IFC基本单位定义（basic unit declaration）
IFC基本单位定义（basic unit declaration）
单位定义是为了度量具体量的数值表示什么意义。
measures和values
IfcProject定义全局单位
实例一：
// 基本用法
#1=IFCPROJECT (’00ZhrqZYLBcgy$rVVaiu2A’, $, ’Example project’, $, $, $, $, $, #2);
#2=IFCUNITASSIGNMENT ((#3, #4, #5, #6));
#3=IFCSIUNIT (*, .LENGTHUNIT., .MILLI., .METRE.);
#4=IFCSIUNIT (*, .AREAUNIT., $, .SQUARE_METRE.);
#5=IFCSIUNIT (*, .VOLUMEUNIT., $, .CUBIC_METRE.);
#6=IFCSIUNIT (*, .TIMEUNIT., $, .SECOND.);
实例二：
// In a conversion based unit the scaling factor, like 0.0283168466 for cubic feet, expresses how many base units make up one conversion based unit.
#1=IFCPROJECT (’00ZhrqZYLBcgy$rVVaiu2B’, $, ’Example project’, $, $, $, $, $, #2);
#2=IFCUNITASSIGNMENT ((#6, #7, #10, #13));
#3=IFCSIUNIT (*, .LENGTHUNIT., .MILLI., .METRE.);
#4=IFCSIUNIT (*, .AREAUNIT., $, .SQUARE_METRE.);
#5=IFCSIUNIT (*, .VOLUMEUNIT., $, .CUBIC_METRE.);
#6=IFCSIUNIT (*, .TIMEUNIT., $, .SECOND.);
#7=IFCCONVERSIONBASEDUNIT(#9, .LENGTHUNIT., ’INCH’, #8);
#8=IFCMEASUREWITHUNIT(IFCLENGTHMEASURE(25.4), #3);
#9=IFCDIMENSIONALEXPONENTS(1, 0, 0, 0, 0, 0, 0);
#10=IFCCONVERSIONBASEDUNIT(#11, .AREAUNIT., ’SQUARE_FEET’, #12);
#11=IFCDIMENSIONALEXPONENTS(2, 0, 0, 0, 0, 0, 0);
#12=IFCMEASUREWITHUNIT(IFCAREAMEASURE(0.09290304), #4);
#13=IFCCONVERSIONBASEDUNIT(#14, .VOLUMEUNIT., ’CUBIC_FEET’, #15);
#14=IFCDIMENSIONALEXPONENTS(3, 0, 0, 0, 0, 0, 0);
#15=IFCMEASUREWITHUNIT(IFCVOLUMEMEASURE(0.0283168466), #5);
实例三：
// IfcConversionBasedUnitWithOffset is a unit which is converted from another unit by applying a conversion factor and an offset.
#1=IfcConversionBasedUnitWithOffset(
IfcDimensionalExponents(0, 0, 0, 0, 1, 0, 0),
THERMODYNAMICTEMPERATUREUNIT,
'Fahrenheit',
IfcMeasureWithUnit(
IfcThermodynamicTemperatureMeasure(1.8),
IfcSiUnit(THERMODYNAMICTEMPERATUREUNIT, ?, KELVIN)),
-459.67);
实例四：
// An example definition of a unit for specific heat capacity (Joule / kg Kelvin), which is defined as a derived unit based on basic SI units
#1=IFCPROJECT(’00ZhrqZYLBcgy$rVVaiu2A’, $, ’Example project’, $, $, $, $, $, #2);
#2=IFCUNITASSIGNMENT((#3, #4, #5, #6, #7, #8, #9, #10));
#3=IFCSIUNIT(*, .LENGTHUNIT., .MILLI., .METRE.);
#4=IFCSIUNIT(*, .AREAUNIT., $, .SQUARE_METRE.);
#5=IFCSIUNIT(*, .VOLUMEUNIT., $, .CUBIC_METRE.);
#6=IFCSIUNIT(*, .TIMEUNIT., $, .SECOND.);
#7=IFCSIUNIT(*, .ENERGYUNIT., $, .JOULE.);
#8=IFCSIUNIT(*, .MASSUNIT., .KILO., .GRAM.);
#9=IFCSIUNIT(*, .THERMODYNAMICTEMPERATUREUNIT., $, .KELVIN.);
#10=IFCDERIVEDUNIT((#11, #12, #13), .SPECIFICHEATCAPACITYUNIT., $);
#11=IFCDERIVEDUNITELEMENT(#7, 1);
#12=IFCDERIVEDUNITELEMENT(#8, -1);
#13=IFCDERIVEDUNITELEMENT(#9, -1);
IFCSIUNIT
具体语义：
-
IfcSIUnit
- -Dimensions: IfcDimensionalExponents
- -UnitType: IfcUnitEnum
- -Prefix : IfcSIPrefix
- -Name : IfcSIUnitName
IfcDimensionalExponents例子说明
A velocity of 2 millimetres per second has a length exponent of 1 and a time exponent of -1. The remaining exponents are equal to 0.
