[Proj] Terminology: what should I call 60 nautical miles?
Gerald I. Evenden
geraldi.evenden at gmail.com
Mon Apr 27 10:15:04 EST 2009
On Monday 27 April 2009 10:51:16 am Clifford J Mugnier wrote:
Yes, yes, but I believe it is defined as a meridian arc minute and thus only
subject to the minor variation of eccentricty. Of course it now has a legal,
fixed metric length. Its purpose was probably for the navigator to always
have a handy scale at the left or right edge of the chart for measuring
For some unknown reason it is still used by sea/air navigators. Must be
retained as a link to the romantic history of travel. Certainly has no other
> One minute of arc distance at what latitude?
> On a sphere, "longitude varies as the cosine of the latitude" but we're not
> on a sphere, are we?
> This stuff is not complicated enough for lay people now, so we have to add
> another esoteric label to shorten "60 nm?"
> C. Mugnier
> From: proj-bounces at lists.maptools.org on behalf of Gerald I. Evenden
> Sent: Mon 27-Apr-09 09:05
> To: PROJ.4 and general Projections Discussions
> Subject: Re: [Proj] Terminology: what should I call 60 nautical miles?
> On Monday 27 April 2009 7:12:18 am Mikael Rittri wrote:
> > Hello,
> > I would like a term for the length unit that is 60 nautical miles.
> Dare I ask why?
> The "nautical mile" is a rather old fashion term handy in the days of
> sailing on a chart with sextant and chronometer.
> I thought everyone was supposed to go metric---an underachieved effort on
> this side of the pond.
> > This length unit would approximate one degree of
> > arc distance, in the same way as one nautical mile
> > approximates one minute of arc distance.
> > I have thought of the phrase "degree of arc distance"
> > (which I think agrees, more or less, with how Snyder uses this phrase)
> > but some of my colleagues dislike it.
> > I have also thought of the phrase "exentanautical mile",
> > from Greek "exenta" = 60, but...
> > --
> > Mikael Rittri
> > Carmenta AB
> > SWEDEN
> > www.carmenta.com
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