Re: Talking of old jokes

On 2 Jul 2006 10:04:43 -0700, "mike weber"
<fairportfan@xxxxxxxxx> wrote:

Wilson Heydt wrote:
In article <e86jv2$2u4$1@xxxxxxxxxxxxxxxx>,
Keith F. Lynch <kfl@xxxxxxxxxxxxxx> wrote:
Wilson Heydt <whheydt@xxxxxxxxxxx> wrote:
One minute of arc is damned sloppy sextant work. They're accurate
to 6 seconds of arc. A good navigator (using sextant, mechanical
clock, and ephemeris) can get a position at sea to within 1 nautical
mile.

One nautical mile *is* (at least) one minute of arc.

At 45 degrees latittude.

Nope -- at the equator [or any other Great Circle] (damned close,
anyway):

Sea mile = 6000 feet, statute mile = 5280 feet.

Circumference of Earth: 24900 statute miles = 21912 sea miles

Divided by 21600 minutes of arc = 1.014 nautical miles.

Error of 86 feet.

Not quite:

Admiralty Mile (the UK nautical mile until 1970): 6080 feet.

US nautical mile (until 1954): 6080.2 feet.

International nautical mile, as agreed by treaty in 1929, and
since adopted by all nations: 1852 meters, or 6076.1155 feet.
.

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