速度为2mm/s的语义：IfcDimensionalExponents(1,0,-1,0,0,0,0)
IfcSIUnit
Dimensions: IfcDimensionalExponents
UnitType: IfcUnitEnum
Prefix : IfcSIPrefix
Name : IfcSIUnitName
IfcDimensionalExponents
LengthExponent: INTEGER
MassExponent: INTEGER
TimeExponent: INTEGER
ElectricCurrentExponent: INTEGER
ThermodynamicTemperatureExponent: INTEGER
AmountOfSubstanceExponent: INTEGER
LuminousIntensityExponent: INTEGER
«enumeration»
IfcUnitEnum
ABSORBEDDOSEUNIT
AMOUNTOFSUBSTANCEUNIT
AREAUNIT
DOSEEQUIVALENTUNIT
ELECTRICCAPACITANCEUNIT
ELECTRICCHARGEUNIT
ELECTRICCONDUCTANCEUNIT
ELECTRICCURRENTUNIT
ELECTRICRESISTANCEUNIT
ELECTRICVOLTAGEUNIT
ENERGYUNIT
FORCEUNIT
FREQUENCYUNIT
ILLUMINANCEUNIT
INDUCTANCEUNIT
LENGTHUNIT
LUMINOUSFLUXUNIT
LUMINOUSINTENSITYUNIT
MAGNETICFLUXDENSITYUNIT
MAGNETICFLUXUNIT
MASSUNIT
PLANEANGLEUNIT
POWERUNIT
PRESSUREUNIT
RADIOACTIVITYUNIT
SOLIDANGLEUNIT
THERMODYNAMICTEMPERATUREUNIT
TIMEUNIT
VOLUMEUNIT
USERDEFINED
«enumeration»
IfcSIUnitName
AMPERE // Unit for electric current.
BECQUEREL // Unit for radioactivity.
CANDELA // Unit for luminousintensity.
COULOMB // Unit for electric charge.
CUBIC_METRE // Unit for volume.
DEGREE_CELSIUS // Unit for thermodynamic temperature.
FARAD // Unit for electric capacitance.
GRAM // Unit for mass.
GRAY // Unit for absorbed radioactive dose.
HENRY // Unit for inductance.
HERTZ // Unit for frequency.
JOULE // Unit for energy.
KELVIN // Unit for thermodynamic temperature.
LUMEN // Unit for luminous flux.
LUX // Unit for illuminance.
METRE // Unit for length.
MOLE // Unit for amount of substance.
NEWTON // Unit for force.
OHM // Unit for electric resistance.
PASCAL // Unit for pressure.
RADIAN // Unit for plane angle.
SECOND // Unit for time.
SIEMENS // Unit for electric conductance.
SIEVERT // Unit for radioactive dose equivalent.
SQUARE_METRE // Unit for area.
STERADIAN // Unit for solid angle.
TESLA // Unit for magnetic flux density.
VOLT // Unit for electric voltage.
WATT // Unit for power.
WEBER // Unit for magnetic flux.
«enumeration»
IfcSIPrefix
EXA // 10^18.
PETA // 10^15.
TERA // 10^12.
GIGA // 10^9.
MEGA // 10^6.
KILO // 10^3.
HECTO // 10^2.
DECA // 10.
DECI // 10^-1.
CENTI // 10^-2.
MILLI // 10^-6.
MICRO // 10^-6.
NANO // 10^-9.
PICO // 10^-12.
FEMTO // 10^-15.
ATTO // 10^-18.
