# Node (unit)

Physical unit | |
---|---|

Unit name | node |

Unit symbol | |

Physical quantity (s) | speed |

Formula symbol | |

dimension | |

In SI units | |

Named after | Knot (tying) |

Derived from | Nautical mile , hour |

The **knot** (kn) is a measure of speed in sea and aviation or meteorology , which is based on the unit of length nautical mile ( *sm* ) or nautical mile ( *NM, nmi, n.mi.* ). One nautical mile is exactly 1852 meters . The unit symbol is kn (English formerly *kt* ).

**1 knot** = 1 nautical mile per hour

## Origin and use

The name is derived from the knots that are made in the line of the log to mark certain distances. The distances are ideally a fraction of a nautical mile. The number of knots that are covered in a certain time results in the so-called ride through water ( *FdW* ). The time was set by the log glass , a special hourglass.

Nowadays, this journey through the water is determined much more precisely by other logging systems (hydrostatic, hydrodynamic, electric, etc.). What is more important for navigation , however, is the ground speed , which is determined either with other navigation aids such as GNSS , terrestrial navigation, radio navigation or by taking the ocean current into account .

The **nautical mile** or **nautical mile** (German: **sm** , English: **NM** ) corresponds to a difference in geographical latitude of one angular minute (1 '), and thus 60 nautical miles correspond to one degree of latitude . A ship traveling exactly north or south at a speed of 20 knots covers one degree of latitude in three hours.

## conversion

### Exactly

The conversion of knots into nautical miles per hour, nautical miles per hour, kilometers per hour , meters per minute and in meters per second :

### Roughly

An easy-to-remember rule of thumb for converting knots into kilometers per hour is: "Times two, minus 10%" (or "minus 10%, times two").

The rough conversion as a formula:

The error in this calculation is less than 3%.

## See also

- Thread (unit of length)
- Beaufort scale (wind speed)