In IFC you can define your own units. You can do this on the IfcProject level, but in certain cases you can also set units on a per-value basis. The BQL allows you to extract exactly what is in the IFC file, additionally BQL allows you to dictate in which units you would like to extract or select data. The BIM viewer will automatically convert all the available units.
Global unit settings
For convenience, you can set the default units in your BQL per unit type. This will have an effect on all returned values.
Length units in millimeters
GET attribute.OverallWidth USING LENGTH_UNIT=mm"OverallWidth": { "name": "OverallWidth", "value": 1000, "type": "double", "unit": "MILLI_METER", "original_unit": "METER", "original_value": 1 }Length units in meters
GET attribute.OverallWidth USING LENGTH_UNIT=m"OverallWidth": { "name": "OverallWidth", "value": 1, "type": "double", "unit": "METER" }Note how the example only request the “OverallWidth” attribute, but the units are applied to all returned values that have a LENGTH_UNIT (also properties, calculated values etc…)
Available units
Definition order | Unit type | Allowed values |
|---|---|---|
1 | LENGTH_UNIT | mm, cm, dm, m, km, in, ft, yd, mi |
2 | AREA_UNIT | mm2, cm2, dm2, m2, m2, km2, inch2, yard2, foot2, acre, mile2 |
3 | VOLUME_UNIT | mm3, cm3, dm3, m3, inch3, foot3, yard3, l |
4 | MASS_UNIT | mg, cg, g, kg |
5 | TEMPERATURE_UNIT | dc |
Note that the order of defining the default units has no effect on the outcome, but the syntax does require a specific order when defining them (this is inherent to the technology used to parse the queries). The required order is the same order as in the above table.
Also note that in BQL for the exponents we are using regular characters and not the superscript characters, to make it easier for developers to type them. In the query output superscript is used for the symbols, again to make life easier.
Unit type | Value | Symbol |
|---|---|---|
Length | MILLI_METER | mm |
Length | CENTI_METER | cm |
Length | DECI_METER | dm |
Length | METER | m |
Length | KILO_METER | km |
Length | INCH | in |
Length | FOOT | ft |
Length | YARD | yd |
Length | MILE | mi |
Area | SQUARED_MILLI_METER | mm² |
Area | SQUARED_CENTI_METER | cm² |
Area | SQUARED_DECI_METER | dm² |
Area | SQUARED_METER | m² |
Area | SQUARED_KILO_METER | km² |
Area | SQUARED_INCH | in² |
Area | SQUARED_FOOT | ft² |
Area | SQUARED_YARD | yd² |
Area | SQUARE_MILE | mi² |
Area | ACRE | ac |
Volume | CUBIC_MILLI_METER | mm³ |
Volume | CUBIC_CENTI_METER | cm³ |
Volume | CUBIC_DECI_METER | dm³ |
Volume | LITER | l |
Volume | CUBIC_METER | m³ |
Volume | CUBIC_INCH | in³ |
Volume | CUBIC_FOOT | ft³ |
Mass | GRAM | g |
Mass | MILLIGRAM | mg |
Mass | CENTIGRAM | cg |
Mass | KILOGRAM | kg |
Temperature | DC | °C |
Unitless | UNITLESS |
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