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January 5th 05, 07:32 AM
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"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 |
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