Well, I guess if one is going very low and slow (for example, a surface
vessel at 20 or so knots) and can take "half a day" to get a fix (a known
position), the difference is not very important, but at 600+ knots it can
become a little more significant. Your NROTC instructor was making it
easier for you by rounding a nautical mile down to 6000 feet from 6076.10
feet as stated on page 2-5 of Air Navigation Manual (AFM 51-40, NAVAIR
00-80V-49, dated 1 Jul 73). ;<))))))) For me, it has been rounded up to
6080 feet for 50 years.
Other definitions of a nautical mile in the same paragraph: One minute of
arc of a great circle on a sphere having an area equal to that of the earth.
One minute of arc on the earth's equator (geographic mile) - 6087.08 feet.
One minute of arc on a meridian - one minute of latitude. Two thousand
yards for short distances, i. e., very low and very slow. ;<)))
Wilton
----- Original Message -----
From: "Max Dillon" <meadedil...@bellsouth.net>
To: "'Mercedes Discussion List'" <mercedes@okiebenz.com>
Sent: Sunday, June 05, 2011 12:05 PM
Subject: [MBZ] OT global obesity alarm
When I was taught navigation in NROTC back in nineteen hundred and
ninety-one, one nautical mile was 2000 yards, or 6000 feet, or one minute
of
arc of latitude. I can only assume that the earth must have gained some
girth, increasing the size of one minute of arc by 80 feet.
Someone tell the global warming folks about the new threat - global
obesity,
whereby fuel consumption decreases and time slows down, costing our
economy
billions! Soon we won't even be able to reach Europe, let alone
Australia!
Oh the horror!
-Max
-----Original Message-----
From: mercedes-boun...@okiebenz.com [mailto:mercedes-boun...@okiebenz.com]
On Behalf Of WILTON
Sent: Saturday, June 04, 2011 11:29 PM
To: Mercedes Discussion List
Subject: Re: [MBZ] speed
Technically, yes, but the difference is negligible in the range of
altitudes
traveled by surface vessels and aircraft. International convention has
accepted and established a knot as one nautical mile (6080 feet - one
minute
of arc of latitude) per hour.
Wilton
----- Original Message -----
From: "Mitch Haley" <m...@voyager.net>
To: "Mercedes Discussion List" <mercedes@okiebenz.com>
Sent: Saturday, June 04, 2011 9:21 PM
Subject: Re: [MBZ] speed
MG wrote:
Wilton, wouldn't that be only measured at sea level? I would think that
as you go higher in altitude that one minute of arc would get longer.
Now
mind I'm only thinking back to my school days and that circle and pie
wedge thing in beginning geometry.
Remember that a circumference is 2pi x radius. So flying five nautical
miles high makes the whole lap around the globe 10pi miles longer. That
extra 31.4 nautical miles adds 31.4 / 21600 = .00015 nautical miles or
.88
feet or 10.6" to each mile in order to keep the minute of arc thing
straight. That's a lot less than the difference between ground speed and
airspeed.
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