About Coordinate Systems
Reference coordinate systems are used in measuring points and verifying tolerances. Coordinate Measuring Machines have a set of memory locations that you can fill up with reference coordinate system definitions. In addition, a CMM has a notion of a current reference coordinate system, which is kept in a working buffer.
When defining a CMM operation, you have to specify the Machine Csys, which will be used as the initial 0,0,0 point for the DMIS program for this operation. You can later create additional reference coordinate systems by clicking > 
Reference Coordinate System. A Ref Csys can only be constructed, or transformed, relative to the Machine Csys, another Ref Csys, and measured and constructed entities.
Reference Coordinate System. A Ref Csys can only be constructed, or transformed, relative to the Machine Csys, another Ref Csys, and measured and constructed entities.Before additional reference coordinate systems are created, the Machine Csys is considered to be the current coordinate system, i.e., it will be automatically used as the output origin for measure steps, etc. When you create a new Ref Csys, it automatically becomes current.