Units in a measurement session are fundamental to accuracy. It is important that a user understands the difference between the drawing units, property units and measurement or display units.
· Drawing Units: The drawing originator will be thinking in a given unit of measurement and the drawing units will reflect this. Everything created in the drawing will be full size, be it in millimetres, metres or feet and inches. The vital point is consistency throughout the model.
· Property Units: Once created, objects in a model can be selected and interrogated for their properties. It may be sensible to define a length of wall in millimetres but more useful to see its length property displayed in metres in the properties dialog box. The property units are useful in this regard.
· Measurement or Display Units: Irrespective of the above settings and choices made, output for measurement in CADMeasure BIM is controlled by the display units (also known as measurement units).
For example, areas defined in a model using millimetres as it's drawing units would give unsuitably large values if they were to be measured in square millimetres, so the display units can be set to square metres for a more sensible output.