The invention is a method and apparatus for measuring the dimensions of a parcel for use in a parcel processing application of a data processing device, wherein a parcel is placed in a predetermined position on a weighing scale with a platform having at least two raised sides for placing the parcel thereagainst. When the parcel is placed, beams from a first laser source and from a second laser source are transmitted onto the parcel at a first and second target spot wherein the target spots are a known distance from each other, and wherein the target spots are in a line parallel to the weighing scale. The beams are reflected back to a rotating mirror assembly and to a beam detector. The mirror assembly is located in a line parallel to one of the two laser beam sources and is rotated at a constant rate so as to focus on the first and second target spots. The angle of focus of the mirror assembly is determinative of the distance from the mirror assembly to the parcel surface. If the determined angle of focus does not allow the mirror assembly to properly focus on the target spots, then the assembly is adjusted under control of the data processing device by adjusting the angle of focus wherein the degree of adjustment is determinative of a change in distance between the mirror assembly and the parcel surface.