Grad System and Units of Measurement
Date: 08/11/98 at 14:13:53 From: Greg MacNeill Subject: Grad units of measurement Hi, I am having trouble finding information on one mode of operation for a simple scientific calculator. Typically three systems of measurement are provided: deg, rad and grad, which I assume represent degree, radian and grad. As I understand, the grad system is commonly used in Scandinavia and other northern European countries, particularly in mapping. How does the grad system compare to the degree system? Is it true that the grad coordinate system is entirely consistent with metric measurement? Apparently grad units of arc are directly related to the metric linear equivalent. This is not the case of course with degrees except in nautical applications where 1 minute of arc equals 1 nautical mile on the surface of the earth. To achieve uniformity, perhaps we should measure all distances in nautical miles or adopt the grad system for angle measurement. Please let me know what you can about the basics of grad measurement. Thanks, Greg
Date: 08/14/98 at 15:39:27 From: Doctor Schwa Subject: Re: Grad units of measurement Grads are defined to be 100 in a right angle, for people who are obsessed with the decimal system. Grad units of arc are related to the metric system only in that way: a multiple of 10 is used in their definition. The original definition of kilometer was that there are 10,000 of them between the equator and the north pole, so that 1 grad = 100 km, 1 centigrad = 1 km, would indeed be convenient for mapping in much the same way as 1 minute = 1 nautical mile is. But of course that's just an approximation - among other things, the Earth isn't particularly close to a perfect sphere. I side with the Babylonians - the convenience of 90 degrees being evenly divisible by all kinds of things (most notably 3, which makes the 30-60-90 triangle so easy to talk about) is well worth it. - Doctor Schwa, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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