<Li> nm (the SI symbol for the nanometre) is used by the U.S. National Oceanic and Atmospheric Administration . </Li> <Li> nmi is used by the Institute of Electrical and Electronics Engineers and the United States Government Publishing Office . </Li> <P> While using M itself, the International Bureau of Weights and Measures recognises that NM, Nm and nmi are also in use . </P> <P> The word mile is from the Latin word for a thousand paces: mille passus . Navigation at sea was done by eye until around 1500 when navigational instruments were developed and cartographers began using a coordinate system with parallels of latitude and meridians of longitude . In 1617 the Dutch scientist Willebrord Snell assessed the circumference of the Earth at 24,630 Roman miles (24,024 statute miles). Around that time British mathematician Edmund Gunter improved navigational tools including a new quadrant to determine latitude at sea . He reasoned that the lines of latitude could be used as the basis for a unit of measurement for distance and proposed the nautical mile as one minute or one - sixtieth (1 / 60) of one degree of latitude . As one degree is 1 / 360 of a circle, one minute of arc is 1 / 21600 of a circle (or, in radians, π / 10800). These sexagesimal (base 60) units originated in Babylonian astronomy . Gunter used Snell's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude . Since the earth is not a perfect sphere but is an oblate spheroid with slightly flattened poles, a minute of latitude is not constant, but about 1,861 metres at the poles and 1,843 metres at the Equator, with a mean value of 1,852.3 metres (6,077 ft). Other countries measure the minute of arc at 45 degrees latitude, giving the nautical mile a length of 6076 ft (approximately 1852 m). </P>

What is the earth circumference in nautical miles