This page documents an OPTIMADE Unit Definition. See https://schemas.optimade.org/ for more information.

**ID: https://schemas.optimade.org/defs/v1.2/units/si/general/knot**

`knot`

**Unit name:** knot

**Latin symbol:** knot

**Display symbol:** knot

**Description:** A unit of speed primarily used in navigation defined as 1 nautical mile per hour which is equal to (1852/3600) m/s using the current, or one of the historical, definitions of the SI units.

The knot unit appears in the International System of Units (SI), 1st ed. (1970) defined as "1 nautical mile per hour = (1852/3600) m/s."

- The International System of Units (SI), 1st ed. (1970) categorizes the unit as "Units in use temporarily with the International System."
- The International System of Units (SI), 7th ed. (1998) changes the categorization to "Other non-SI units currently accepted for use with the International System."
- The International System of Units (SI), 8th ed. (2006) changes the categorization to "Other non-SI units."
- The knot is omitted in the International System of Units (SI), 9th Edition (2019).

The knot unit was implicitly redefined via the redefinition of the metre at the 17th CGPM meeting (1983), resolution 1.

This is a generalized definition taken to reference the current, or one of the historical, SI unit definitions. This definition is intended for situations when it is not possible to be more precise, e.g., in contexts where data have been collected that uses different historical SI definitions.

**Resources:**

- Definition in the International System of Units (SI), 1st Edition
- Redefinition of the metre at the 17th CGPM meeting (1983), resolution 1
- Wikipedia article describing the unit

**Compatibility:** (other definitions that are covered by the above definition)

`https://schemas.optimade.org/defs/v1.2/units/si/1970/temporary/knot`

`https://schemas.optimade.org/defs/v1.2/units/si/1983/temporary/knot`

**JSON definition:**

```
{
"$id": "https://schemas.optimade.org/defs/v1.2/units/si/general/knot",
"$schema": "https://schemas.optimade.org/meta/v1.2/optimade/physical_unit_definition.json",
"title": "knot",
"symbol": "knot",
"display-symbol": "knot",
"description": "A unit of speed primarily used in navigation defined as 1 nautical mile per hour which is equal to (1852/3600) m/s using the current, or one of the historical, definitions of the SI units.\n\nThe knot unit appears in the International System of Units (SI), 1st ed. (1970) defined as \"1 nautical mile per hour = (1852/3600) m/s.\"\n\n- The International System of Units (SI), 1st ed. (1970) categorizes the unit as \"Units in use temporarily with the International System.\"\n- The International System of Units (SI), 7th ed. (1998) changes the categorization to \"Other non-SI units currently accepted for use with the International System.\"\n- The International System of Units (SI), 8th ed. (2006) changes the categorization to \"Other non-SI units.\"\n- The knot is omitted in the International System of Units (SI), 9th Edition (2019).\n\nThe knot unit was implicitly redefined via the redefinition of the metre at the 17th CGPM meeting (1983), resolution 1.\n\nThis is a generalized definition taken to reference the current, or one of the historical, SI unit definitions.\nThis definition is intended for situations when it is not possible to be more precise, e.g., in contexts where data have been collected that uses different historical SI definitions.",
"compatibility": [
"https://schemas.optimade.org/defs/v1.2/units/si/1970/temporary/knot",
"https://schemas.optimade.org/defs/v1.2/units/si/1983/temporary/knot"
],
"resources": [
{
"relation": "Definition in the International System of Units (SI), 1st Edition",
"resource-id": "https://www.bipm.org/en/publications/si-brochure"
},
{
"relation": "Redefinition of the metre at the 17th CGPM meeting (1983), resolution 1",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/17-1983/resolution-1"
},
{
"relation": "Wikipedia article describing the unit",
"resource-id": "https://en.wikipedia.org/wiki/Knot_(unit)"
}
],
"defining-relation": {
"base-units": [
{
"symbol": "m",
"id": "https://schemas.optimade.org/defs/v1.2/units/si/general/metre"
},
{
"symbol": "s",
"id": "https://schemas.optimade.org/defs/v1.2/units/si/general/second"
}
],
"base-units-expression": "ms^-1",
"scale": {
"numerator": 1852,
"denominator": 3600
}
},
"x-optimade-definition": {
"label": "knot_si_general",
"kind": "unit",
"format": "1.2",
"version": "1.2.0",
"name": "knot"
}
}
```