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.

Stanley M. Max. A Theoretical Justification for Using the International System of Units to Measure Navigational Speed.  International Journal of New Developments in Engineering and Society (2017) Vol.1, Num.3: 91-96.

[1]Alder, K. (2002). The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World. Free Press: Little, Brown.
[2]Boyne, W. J. (1987). The Smithsonian Book of Flight. Washington DC: Smithsonian Books.
[3]Bureau International des Poids et Mesures (2006). The International System of Units (SI) (8th ed.). Paris. Retrieved from http:// -www.bipm.org/en/publications/si-brochure/

[4]Crease, R. P. (2011). World in the Balance: The Historic Quest for an Absolute System of Measurement (1st ed.). New York: W.W. Norton.

[5]International Civil Aviation Organization (2017). Retrieved from https://www.icao.int/publications/-Pages/doc7300.aspx

[6]International Civil Aviation Organization (2010). Annex 5 to the Convention on International Civil Aviation: Units of Measure to Be Used in Air and Ground Operations (5th ed.). Montreal. Cited in https://www.icao.int/isbn/Lists/Publications/-DispForm.aspx?ID=1522 and retrieved from http://aerosavvy.com/wp-
content/uploads/2014/08/an05_cons.pdf

[7]Klein, H. A. (1974). The World of Measurements: Masterpieces, Mysteries, and Muddles of Metrology. New York: Simon & Schuster.

[8]Phelps, M. (2013). Flight: 100 Greatest Aircraft. San Francisco: Weldon Owen.

[9]Robinson, A. (2007). The Story of Measurement. New York: Thames & Hudson.
[10]Rowlett, R. (2017). “gon (g)” In How Many? A Dictionary of Units of Measurement. Retrieved from https://www.unc.edu/rowlett/units/dictG.html
[11]Shanghai Cooperation Organisation [sic]. (n.d.) In Wikipedia. Retrieved from https:// -en.wikipedia.org/wiki/Shanghai_Cooperation_Org anisation
[12]Sobel, D. (1995). Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. New York: Walker Publishing.
[13]Texas Instrument (2005, 2010). TI-89 Titanium. Texas Instruments, Inc. Retrieved from https://education.ti.com/en/guidebook/details/en/F A1DC891957E4700B46A67255850C592/89ti
[14]Texas Instrument (2010-2016). Getting Started with the TI-Nspire CX / TI-Nspire CX CAS Handheld. Texas Instruments, Inc. Retrieved from https://education.ti.com/en/guidebook/details/en/-502A552F7D6E4756A75BD8482FEB0E26/-gettingstartedwiththeti-nspirecxhandheld
[15]Thompson, A. & Taylor B. N. (2008). Guide for the Use of the International System of Units (SI)(NIST Special Publication 811 2008 ed.). Washington,DC. Retrieved from https://www.nist.gov/publications/guide-use-international-system-units-si
[16]Tyner, J. A. (2010). Principles of Map Design. New York: Guilford Press.
[17]U.S. Metric Association (2017). Retrieved from http://www.us-metric.org/

[18]Williams, J. H. (2014). Defining and Measuring Nature: The Make of All Things. San Rafael, CA: Morgan and Claypool.

[19]Zupko, R. E. (1990). Revolution in Measurement: Western European Weights and Measures since the Age of Science. Philadelphia, American Philosophical Society.