Abstract: A method and apparatus for making precise measurements as small as in submicron distances of an object or specimen (13) includes a stage (18) which is movable under the control of a microprocessor (20). An instrument, such as a scanning electron microscope (10) scans the object (13) to obtain a first scan representation thereof. The stage (18) is then shifted a precise known distance and a second scan is made thereof. The results of the two scans are stored and compared by the microprocessor (20) to determine the apparent magnitude of the stage shift in arbitrary units. This apparent magnitude is then equated to the known precise shift distance to calibrate the arbitrary units. The microprocessor (20) can then calculate the desired measurement from the data of either of the two scans stored therein.