Package org.orekit.utils.units

Class Unit

java.lang.Object
org.orekit.utils.units.Unit
All Implemented Interfaces:
Serializable
public class Unit extends Object implements Serializable
Basic handling of multiplicative units.

This class is by no means a complete handling of units. For complete support, look at libraries like UOM. This class handles only time, length, mass and current dimensions, as well as angles (which are dimensionless).

Instances of this class are immutable.

Since:
11.0
Author:
Luc Maisonobe
See Also:

  • Field Details

    • NONE

      public static final Unit NONE
      No unit.

    • ONE

      public static final Unit ONE
      Dimensionless unit.

    • CYCLE

      public static final Unit CYCLE
      Cycle unit.
      Since:
      13.0

    • PERCENT

      public static final Unit PERCENT
      Percentage unit.

    • SECOND

      public static final Unit SECOND
      Second unit.

    • MINUTE

      public static final Unit MINUTE
      Minute unit.

    • HOUR

      public static final Unit HOUR
      Hour unit.

    • DAY

      public static final Unit DAY
      Day unit.

    • YEAR

      public static final Unit YEAR
      Julian year unit.
      See Also:

    • HERTZ

      public static final Unit HERTZ
      Hertz unit.

    • METRE

      public static final Unit METRE
      Metre unit.

    • KILOMETRE

      public static final Unit KILOMETRE
      Kilometre unit.

    • KILOGRAM

      public static final Unit KILOGRAM
      Kilogram unit.

    • GRAM

      public static final Unit GRAM
      Gram unit.

    • AMPERE

      public static final Unit AMPERE
      Ampere unit.

    • RADIAN

      public static final Unit RADIAN
      Radian unit.

    • DEGREE

      public static final Unit DEGREE
      Degree unit.

    • ARC_MINUTE

      public static final Unit ARC_MINUTE
      Arc minute unit.

    • ARC_SECOND

      public static final Unit ARC_SECOND
      Arc second unit.

    • REVOLUTION

      public static final Unit REVOLUTION
      Revolution unit.

    • NEWTON

      public static final Unit NEWTON
      Newton unit.

    • PASCAL

      public static final Unit PASCAL
      Pascal unit.

    • BAR

      public static final Unit BAR
      Bar unit.

    • JOULE

      public static final Unit JOULE
      Joule unit.

    • WATT

      public static final Unit WATT
      Watt unit.

    • COULOMB

      public static final Unit COULOMB
      Coulomb unit.

    • VOLT

      public static final Unit VOLT
      Volt unit.

    • OHM

      public static final Unit OHM
      Ohm unit.

    • TESLA

      public static final Unit TESLA
      tesla unit.

    • SOLAR_FLUX_UNIT

      public static final Unit SOLAR_FLUX_UNIT
      Solar Flux Unit.

    • TOTAL_ELECTRON_CONTENT_UNIT

      public static final Unit TOTAL_ELECTRON_CONTENT_UNIT
      Total Electron Content Unit.

    • EARTH_RADII

      public static final Unit EARTH_RADII
      Earth Radii used as Bstar unit in CCSDS OMM.

  • Constructor Details

    • Unit

      public Unit(String name, double scale, Fraction mass, Fraction length, Fraction time, Fraction current, Fraction angle)
      Simple constructor.
      Parameters:
      name - name of the unit
      scale - scaling factor to SI units
      mass - mass exponent
      length - length exponent
      time - time exponent
      current - current exponent
      angle - angle exponent

  • Method Details

    • getName

      public String getName()
      Get the name of the unit.
      Returns:
      name of the unit

    • getScale

      public double getScale()
      Get the scaling factor to SI units.
      Returns:
      scaling factor to SI units

    • getMass

      public Fraction getMass()
      Get the mass exponent.
      Returns:
      mass exponent

    • getLength

      public Fraction getLength()
      Get the length exponent.
      Returns:
      length exponent

    • getTime

      public Fraction getTime()
      Get the time exponent.
      Returns:
      time exponent

    • getCurrent

      public Fraction getCurrent()
      Get the current exponent.
      Returns:
      current exponent

    • getAngle

      public Fraction getAngle()
      Get the angle exponent.
      Returns:
      angle exponent

    • sameDimension

      public boolean sameDimension(Unit other)
      Check if a unit has the same dimension as another unit.
      Parameters:
      other - other unit to check against
      Returns:
      true if unit has the same dimension as the other unit

    • sameDimensionSI

      public Unit sameDimensionSI()
      Create the SI unit with same dimension.
      Returns:
      a new unit, with same dimension as instance and scaling factor set to 1.0

    • ensureCompatible

      public static void ensureCompatible(String description, List<Unit> reference, boolean allowScaleDifferences, List<Unit> units)
      Ensure some units are compatible with reference units.
      Parameters:
      description - description of the units list (for error message generation)
      reference - reference units
      allowScaleDifferences - if true, unit with same dimension but different scale (like KILOMETRE versus METRE) are allowed, otherwise they will trigger an exception
      units - units to check
      Throws:
      OrekitException - if units are not compatible (number of elements, dimensions or scaling)

    • alias

      public Unit alias(String newName)
      Create an alias for a unit.
      Parameters:
      newName - name of the new unit
      Returns:
      a new unit representing same unit as the instance but with a different name

    • scale

      public Unit scale(String newName, double factor)
      Scale a unit.
      Parameters:
      newName - name of the new unit
      factor - scaling factor
      Returns:
      a new unit representing scale times the instance

    • power

      public Unit power(String newName, Fraction exponent)
      Create power of unit.
      Parameters:
      newName - name of the new unit
      exponent - exponent to apply
      Returns:
      a new unit representing the power of the instance

