arcminute, ′ (unit)

{
    "$id": "https://schemas.optimade.org/defs/v1.2/units/si/1970/accepted/arcminute",
    "$schema": "https://schemas.optimade.org/meta/v1.2/optimade/physical_unit_definition.json",
    "title": "arcminute",
    "symbol": "arcmin",
    "display-symbol": "\u2032",
    "alternate-symbols": [
        "minute of arc",
        "minute of angle",
        "MOA",
        "'"
    ],
    "description": "A unit of plane and phase angle equal to 1/60 of a degree which is 1/21600 of a circle and equivalent to pi/10800 rad, with rad defined according to the 1960 supplementary SI unit.\n\nThis definition uses \"arcminute\" as the unit name to distinguish it from the time unit named minute.\nA footnote in the International System of Units, 9th ed. (2019) note that \"arcsecond is an alternative name for second of plane angle\".\nHowever, \"arcminute\" and \"arcmin\" have so far not been mentioned in any of the editions of the International System of Units.\nThey are defined in the GNU Units 3.15 unit database as 1/60 degree.\n\nThe unit appear under the name minute (with symbol \u2032) in the International System of Units (SI), 1st ed. (1970) defined as \"1\u2032 = (1/60)\u00b0 = (\u03c0/10800) rad\".\n\n- The International System of Units (SI), 1st ed. (1970) categorizes the unit as \"Units in use with the International System.\"\n- The International System of Units (SI), 7th ed. (1998) adds as a footnote: \"ISO 31 recommends that the degree be subdivided decimally rather than using the minute and second.\"\n- The International System of Units (SI), 8th ed. (2006) further adds to that footnote: \"For navigation and surveying, however, the minute has the advantage that one minute of latitude on the surface of the Earth corresponds (approximately) to one nautical mile.\"\n- The International System of Units (SI), 9th ed. (2019) replaces the footnote with: \"For some applications such as in astronomy, small angles are measured in arcseconds (i.e. seconds of plane angle), denoted as or \u2032\u2032, or milliarcseconds, microarcseconds and picoarcseconds, denoted mas, \u03bcas and pas, respectively, where arcsecond is an alternative name for second of plane angle.\"\n- The formulation \"denoted as or \u2033\" is reproduced here faithfully from the source and suggests an alternate symbol may have been omitted due to a typographical error.\n  It is not clear what alternate symbol was intended to be referenced.",
    "resources": [
        {
            "relation": "Definition in the International System of Units (SI), 1st Edition",
            "resource-id": "https://www.bipm.org/en/publications/si-brochure"
        },
        {
            "relation": "Wikipedia article describing the unit",
            "resource-id": "https://en.wikipedia.org/wiki/Minute_and_second_of_arc"
        }
    ],
    "defining-relation": {
        "base-units": [
            {
                "symbol": "pi",
                "id": "https://schemas.optimade.org/defs/v1.2/constants/math/basic/pi"
            },
            {
                "symbol": "rad",
                "id": "https://schemas.optimade.org/defs/v1.2/units/si/1960/supplementary/radian"
            }
        ],
        "base-units-expression": "pi*rad",
        "scale": {
            "denominator": 10800
        }
    },
    "x-optimade-definition": {
        "label": "arcminute_si_1970_accepted",
        "kind": "unit",
        "format": "1.2",
        "version": "1.2.0",
        "name": "arcminute"
    }
}