IfcConversionBasedUnit
實體定義
IfcConversionBasedUnit用於定義具有基本單位轉換率的單位。為了識別一些常用的基於轉換的單位，表4中列出了Name屬性的標準名稱（不區分大小寫）。
| Name | Description |
|---|---|
| '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 |
Standard unit names
一英寸是換算單位。它來自英制，名稱為“英寸”，可以透過25.4毫米的單位與國際單位制（毫米）相關。腳部也是一個轉換單元。它來自帝國系統，名稱為“英尺”，可以直接或透過名為“英寸”的單位與IfcSIUnit（毫米）相關。請注意，幾個美國習慣單位與同名的英制單位（非英制單位）不同。
注：定義依據ISO/CD 10303-41:1992
基於轉換的單位是基於具有單位的度量定義的單位。
注：實體適用於ISO 10303-41中定義的conversation_based_unit。
IFC1.5.1中的新實體。
IFC2x3 新增了典型單元的標準名稱。
IFC4 新增了更多名稱：平方英寸、平方英尺、平方英里、平方碼、立方英寸、立方英尺、立方碼、流體盎司英國/美國、噸英國/美國和度。
Attribute inheritance
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcNamedUnit | |||||
| 1 | Dimensions | IfcDimensionalExponents | [1:1] | The dimensional exponents of the SI base units by which the named unit is defined. | X |
| 2 | UnitType | IfcUnitEnum | [1:1] | The type of the unit. | X |
| IfcConversionBasedUnit | |||||
| 3 | Name | IfcLabel | [1:1] | The word, or group of words, by which the conversion based unit is referred to. | X |
| 4 | ConversionFactor | IfcMeasureWithUnit | [1:1] | The physical quantity from which the converted unit is derived. | X |
| HasExternalReference | IfcExternalReferenceRelationship @RelatedResourceObjects |
S[0:?] | Reference to external information, e.g. library, classification, or document information, which is associated with the conversion-based unit. | X | |
EXPRESS Specification
ENTITY IfcConversionBasedUnit
SUPERTYPE OF(IfcConversionBasedUnitWithOffset)
SUBTYPE OF (IfcNamedUnit);
Name : IfcLabel;
ConversionFactor : IfcMeasureWithUnit;
INVERSE
HasExternalReference : SET OF IfcExternalReferenceRelationship FOR RelatedResourceObjects;
END_ENTITY;
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