Definition from ISO/CD 10303-41:1992: A plane angle measure is the value of an angle in a plane.
Usually measured in radian (rad, m/m = 1), but also grads may be used. The grad unit may be declared as a conversion based unit based on radian unit.
NOTE IfcPlaneAngleMeasure is used where angles need to be described to an accuracy of less than one degree and expressed as decimal parts of an angle. It is widely used for angular measurement except for situations where accuracy needs to be defined using arc measurement; for which purpose the IfcCompoundPlaneAngleMeasure is provided.Type: REAL
NOTE Corresponding STEP name: plane_nagle_measure, please refer to ISO/IS 10303-41:1994 for the final definition of the formal standard.
HISTORY New type in IFC Release 1.5.1.