IFCCONVERSIONBASEDUNIT
具体语义
-
IfcConversionBasedUnit
- -Dimensions: IfcDimensionalExponents
- -UnitType: IfcUnitEnum
- -Name: IfcLabel Enum //The word, or group of words, by which the conversion based unit is referred to. X
- -ConversionFactor: IfcMeasureWithUnit
IfcMeasureWithUnit:
- For representing measure value together with its unit on the entity type attribute level; thus overriding the IFC model global unit assignments.
- For conversion based unit to give the conversion rate and its base.
具体语义：
-
IfcMeasureWithUnit
- -ValueComponent ： IfcValue
- -UnitComponent ：IfcUnit
IfcConversionBasedUnit
Dimensions: IfcDimensionalExponents
UnitType: IfcUnitEnum
Name: IfcLabel Enum
ConversionFactor: IfcMeasureWithUnit
IfcDimensionalExponents
LengthExponent: INTEGER
MassExponent: INTEGER
TimeExponent: INTEGER
ElectricCurrentExponent: INTEGER
ThermodynamicTemperatureExponent: INTEGER
AmountOfSubstanceExponent: INTEGER
LuminousIntensityExponent: INTEGER
«enumeration»
IfcUnitEnum
ABSORBEDDOSEUNIT
AMOUNTOFSUBSTANCEUNIT
AREAUNIT
DOSEEQUIVALENTUNIT
ELECTRICCAPACITANCEUNIT
ELECTRICCHARGEUNIT
ELECTRICCONDUCTANCEUNIT
ELECTRICCURRENTUNIT
ELECTRICRESISTANCEUNIT
ELECTRICVOLTAGEUNIT
ENERGYUNIT
FORCEUNIT
FREQUENCYUNIT
ILLUMINANCEUNIT
INDUCTANCEUNIT
LENGTHUNIT
LUMINOUSFLUXUNIT
LUMINOUSINTENSITYUNIT
MAGNETICFLUXDENSITYUNIT
MAGNETICFLUXUNIT
MASSUNIT
PLANEANGLEUNIT
POWERUNIT
PRESSUREUNIT
RADIOACTIVITYUNIT
SOLIDANGLEUNIT
THERMODYNAMICTEMPERATUREUNIT
TIMEUNIT
VOLUMEUNIT
USERDEFINED
«enumeration»
IfcLabelEnum
'inch' // Length measure equal to 25.4 mm
'foot' // Length measure equal to 304.8 mm
'yard' // Length measure equal to 914 mm
'mile' // Length measure equal to 1609 m
'square inch' // Area measure equal to 0.0006452 square meters
'square foot' // Area measure equal to 0.09290 square meters
'square yard' // Area measure equal to 0.83612736 square meters
'acre' // Area measure equal to 4046.86 square meters
'square mile' // Area measure equal to 2 588 881 square meters
'cubic inch' // Volume measure equal to 0.00001639 cubic meters
'cubic foot' // Volume measure equal to 0.02832 cubic meters
'cubic yard' // Volume measure equal to 0.7636 cubic meters
'litre' // Volume measure equal to 0.001 cubic meters
'fluid ounce UK' // Volume measure equal to 0.0000284130625 cubic meters
'fluid ounce US' // Volume measure equal to 0.00002957353 cubic meters
'pint UK' // Volume measure equal to 0.000568 cubic meters
'pint US' // Volume measure equal to 0.000473 cubic meters
'gallon UK' // Volume measure equal to 0.004546 cubic meters
'gallon US' // Volume measure equal to 0.003785 cubic meters
'degree' // Angle measure equal to π/180 rad
'ounce' // Mass measure equal to 28.35 g
'pound' // Mass measure equal to 0.454 kg
'ton UK' // Mass measure equal to 1016.0469088 kg, also known as long ton, gross ton, shipper's ton
'ton US' // Mass measure equal to 907.18474 kg, also known as short ton, net ton
'lbf' // Force measure equal to 4.4482216153 N, pound-force
'kip' // Force measure equal to 4448.2216153 N, kilopound-force
'psi' // Pressure measure equal to 6894.7572932 Pa, pound-force per square inch
'ksi' // Pressure measure equal to 6894757.2932 Pa, kilopound-force per square inch
'minute' // Time measure equal to 60 s
'hour' // Time measure equal to 3600 s
'day' // Time measure equal to 86400 s
'btu' // Energy measure equal to 1055.056 J, British Thermal Unit
IfcMeasureWithUnit
IfcConversionBasedUnitWithOffset
具体语义
-
IfcConversionBasedUnitWithOffset ： public IfcConversionBasedUnit
- -Dimensions: IfcDimensionalExponents
- -UnitType: IfcUnitEnum
- -Name: IfcLabel Enum //The word, or group of words, by which the conversion based unit is referred to. X
- -ConversionFactor: IfcMeasureWithUnit
- -ConversionOffset : IfcReal
IfcConversionBasedUnitWithOffset
IfcConversionBasedUnitWithOffset is a unit which is converted from another unit by applying a conversion factor and an offset.
