitudes in meters
>
>
> Altimeters work off of atmospheric pressure readings, Pat. But the
readout is in terms of height above terrain. So assignments and reports
are always in length units. No human pressure to altitude correlation
procedures are used.
>
> Jim
>
> Pat Naughtin wrote:
> > Dear John, Jim, and All,
> >
> > My understanding is that air craft actually measure pressure in
something like kilopascals and that this pressure measurement is then
changed (dumbed down ?) to a measure that implies that a measure of
length has been made somehow.
> >
> > I suppose you could dangle a mass tied on a piece of string out
the window of the plane so that it drags along the ground, but it sounds
impractical!
> >
> > By the way, some approximate conversions from pressure to height
might go something like this:
> >
> > Pressure
> >
> > >
> > Altitude
> >
> > kilopascal
> >
> > >
> > metres
> >
> > 100
> >
> > >
> > 0
> >
> > 90
> >
> > >
> > 1 000
> >
> > 80
> >
> > >
> > 2 000
> >
> > 70
> >
> > >
> > 3 000
> >
> > 65
> >
> > >
> > 4 000
> >
> > 60
> >
> > >
> > 5 000
> >
> > 45
> >
> > >
> > 6 000
> >
> > 40
> >
> > >
> > 8 000
> >
> > 22
> >
> > >
> > 10 000
> >
> > 19
> >
> > >
> > 12 000
> >
> > 15
> >
> > >
> > 14 000
> >
> > 10
> >
> > >
> > 16 000
> >
> > 7
> >
> > >
> > 18 000
> >
> > 4
> >
> > >
> > 20 000
> >
> > 3
> >
> > >
> > 25 000
> >
> > 1
> >
> > >
> > 30 000
> >
> >
> > Cheers,
> > Pat Naughtin
> > Author of the ebook, /Metrication Leaders Guide,/ that you can
obtain from
http://metricationmatters.com/MetricationLeadersGuideInfo.html PO Box
305 Belmont 3216,
> > Geelong, Australia
> > Phone: 61 3 5241 2008
> >
> > Metric system consultant, writer, and speaker, Pat Naughtin, has
helped thousands of people and hundreds of companies upgrade to the
modern metric system smoothly, quickly, and so economically that they
now save thousands each year when buying, processing, or selling for
their businesses. Pat provides services and resources for many different
trades, crafts, and professions for commercial, industrial and
government metrication leaders in Asia, Europe, and in the USA. Pat's
clients include the Australian Government, Google, NASA, NIST, and the
metric associations of Canada, the UK, and the USA. See
http://www.metricationmatters.com
<http://www.metricationmatters.com/>for more metrication information,
contact Pat at pat.naugh...@metricationmatters.com
<mailto:pat.naugh...@metricationmatters.com>
<mailto:pat.naugh...@metricationmatters.com
<mailto:pat.naugh...@metricationmatters.com>>
<mailto:pat.naugh...@metricationmatters.com
<mailto:pat.naugh...@metricationmatters.com>
<mailto:pat.naugh...@metricationmatters.com
<mailto:pat.naugh...@metricationmatters.com>>> or to get the free
'/Metrication matters/' newsletter go to:
http://www.metricationmatters.com/newsletter to subscribe.
> >
> > On 2010/04/19, at 05:57 , John M. Steele wrote:
> >
> >> It is my understanding that European air space is controlled in feet.
> >> The Wikipedia article on "flight level" shows a metric structure
for Russia, China, Mongolia, North Korea and various CIS States
(non-European former USSR satellites). Everybody else flies in feet (I
think).
> >>
> >>
------------------------------------------------------------------------
> >> *From:* James R. Frysinger <j...@metricmethods.com
<mailto:j...@metricmethods.com> <mailto:j...@metricmethods.com
<mailto:j...@metricmethods.com>> <mailto:j...@metricmethods.com
<mailto:j...@metricmethods.com> <mailto:j...@metricmethods.com
<mailto:j...@metricmethods.com>>>>
> >> *To:* U.S. Metric Association <usma@colostate.edu
<mailto:usma@colostate.edu> <mailto:usma@colostate.edu
<mailto:usma@colostate.edu>> <mailto:usma@colostate.edu
<mailto:usma@colostate.edu> <mailto:usma@colostate.edu
<mailto:usma@colostate.edu>>>>
> >> *Sent:* Sun, April 18, 2010 3:13:10 PM
> >> *Subject:* [USMA:47149] Air flight altitudes in meters
> >>
> >>
> >> My impression had been that all air flight altitudes were given
and heeded in terms of feet. But this article implies flight altitudes
in meters.
> >>
http://www.foxnews.com/world/2010/04/17/european-skies-largely-remain-fly-zone/
> >>
> >> Jim
> >>
> >> -- James R. Frysinger
> >> 632 Stony Point Mountain Road
> >> Doyle, TN 38559-3030
> >>
> >> (C) 931.212.0267
> >> (H) 931.657.3107
> >> (F) 931.657.3108
> >>
> >
>
> -- James R. Frysinger
> 632 Stony Point Mountain Road
> Doyle, TN 38559-3030
>
> (C) 931.212.0267
> (H) 931.657.3107
> (F) 931.657.3108
>
-- James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