    • sqrt

      public Unit sqrt(String newName)
      Create root of unit.
      Parameters:
      newName - name of the new unit
      Returns:
      a new unit representing the square root of the instance

    • multiply

      public Unit multiply(String newName, Unit other)
      Create product of units.
      Parameters:
      newName - name of the new unit
      other - unit to multiply with
      Returns:
      a new unit representing the this times the other unit

    • divide

      public Unit divide(String newName, Unit other)
      Create quotient of units.
      Parameters:
      newName - name of the new unit
      other - unit to divide with
      Returns:
      a new unit representing the this divided by the other unit

    • toSI

      public double toSI(double value)
      Convert a value to SI units.
      Parameters:
      value - value instance unit
      Returns:
      value in SI units

    • toSI

      public double toSI(Double value)
      Convert a value to SI units.
      Parameters:
      value - value instance unit
      Returns:
      value in SI units

    • toSI

      public <T extends CalculusFieldElement<T>> T toSI(T value)
      Convert a value to SI units.
      Type Parameters:
      T - type of the field elements
      Parameters:
      value - value instance unit
      Returns:
      value in SI units
      Since:
      12.1

    • fromSI

      public double fromSI(double value)
      Convert a value from SI units.
      Parameters:
      value - value SI unit
      Returns:
      value in instance units

    • fromSI

      public double fromSI(Double value)
      Convert a value from SI units.
      Parameters:
      value - value SI unit
      Returns:
      value in instance units

    • fromSI

      public <T extends CalculusFieldElement<T>> T fromSI(T value)
      Convert a value from SI units.
      Type Parameters:
      T - type of the field elements
      Parameters:
      value - value SI unit
      Returns:
      value in instance units

    • parse

      public static Unit parse(String unitSpecification)
      Parse a unit.

      The grammar for unit specification allows chains units multiplication and division, as well as putting powers on units.

      The symbols used for units are the SI units with some extensions.

      year
      the accepted non-SI unit for Julian year is "a" but we also accept "yr"
      day
      the accepted non-SI unit for day is "d" but we also accept "day"
      dimensionless
      both "1" and "#" (U+0023, NUMBER SIGN) are accepted
      mass
      "g" is the standard symbol, despite the unit is "kg" (it is the only unit that has a prefix in its name, so all multiples must be based on "g")
      degrees
      the base symbol for degrees is "°" (U+00B0, DEGREE SIGN), but we also accept "◦" (U+25E6, WHITE BULLET) and "deg"
      arcminute
      The base symbol for arcminute is "′" (U+2032, PRIME) but we also accept "'" (U+0027, APOSTROPHE)
      arcsecond
      The base symbol for arcsecond is "″" (U+2033, DOUBLE PRIME) but we also accept "''" (two occurrences of U+0027, APOSTROPHE), "\"" (U+0022, QUOTATION MARK) and "as"

      All the SI prefix (from "y", yocto, to "Y", Yotta) are accepted, as well as integer prefixes. The standard symbol for micro 10⁻⁶ is "µ" (U+00B5, MICRO SIGN), but we also accept "μ" (U+03BC, GREEK SMALL LETTER MU). Beware that some combinations are forbidden, for example "Pa" is Pascal, not peta-years, and "as" is arcsecond for this parser, not atto-seconds, because many people in the space field use mas for milliarcseconds and µas for microarcseconds. Beware that prefixes are case-sensitive! Integer prefixes can be used to specify units like "30s", but only once at the beginning of the specification (i.e. "2rev/d²" is accepted, but "rev/(2d)²" is refused). Conforming with SI brochure "The International System of Units" (9th edition, 2019), each SI prefix is part of the unit and precedes the unit symbol without a separator (i.e. MHz is seen as one identifier).

      multiplication
      can specified with either "*" (U+002A, ASTERISK), "×" (U+00D7, MULTIPLICATION SIGN), "." (U+002E, FULL STOP) or "·" (U+00B7, MIDDLE DOT) as the operator
      division
      can be specified with either "/" (U+002F, SOLIDUS) or "⁄" (U+2044, FRACTION SLASH) as the operator
      powers
      can be specified either by
      • prefixing with the unicode "√" (U+221A, SQUARE ROOT) character
      • postfixing with "**", "^" or implicitly using unicode superscripts

      Exponents can be specified in different ways:

      • as an integer, as in "m^-2" or "m⁻²"
      • directly as unicode characters for the few fractions that unicode supports, as in "Ω^⅞"
      • as the special decimal value 0.5 which is used by CCSDS, as in "km**0.5"
      • as a pair of parentheses surrounding two integers separated by a solidus or fraction slash, as in "Pa^(11/12)"
      For integer exponents, the digits must be ASCII digits from the Basic Latin block from unicode if explicit exponent marker "**" or "^" is used, or using unicode superscript digits if implicit exponentiation (i.e. no markers at all) is used. Unicode superscripts are not allowed for fractional exponents because unicode does not provide a superscript solidus. Negative exponents can be used too.

      These rules mean all the following (silly) examples are parsed properly: MHz, km/√d, kg.m.s⁻¹, µas^⅖/(h**(2)×m)³, km/√(kg.s), km**0.5, 2rev/d²

      Parameters:
      unitSpecification - unit specification to parse
      Returns:
      parsed unit

    • equals

      public boolean equals(Object unit)
      Check if the instance represents the same unit as another instance.

      The name is not considered so aliases are considered equal.

      Overrides:
      equals in class Object
      Parameters:
      unit - other unit
      Returns:
      true if the instance and the other unit refer to the same unit

    • hashCode

      public int hashCode()
      Get a hashcode for this unit.
      Overrides:
      hashCode in class Object
      Returns:
      hashcode

    • toString

      public String toString()
      Overrides:
      toString in class Object