1. A method of measuring the dimensions of a surface comprising the steps of directing a light beam generally towards the surface from a range measuring means, located at a reference position, for measuring dimensions of the surface, reflecting the light beam away from the surface and towards a point in space which represents the virtual location of a point on the surface, retroreflecting the light beam in the opposite direction and in a substantially parallel manner, reflecting the light beam generally away from the surface to the range measuring means, and periodically moving the point in space relative to the surface and determining the location of the point in space from the reference position using the reflected light beam and the range measuring means.