The Measurement modal performs measurements based on the transformation matrix and Unit System information provided in the drawing. These values can be inspected with the About button.
Dynamic changes of the Unit System can be done through the command Calibrate
The measurement command supports a number of different measurement types:
The measurement command also supports snap modes:
Note: For snap-modes to work, the drawings must be converted using the conversion parameter hlall, see documentation for AutoCAD Handle-Based Processing, so in the conversion there is an associated handle for the object to snap to.
Also see Settings on how to dynamically add a parameter.