# Node (unit)

Physical unit
Unit name node
Unit symbol ${\ displaystyle \ mathrm {kn}}$ Physical quantity (s) speed
Formula symbol ${\ displaystyle v}$ dimension ${\ displaystyle {\ mathsf {L \; T ^ {- 1}}}}$ In SI units ${\ displaystyle \ mathrm {1 \, kn = {\ frac {463 \; m} {900 \; s}} = 0 {,} 51 ​​{\ overline {4}} \; {\ frac {m} {s }}}}$ 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 :

${\ displaystyle 1 \, \ mathrm {kn} = 1 \, \ mathrm {\ frac {sm} {h}} = 1 \, \ mathrm {\ frac {NM} {h}} = 1 {,} 852 \ , \ mathrm {\ frac {km} {h}} = 30 {,} 8 {\ overline {6}} \, \ mathrm {\ frac {m} {min}} = 0 {,} 51 ​​{\ overline { 4}} \, \ mathrm {\ frac {m} {s}}}$ ### 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").

${\ displaystyle v \ left [\ mathrm {kn} \ right] \ rightarrow \ times 2 \ rightarrow -10 \, \% = v \ left [{\ frac {\ mathrm {km}} {\ mathrm {h}} } \ right]}$ The rough conversion as a formula:

${\ displaystyle v \, \ mathrm {kn} \ approx 2 \ cdot v \ cdot 0 {,} 9 \, {\ frac {\ mathrm {km}} {\ mathrm {h}}}}$ The error in this calculation is less than 3%.