The getter returns either instance of some predefined measurement unit, associated with currently initialized AspectNumeratorX, AspectDenominatorX, AspectNumeratorY and AspectDenominatorY values, or instance of the ImGearARTMeasurementUnit with Name equal to "Custom" and Aspect values, initialized from corresponding Aspect values of the PolyRuler.
Note: The annotation must be added to the ImGearARTPage prior to using this property.
Note: If the AspectKind is ImGearARTAspectKind.Absolute, please initialize Resolution prior to using this property, otherwise ImageGear.Core.ImGearException will be thrown. The resolution is necessary for initialization of Aspect properties in Absolute mode.