A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Size of a nautical mile
From: Clive Sutherland
Date: 2009 Jan 18, 09:14 -0000
Just a thought, If instead of the canal, putting
in a pipe with a tap and a turbine would this give a perpetual source of power!
[mailto:NavList@fer3.com] On Behalf
Of Peter Fogg
January 2009 22:26
Subject: [NavList 7078] Re: Size
of a nautical mile
Simplicity. That's my understanding; that 1,852m = minute of arc at sea surface was
adopted as being appropriate for practical naviagtion in the zones of
latitude where most nav gets practised - ie; excluding high latitudes around the
When it comes to
precision there is no end to potential discrepancies. After the earth's
oblate shape come the uneven surface of the oceans: there are local hills and
valleys, the Pacific and Atlantic don't share the same levels (one reason the
original, simple through-canal, plan for the Panama Canal was doomed
to failure, as it would have resulted in a non-stop rush of water surging from
one side to the other). The Pacific even has different levels on the
eastern side compared to the western. Each time the level of the sea
changes so does the length of a minute of arc mesured along its surface.
On Fri, Jan 16, 2009 at 8:35 AM, Lu Abel <email@example.com> wrote:
As has been pointed out, the length of a degree of latitude varies from
pole to equator.
The nautical mile is supposed to equal a degree of latitude. Today,
however, it is defined as precisely 1852 meters.
When one multiplies 1852 by 7200 (the number of minutes in 90 degrees),
one gets 10 000 800 meters as an answer.
My understanding is that the distance from equator to pole is 10 002 000
meters. It's a small discrepency, on the order of 0.01%, but I'm
wondering why it was allowed to stand instead of defining the NM more
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