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ISO 80000 3

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ISO 80000-3:2006 is an ISO standard entitled Quantities and units – Part 3: Space and time, superseding ISO 31-1 and ISO 31-2. It is a part of the group of standards called ISO/IEC 80000, which together form the International System of Quantities.

Contents

Contents list

The standard is divided into the following chapters:

  • Foreword
  • Introduction
    1. Scope
    2. Normative references
    3. Names, symbols and definitions
  • Annex A (informative) Units in the CGS system with special names
  • Annex B (informative) Units based on the foot, pound, second, and some other related units
  • Annex C (informative) Other non-SI units given for information, especially regarding the conversion factors
  • Space

    ISO 80000-3:2006 assigns names and symbols to quantities and units of space and time, and defines these quantities and units. For example,

    Units of length, area and volume
  • metre (symbol m): "length of the path travelled by light in vacuum during a time interval of 1/(299 792 458) of a second."
  • Other units of distance defined by the standard are the ångström (symbol Å) (10−10 m) and the nautical mile (1852 m). No symbol is given for the nautical mile.

    The are (symbol a) is a unit of area equal to 100 square metres.

    The litre (symbol L or l) is a unit of volume equal to 10−3 m3.

    Units of angle
  • radian
  • degree of arc: π/180 radians
  • minute of arc: 1/60 degrees of arc
  • second of arc: 1/60 minutes of arc
  • gon: π/200 rad
  • Quantities
  • curvature: χ = 1/ρ, where ρ = radius of curvature
  • area
  • volume
  • angle: α = s/r, where s = length of arc of a circle and r = radius of the circle
  • solid angle
  • Time

    ISO 80000-3:2006 assigns names and symbols to quantities and units of space and time, and defines these quantities and units. For example,

    Units of time, speed and acceleration
  • second (symbol s): "duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom"
  • Other units of time defined by the standard include the minute (1 min = 60 s), the hour (1 h = 60 min) and the day (1 d = 24 h). The year (1 a = 365 d or 366 d) is defined in an informative annex.

  • knot (symbol kn): one nautical mile per hour = 1852/3600 m/s ≈ 0.514 444 m/s.
  • Quantities

    The standard acceleration of free fall is 9.806 65 m/s2.

    Logarithmic quantities and units

    Units of level defined by ISO 80000-3:2006 are:

  • neper: 1 Np = ln(e) = 1
  • bel: 1 B = ln(√10) Np ≈ 1.1512925464970228420089957273422 Np
  • decibel: 1 dB = 0.1 B
  • Annex A (informative)

    The following CGS units are deprecated:

  • The gal (CGS unit of acceleration, equal to 1 cm/s2)
  • Annex B (informative)

    The following non-SI units are deprecated by the standard:

  • The inch (Imperial unit of distance, equal to 25.4 mm)
  • The foot (Imperial unit of distance, equal to 12 inches)
  • The yard (Imperial unit of distance, equal to 3 feet)
  • The mile (Imperial unit of distance, equal to 1760 yards)
  • The acre (Imperial unit of area, equal to 4840 square yards)
  • Annex C (informative)

    The following non-SI units are given for conversion. They are not deprecated by the standard:

  • Units of distance: light year (the distance travelled in one year by light in vacuum; abbreviation l.y.; 1 l.y. ≈ 9,460 730 × 1015 m), astronomical unit (the mean distance of the Earth from the Sun, 1 ua ≈ 1,495 978 706 91(30) × 1011 m), parsec (the distance at which 1 ua subtends an angle of 1 " (second of arc); 1 pc ≈ 206 264,8 ua ≈ 30,856 78 × 1015 m)
  • Units of time: year (a), equal to either 365 days or 366 days
  • References

    ISO 80000-3 Wikipedia