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From: Mike Maurice (no email)
Date: Mon Nov 01 2004 - 12:07:48 EST
At 11:23 AM 11/1/04 -0500, you wrote:
>Assuming spherical earth, we all know that 1 minute of latitude is equal to
>1 nautical mile.
>
>At what latitude is 1 minute of LONGITUDE:
>
> (easy one) equal to 1 nautical mile
> (hard one) equal to 1 STATUTE mile
I don't have Bowditch in front of me.
At an absolute level of precision you can't assume a spherical earth. After
all it ain't so.
One minute of latitude equals one nautical mile. But the tricky part is how
many feet is that. It so happens that as the precision of our measurements
has improved the actual number has changed by a few feet, in some cases by
a few inches. As I recall the number of feet is calculated by the size of
the earth using the latitude and is directly related to the measurement as
it exists and is not necessarily static.
Whereas the statue mile is static.
Fortunately, the level of precision involved is not necessary for ordinary
mariners, or we would be in bi_G trouble.
The details for all this used to be, but may not be in the present version
of Bowditch.
Mike
Capt. Mike Maurice
Tualatin(Portland), Oregon
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