metric system newsgroup call for votes #1

Gene Nygaard wrote
The problem is comparing two imperial to
metric conversion factors that are not as
precise as they could be.

So those aren't definitions after all.

They are definitions. We just have to accept that:
1 UK knot = (1 UK nautical mile + 172 mm) per hour


Exactly what did they learn in 1995 which made them
think that 1853 m is better than the 1852 m adopted
by ... everybody

The value of 1852 m is also adopted by the UK. The definition of the
'UK nautical mile' of 1853 m is for interpretation of historical text
written in the time before the UK accepted the international value.


Exactly what did they learn in 1995 which made them
think that 1853 m is better than the 6080 British ft
the British had adopted

1. The nautical mile is supposed to provide an approximation of 1
minute of angle.
2. Because of non-spherical abberations of the earth, the
approximation can be wrong by tens of metres. Anyone that attempts to
obtain more precise distances could get into big trouble if they do
not know that.
3. The international value is based on the average over the whole
planet.
4. The UK value is calculated in a different way. I seem to remember
it being the value in the English channel, but do not quote me. So
1853 m might actually be nearer to the true value than 1853.172 m
5. Given that the true value at any point varies by tens of metres,
they may have rejected the idea of maintaining mm precision. The
question then becomes why did they abandon the precise relationship
with the knot.

Just some thoughts.


But while the old Admiralty mile could be expressed
exactly with only 7 digits, they redefined one with
only 4 digits.

Quite. I really don't know the answer.

"Pat Norton" wrote in message
...
Gene Nygaard wrote
The problem is comparing two imperial to

1853 m might actually be nearer to the true value than 1853.172 m
5. Given that the true value at any point varies by tens of metres,
they may have rejected the idea of maintaining mm precision. The
question then becomes why did they abandon the precise relationship
with the knot.

Of course, only an technocrat would want to make mm measurements over a
minute of arc. It is as though Gene's mother is also his aunt.