IfcConversionBasedUnit
IfcConversionBasedUnitWithOffset
ConversionOffset : IfcReal
IfcDerivedUnit
具体语义
-
IfcDerivedUnit
- -Elements : IfcDerivedUnitElement //S[1:?] The group of units and their exponents that define the derived unit. X
- -UnitType : IfcDerivedUnitEnum //Name of the derived unit chosen from an enumeration of derived unit types for use in IFC models. X
- -UserDefinedType : IfcLabel IfcDerivedUnitElement
- -Unit : IfcNamedUnit //The fixed quantity which is used as the mathematical factor.
- -Exponent : INTEGER //The power that is applied to the unit attribute.
IfcDerivedUnitElement 例子
Newtons per square millimetre is a derived unit. It has two elements, Newton whose exponent has a value of 1 and millimetre whose exponent is -2.
IfcDerivedUnit
Elements : IfcDerivedUnitElement //S[1:?] The group of units and their exponents that define the derived unit. X
UnitType : IfcDerivedUnitEnum //Name of the derived unit chosen from an enumeration of derived unit types for use in IFC models. X
UserDefinedType : IfcLabel
IfcDerivedUnitElement
Unit : IfcNamedUnit // The fixed quantity which is used as the mathematical factor. X
Exponent : INTEGER
«enumeration»
IfcDerivedUnitEnum
ANGULARVELOCITYUNIT
AREADENSITYUNIT
COMPOUNDPLANEANGLEUNIT
DYNAMICVISCOSITYUNIT
HEATFLUXDENSITYUNIT
INTEGERCOUNTRATEUNIT
ISOTHERMALMOISTURECAPACITYUNIT
KINEMATICVISCOSITYUNIT
LINEARVELOCITYUNIT
MASSDENSITYUNIT
MASSFLOWRATEUNIT
MOISTUREDIFFUSIVITYUNIT
MOLECULARWEIGHTUNIT
SPECIFICHEATCAPACITYUNIT
THERMALADMITTANCEUNIT
THERMALCONDUCTANCEUNIT
THERMALRESISTANCEUNIT
THERMALTRANSMITTANCEUNIT
VAPORPERMEABILITYUNIT
VOLUMETRICFLOWRATEUNIT
ROTATIONALFREQUENCYUNIT
TORQUEUNIT
MOMENTOFINERTIAUNIT
LINEARMOMENTUNIT
LINEARFORCEUNIT
PLANARFORCEUNIT
MODULUSOFELASTICITYUNIT
SHEARMODULUSUNIT
LINEARSTIFFNESSUNIT
ROTATIONALSTIFFNESSUNIT
MODULUSOFSUBGRADEREACTIONUNIT
ACCELERATIONUNIT
CURVATUREUNIT
HEATINGVALUEUNIT
IONCONCENTRATIONUNIT
LUMINOUSINTENSITYDISTRIBUTIONUNIT
MASSPERLENGTHUNIT
MODULUSOFLINEARSUBGRADEREACTIONUNIT
MODULUSOFROTATIONALSUBGRADEREACTIONUNIT
PHUNIT
ROTATIONALMASSUNIT
SECTIONAREAINTEGRALUNIT
SECTIONMODULUSUNIT
SOUNDPOWERLEVELUNIT
SOUNDPOWERUNIT
SOUNDPRESSURELEVELUNIT
SOUNDPRESSUREUNIT
TEMPERATUREGRADIENTUNIT
TEMPERATURERATEOFCHANGEUNIT
THERMALEXPANSIONCOEFFICIENTUNIT
WARPINGCONSTANTUNIT
WARPINGMOMENTUNIT
USERDEFINED
IfcLabel