DRO = Digital Read Out. Attach a scale/sensor onto each axis, and you get a digital display of position. Zero that, and you have a digital display of displacement. Apply a *2 factor via button-press and you can directly read the influence of a cross-slide movement into the diameter of the workpiece, remove the scale factor and you read the influence on the radius of the workpiece. Store positions into memory for quick indexing around the workpiece. Displays in either imperial or metric.

Worth a consideration - you can get lash-ups with cheap digital callipers and similar if money is a consideration.