
=head1 NAME

Image::ExifTool::MIEUnits - MIE units documentation

=head1 DESCRIPTION

The MIE format allows units of measurement to be specified in brackets at
the end of a MIE tag name (eg. "Volume(m3)"). This document describes the
standard MIE units abbreviations.

=head1 SYNTAX

The units string may contain any ASCII characters in the range 0x21 ('!') to
0x7d ('}'), excepting the bracket characters (0x28 and 0x29).  An empty
string is allowed, and indicates a dimensionless value.  L<Standard
units|/STANDARD UNITS> should be used where possible.  In the standard
units, an underline ('_') is used to indicate a subscript, and multiple
words may be separated with a hyphen ('-').

Exponents should be positive, and require no separator (eg. "m2" for square
meters).  L<Prefixes|/PREFIXES> may be added to the standard units (eg.
"cm") except when the resulting name conflicts with another standard unit.

Multiplication is indicated by '.', and division by '/'.  Reciprocal units
(ie. the multiplicative inverse) are obtained through division rather than
the use of negative exponents (eg. "/in", not "in-1").  In MIE units,
multiplication has precedence over division, so everything to the right of a
'/' is in the denominator.  (See L</EXAMPLES> for a few examples.)

Below is a table summarizing the special characters used in MIE units
strings.

  .           multiplication
  /           division (used for negative exponents)
  -           word separator
  _           subscript
  {}          annotation
  []          used to avoid name conflicts if necessary
  0-9         exponentiation

=head1 STANDARD UNITS

              dimensionless
  [G]         Newtonian constant of gravitation (unclassified)
  [g]         standard acceleration of free fall (acceleration)
  [h]         Planck constant (action)
  [k]         Boltzmann constant (unclassified)
  {cfu}       colony forming units (number)
  {rbc}       red blood cell count (number)
  {tbl}       tablets (number)
  {tot}       particles total count (number)
  %           percent (fraction)
  10^N        the number ten for arbitrary powers (number)
  A           Ampere (electric current)
  a           year (time)
  a_g         mean Gregorian year (time)
  a_j         mean Julian year (time)
  a_t         tropical year (time)
  acr         acre, U.S. (area)
  acr_br      acre, British (area)
  Ao          Angstrom (length)
  APL-U       APL unit (biologic activity of anticardiolipin IgA)
  ar          are (area)
  arb-U       arbitrary unit (arbitrary)
  arcmin      minute of arc (plane angle)
  arcsec      second of arc (plane angle)
  atm         standard atmosphere (pressure)
  att         technical atmosphere (pressure)
  AU          astronomic unit (length)
  b           barn (action area)
  B           bel (level)
  B-kW        bel kilowatt (power level)
  B-mV        bel millivolt (electric potential level)
  B-SPL       bel sound pressure (pressure level)
  B-uV        bel microvolt (electric potential level)
  B-V         bel volt (electric potential level)
  B-W         bel watt (power level)
  bar         bar (pressure)
  bbl         barrel (fluid volume)
  Bd          baud (signal transmission rate)
  bdsk-U      Bodansky unit (biologic activity of phosphatase)
  beth-U      Bethesda unit (biologic activity of factor VIII inhibitor)
  bf          board foot (volume)
  Bi          Biot (electric current)
  bit         bit (amount of information)
  Bq          Becquerel (radioactivity)
  Btu         British thermal unit (energy)
  Btu_39      British thermal unit at 39 degF (energy)
  Btu_59      British thermal unit at 59 degF (energy)
  Btu_60      British thermal unit at 60 degF (energy)
  Btu_IT      international table British thermal unit (energy)
  Btu_m       mean British thermal unit (energy)
  Btu_th      thermochemical British thermal unit (energy)
  bu          bushel, U.S. (dry volume)
  bu_br       bushel, British (volume)
  By          byte (amount of information)
  C           Coulomb (electric charge)
  c           velocity of light (velocity)
  cal         calorie (energy)
  Cal         nutrition label Calories (energy)
  cal_15      calorie at 15 degC (energy)
  cal_20      calorie at 20 degC (energy)
  cal_IT      international table calorie (energy)
  cal_m       mean calorie (energy)
  cal_th      thermochemical calorie (energy)
  car_Au      carat of gold alloys (mass fraction)
  car_m       metric carat (mass)
  cd          candela (luminous intensity)
  Cel         degree Celsius (temperature)
  Ch          Charriere (gauge of catheters)
  ch          Gunter's chain, U.S. (length)
  ch_br       Gunter's chain, British (length)
  Ci          Curie (radioactivity)
  cicero      cicero (length)
  circ        circle (plane angle)
  cml         circular mil, international (area)
  cr          cord, international (volume)
  crd_us      cord, U.S. (fluid volume)
  cup_us      cup (volume)
  d           day (time)
  deg         degree (plane angle)
  deg{mag}    degree from magnetic north (plane angle)
  degF        degree Fahrenheit (temperature)
  didot       didot (length)
  diop        diopter (refraction of a lens)
  dpt         dry pint, U.S. (dry volume)
  dqt         dry quart, U.S. (dry volume)
  dr          dram (mass)
  dr_ap       dram, apothecary (mass)
  drp         drop (volume)
  dye-U       Dye unit (biologic activity of amylase)
  dyn         dyne (force)
  e           elementary charge (electric charge)
  eps_0       permittivity of vacuum (electric permittivity)
  eq          equivalents (amount of substance)
  erg         erg (energy)
  eV          electronvolt (energy)
  F           Farad (electric capacitance)
  fdr         fluid dram, U.S. (fluid volume)
  fdr_br      fluid dram, British (volume)
  foz         fluid ounce, U.S. (fluid volume)
  foz_br      fluid ounce, British (volume)
  ft          foot, international (length)
  ft_br       foot, British (length)
  ft_us       foot, U.S. (length)
  fth         fathom, international (length)
  fth_br      fathom, British (length)
  fth_us      fathom, U.S. (length)
  fur         furlong, U.S. (length)
  G           Gauss (magnetic flux density)
  g           gram (mass)
  g.m/{H-B}   gram meter per heartbeat (prop. to ventricular stroke work)
  g%          gram percent (mass fraction)
  Gal         Gal (acceleration)
  gal         gallon, U.S. (fluid volume)
  gal_br      gallon, British (volume)
  gal_wi      historical winchester gallon (dry volume)
  Gb          Gilbert (magnetic tension)
  gf          gram-force (force)
  gil         gill, U.S. (fluid volume)
  gil_br      gill, British (volume)
  gon         gon (plane angle)
  GPL-U       GPL unit (biologic activity of anticardiolipin IgG)
  gr          grain (mass)
  Gy          Gray (energy dose)
  H           Henry (inductance)
  h           hour (time)
  hd          hand, international (height of horses)
  hnsf-U      Hounsfield unit (x-ray attenuation)
  HP          horsepower (power)
  hp_C        homeopathic potency of centesimal series (homeopathic potency)
  hp_X        homeopathic potency of decimal series (homeopathic potency)
  HPF         high power field (view area in microscope)
  Hz          Herz (frequency)
  in          inch, international (length)
  in_br       inch, British (length)
  in_us       inch, U.S. (length)
  in-H2O      inch of water column (pressure)
  in-Hg       inch of mercury column (pressure)
  iU          international unit (arbitrary)
  J           Joule (energy)
  K           Kelvin (temperature)
  ka-U        King-Armstrong unit (biologic activity of phosphatase)
  kat         katal (catalytic activity)
  kg{wet-tis} kilogram of wet tissue (mass)
  kn          knot, international (velocity)
  kn_br       knot, British (velocity)
  knk-U       Kunkel unit (arbitrary biologic activity)
  Ky          Kayser (lineic number)
  l           liter (volume)
  L           liter (volume)
  lb          pound (mass)
  lb_ap       pound, apothecary (mass)
  lb_tr       pound, troy (mass)
  lbf         pound force (force)
  lcwt        long hunderdweight (mass)
  ligne       ligne (length)
  lk          link for Gunter's chain, U.S. (length)
  lk_br       link for Gunter's chain, British (length)
  lm          lumen (luminous flux)
  Lmb         Lambert (brightness)
  lne         line (length)
  LPF         low power field (view area in microscope)
  lton        long ton (mass)
  lx          lux (illuminance)
  ly          light-year (length)
  m           meter (length)
  m_e         electron mass (mass)
  m_p         proton mass (mass)
  m-H2O       meter of water column (pressure)
  m-Hg        meter of mercury column (pressure)
  mclg-U      Mac Lagan unit (arbitrary biologic activity)
  mesh        mesh, international (lineic number)
  MET         metabolic equivalent (metabolic cost of physical activity)
  mg{creat}   milligram of creatinine (mass)
  mho         mho (electric conductance)
  mi          mile, international (statute mile) (length)
  mi_br       mile, British (length)
  mi_us       mile, U.S. (length)
  mil         mil, international (length)
  mil_us      mil, U.S. (length)
  min         minute (time)
  min_br      minim, British (volume)
  min_us      minim, U.S. (fluid volume)
  mo          month (time)
  mo_g        mean Gregorian month (time)
  mo_j        mean Julian month (time)
  mo_s        synodal month (time)
  mol         mole (amount of substance)
  MPL-U       MPL unit (biologic activity of anticardiolipin IgM)
  mu_0        permeability of vacuum (magnetic permeability)
  Mx          Maxwell (flux of magnetic induction)
  N           Newton (force)
  nmi         nautical mile, international (length)
  nmi_br      nautical mile, British (length)
  Np          neper (level)
  Oe          Oersted (magnetic field intensity)
  Ohm         Ohm (electric resistance)
  osm         osmole of dissolved particles (amount of substance)
  oz          ounce (mass)
  oz_ap       ounce, apothecary (mass)
  oz_tr       ounce, troy (mass)
  P           Poise (dynamic viscosity)
  Pa          Pascal (pressure)
  pc          parsec (length)
  pc_br       pace (length)
  pca         pica (length)
  pca_pr      Printer's pica (length)
  pH          pH (acidity)
  ph          phot (illuminance)
  pi          the number pi (number)
  pied        pied (length)
  pk          peck, U.S. (dry volume)
  pk_br       peck, British (volume)
  pnt         point (length)
  pnt_pr      Printer's point (length)
  pouce       pouce (length)
  ppb         parts per billion (fraction)
  ppm         parts per million (fraction)
  ppth        parts per thousand (fraction)
  pptr        parts per trillion (fraction)
  PRU         peripheral vascular resistance unit (fluid resistance)
  psi         pound per square inch (pressure)
  pt          pint, U.S. (fluid volume)
  pt_br       pint, British (volume)
  pwt_tr      pennyweight (mass)
  qt          quart, U.S. (fluid volume)
  qt_br       quart, British (volume)
  R           Roentgen (ion dose)
  rad         radian (plane angle)
  RAD         radiation absorbed dose (energy dose)
  rch         Ramden's chain, U.S. (length)
  rd          rod, U.S. (length)
  rd_br       rod, British (length)
  REM         radiation equivalent man (dose equivalent)
  rlk_us      link for Ramden's chain (length)
  s           second (time)
  S           Siemens (electric conductance)
  sb          stilb (lum. intensity density)
  sc_ap       scruple, apothecary (mass)
  sct         section (area)
  scwt        short hundredweight (mass)
  smgy-U      Somogyi unit (biologic activity of amylase)
  sph         spere (solid angle)
  sr          streadian (solid angle)
  st          stere (volume)
  St          Stokes (kinematic viscosity)
  ston        short ton (mass)
  stone       stone (mass)
  Sv          Sievert (dose equivalent)
  Sv-U        Svedberg unit (sedimentation coefficient)
  T           Tesla (magnetic flux density)
  t           tonne (mass)
  tb-U        tuberculin unit (biologic activity of tuberculin)
  tbs         tablespoon, U.S. (volume)
  todd-U      Todd unit (biologic activity antistreptolysin O)
  tsp         teaspoon, U.S. (volume)
  twp         township (area)
  u           unified atomic mass unit (mass)
  U           Unit (catalytic activity)
  USP-U       U.S. Pharmacopeia unit (arbitrary)
  V           Volt (electric potential)
  W           Watt (power)
  Wb          Weber (magnetic flux)
  wk          week (time)
  yd          yard, international (length)
  yd_br       yard, British (length)
  yd_us       yard, U.S. (length)

