# Nautical mile

**nautical milesnmnmi.nmimilemilesnautical-mileMsquare nautical milegeographical miles**

A nautical mile is a unit of measurement used in both air and marine navigation, and for the definition of territorial waters.wikipedia

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### Minute and second of arc

**masarcsecondarc second**

Historically, it was defined as one minute (1⁄60 of a degree) of latitude along any line of longitude.

The nautical mile was originally defined as a minute of latitude on a hypothetical spherical Earth so the actual Earth circumference is very near 21 600 nautical miles.

### Knot (unit)

**knotsknotkn**

The derived unit of speed is the knot, one nautical mile per hour.

The knot is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.15078 mph or 0.514 m/s).

### Latitude

**latitudesSouthlatitudinal**

Historically, it was defined as one minute (1⁄60 of a degree) of latitude along any line of longitude. 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.

The length of 1 minute of latitude is 1.853 km (1.00 nautical miles), while the length of 1 second of latitude is 30.8 m (see nautical mile).

### International Civil Aviation Organization

**ICAOICAO recommendations on use of the International System of UnitsInternational Civil Aviation Organization (ICAO)**

### Earth's circumference

**circumference of the Earthcircumference of EarthEquatorial circumferences**

The Earth's circumference is therefore approximately 40,000 km.

In modern times, Earth's circumference has been used to define fundamental units of measurement of length: the nautical mile in the seventeenth century and the metre in the eighteenth.

### Conversion of units

**conversion factorunit conversionConversions**

### Equator

**equatorial plane0°The Equator**

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 1861 metres at the poles and 1843 metres at the Equator.

The IUGG standard meridian is, to the nearest millimetre, 40007.862917 km, one arc-minute of which is 1852.216 m, explaining the SI standardization of the nautical mile as 1852 m, more than 3 m less than the geographical mile.

### Degree (angle)

**°degreesdegree**

In the early 1600s English mathematician Edmund Gunter proposed that 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.

Maritime charts are marked in degrees and decimal minutes to facilitate measurement; 1 minute of latitude is 1 nautical mile.

### Geographical mile

**mile (geographical)miles**

The equatorial circumference is slightly longer than the polar circumference – the measurement based on this (40,075.017 km × 1⁄60 × 1⁄360 = 1855.3 metres) is known as the geographical mile.

The geographical mile is slightly larger than the nautical mile (which was historically linked to the circumference measured through both poles); one geographic mile is equivalent to approximately 1855.3 m.

### Cable length

**cablescablecables length**

A cable length or length of cable is a nautical unit of measure equal to one tenth of a nautical mile or approximately 100 fathoms.

### Metre

**metermmetres**

The metre was originally defined as 1⁄10,000,000 of the meridian arc from the North pole to the equator passing through Dunkirk.

### Mile

**miRoman milemiles**

The word mile is from the Latin word for a thousand paces: mille passus.

### Unit of measurement

**unitunits of measurementweights and measures**

A nautical mile is a unit of measurement used in both air and marine navigation, and for the definition of territorial waters.

### Navigation

**nauticalnavigatenavigational**

A nautical mile is a unit of measurement used in both air and marine navigation, and for the definition of territorial waters.

### Territorial waters

**territorial seacoastal waterscontiguous zone**

A nautical mile is a unit of measurement used in both air and marine navigation, and for the definition of territorial waters.

### Longitude

**WestlongitudinalE**

Historically, it was defined as one minute (1⁄60 of a degree) of latitude along any line of longitude. 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.

### International Hydrographic Organization

**IHOInternational Hydrographic OrganisationInternational Hydrographic Bureau**

### Institute of Electrical and Electronics Engineers

**IEEEFellow of the Institute of Electrical and Electronics EngineersTechnical Field Award**

### United States Government Publishing Office

**Government Printing OfficeUnited States Government Printing OfficeU.S. Government Printing Office**

### Latin

**Latin languageLat.la**

The word mile is from the Latin word for a thousand paces: mille passus.

### Coordinate system

**coordinatescoordinateaxis**

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.

### Circle of latitude

**parallelparallelscircles of latitude**

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.

### Meridian (geography)

**meridianmeridiansmeridian line**

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.

### Edmund Gunter

**Gunter ruleGunter's scaleGunter's rule**

In the early 1600s English mathematician Edmund Gunter proposed that 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.