"Mark Zenier" wrote
In article hqdCd.13035$622.3888@lakeread02,
Jack Painter wrote:
"Joel Rubin" wrote
On Sun, 2 Jan 2005 09:03:24 -0500, "HankG" wrote:
Just curious. Anyone know what the longest GC distance from any point
on
Earth to any other point?
Of course, the original definition (not the current definition) of the
meter was 1/10-millionth of the distance between the north pole and
the quator. So, presumably, the distance from pole to pole is 20
million meters or 20,000 km.
The earth is not quite a sphere - I believe the equator is slightly
longer than a circle of longitude.
I was not aware there was ever any intention to make a kilometer
relational
to a nautical mile. It is not, and is just as arbitrary a length of
measurement in relationship to a nautical mile (which derives from the
spherical geometry of all modern positioning) as the statute (English)
mile.
Metric arithmetic is certainly easier (for humans, computers could care
less) than statute miles. But both are arbitrary as far as latitude and
longitude are concerned and each require an equal effort of arithmetic to
convert to nautical miles. Air and marine charts use nautical miles for
this
reason.
Duh. The nautical mile is tied to the babylonian units for angle.
(1 minute of arc on the earths surface is one nautical mile.
Which arc they used varied, so different countries nautical miles
were a bit different).
The metric system uses the Grad, where the circle is divided into.
400 units.
1 Grad of Latitude = 100 km.
I thought the military used Grads, but maybe that's just Army Artillery.
Mark Zenier Washington State resident
"DUH" ??? (you sure you're not Canadian?)
Artillery is not navigation. The Army changed to metric because it couldn't
teach arithmetic that didn't use the 10-fingers/10-toes concept. All well
and good except that left it with no way to make the kilometer into anything
relational to the earth or navigational geometry, which it has neither in
common with. Hence the GRAD, which does NOT refer to having completed more
than six GRADES, or knowing anything about navigation. If you're trying to
get somewhere over the horizon instead of hitting it with a howitzer, then
reading "Practical Navigation:" by Bowditch will be much more useful than
anything the Army taught you.
Hooo-Awww
Jack Painter
Virginia Beach, Virginia