Longitude

[Murthy Yenamandra]

Joe Varo wonders:
> By the way, can anyone tell me what the difference is between a "mile" and
> a "nautical mile".  This is something I've always wondered about but have
> never been able (or willing to look hard enough) to find a satisfactory
> answer.  I know there's a conversion formula for miles to naut. miles, but
> what is the purpose of the difference?

The purpose of the difference is that the nautical mile was formulated
specifically for sea and air navigation, using the dimensions of the
earth, so that it's easier to calculate the distance between where you
are on the sea and where you want to be.

>From the on-line webster:

nautical mile n
(1632)
:any of various units of distance used for sea and air navigation based
     on the length of a minute of arc of a great circle of the earth
     and differing because the earth is not a perfect sphere: as
a: a British unit equal to 6080 feet ([1853] meters) -- called also Admiralty
     mile
b: a U.S. unit no longer in official use equal to 6080.20 feet (1853.248
     meters)
c: an international unit equal to 6076.115 feet (1852 meters) used
     officially in the U.S. since July 1, 1959 

> Is there a metric equivalent, like a "nautical kilometer" or something?

Guess not, unless there is a little-known variant using the metric
angles on earth's circumference.

Murthy

-- 
Murthy Yenamandra, Dept of CompSci, U of Minnesota. mailto:yenamand at cs.umn.edu
    "I'm stubborn as those garbage bags that time can not decay
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