Measuring base on the virtual datum

In some condition, the  user required perform the comparative measurement base on video measurment machie of the virtual datum. Take the following workpiece as an example, you must create the virtual datum in order to observe whether the 4 circles are symmetrical to the center lines of the rectangle.

Because they are virtual datums, so you need to establish the virtual datum by using the construction method, that is to create the workpiece coordinate system with the construction element. Then align the CAD drawing and the workpiece. The steps are as follows: