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From: David.Smith@cmu-cs-ius.arpa
Newsgroups: net.space
Subject: Nautical miles
Message-ID: <12155@sri-arpa.UUCP>
Date: Tue, 10-Apr-84 12:06:28 EST
Article-I.D.: sri-arpa.12155
Posted: Tue Apr 10 12:06:28 1984
Date-Received: Sun, 15-Apr-84 09:13:22 EST
Lines: 15


	Why are the distances, speeds, etc. measured in terms of nautical
	miles?  Why not statute miles?  For that matter, why not kilometers?

It is time-honored navigational practice.  Given the coordinates of origin
and destination, spherical trigonometry can be used to produce the arc
length between them, expressed in angular measure (vertex of angle at center
of earth).  This arc is historically measured in degrees, minutes, and
seconds.  The nautical mile is defined to be one arc-minute over the surface
of the earth.

I will tiptoe quietly away from the question of how the earth's oblateness
is handled.

			David Smith