Stanley M. Max
Department of Mathematics, Towson University Towson, Maryland 21252, USA
Even in countries where the International System of Units (SI, the modern metric system) has long been established, knots are used to measure navigational speed on the sea and in the air. This is surprising because a knot, which equals one nautical mile per hour, is not an SI unit of measurement. Both the International Bureau of Weights and Measures (the independent international agency charged with regulating SI) and the International Civil Aviation Organization (the United Nations agency charged with regulating international aviation) decry the use of non-SI units to measure navigational speed. So why are knots used instead of kilometers per hour, which is an SI unit? The reason is that the knot is based upon the size and shape of the Earth, and therefore this unit has natural appeal to navigators. Does a method exist to use kilometers per hour to measure navigational speed that is also based upon the size and shape of the Earth, and which would therefore provide equal appeal to navigators? Yes it does, provided that angular measurement is performed using gradians (also called gons) instead of degrees.
Aviation; Navigation; International System of Units (SI); Metric system; Degrees; Gradians; Gons; Measurement
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