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Gary LaPook writes:

You got that a bit wrong, the meter was originally defined as one ten 
millionth of the distance from the equator to the north pole. The 
nautical mile is the length of one minute of latitude, 5400 between the 
equator and the pole. Since the size and shape of the earth varies none 
of these are accurate at all places on the earth so the choice of the 
length to use for the nautical mile is somewhat arbitrary. It used to be 
defined as 6080 feet but by international agreement it was redefined to 
be exactly 1852 meters, hence 6076.1155 feet, close enough for 
government work.


BTW, going back to first principles, ten million meters divided by 5400 
nautical miles equals 1851.851851851851851851851..... awfully close to 
1852 meters per nautical mile, accurate to 8 one thousandths of one 
percent, .008%


Dan Allen wrote:

>Occasionally you will see a reference to an "Admiralty mile".  In the  
>1800s this was used by England and was 6,080 feet long.
>
>Today England uses a new "nautical mile" and it is a bit shorter at  
>1852 meters exactly, or 6,076.1155 feet long.
>
>Q1:  Does anyone still use the older, slightly large British nautical  
>mile?  Do any parts of England still refer to it?
>
>Q2:  Why was the change made?  Was it part of the move to metric in  
>the 1970s?
>
>I know that the distance of a nautical mile was originally to be  
>1/10,000,000th of the distance from the equator to the poles but  
>early estimates of this distance were out a bit.  Was this an  
>influence on the adoption of a "new" nautical mile?
>
>Dan Allen
>N39.997� W111.757�
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