=head1 PREFIXES

Standard SI prefixes:

  y           yocto (10^-24)
  z           zepto (10^-21)
  a           atto  (10^-18)
  f           femto (10^-15)
  p           pico  (10^-12)
  n           nano  (10^-9)
  u           micro (10^-6)
  m           milli (10^-3)
  c           centi (10^-2)
  d           deci  (10^-1)
  da          deka  (10)
  h           hecto (10^2)
  k           kilo  (10^3)
  G           giga  (10^9)
  M           mega  (10^6)
  T           tera  (10^12)
  P           peta  (10^15)
  E           exa   (10^18)
  Z           zetta (10^21)
  Y           yotta (10^24)

Binary power prefixes:

  Ki          kibi  (2^10)
  Mi          mebi  (2^20)
  Gi          gibi  (2^30)
  Ti          tebi  (2^40)

=head1 EXAMPLES

A few examples of combined units strings:

  /cm3        per cubic centimeter
  in2         square inches
  kg.m/s2     Newtons (N)
  m3/kg.s2    units of [G]
  10^100      googols

=head1 HISTORY

  2006-12-14 - PH Created

=head1 AUTHOR

Copyright 2003-2025, Phil Harvey (philharvey66 at gmail.com)

This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

=head1 REFERENCES

=over 4

=item L<http://aurora.regenstrief.org/UCUM/>

=back

=head1 SEE ALSO

L<Image::ExifTool::MIE(3pm)|Image::ExifTool::MIE>,
L<Image::ExifTool(3pm)|Image::ExifTool>

=cut
