A method for measuring dimensions between selected points on a side of interest in objects selected for measurement by an optical measuring system comprising a flatbed scanner and a connected computer system through acquiring a reference image to provide corresponding image distance errors; and also acquiring a measurement object image. Deviation curves are provided as the basis for determining deviation errors in the measurement object image. Corrected measurement object image distances are formed through combining the deviation errors in the measurement object image distances with the corresponding measurement object image. These corrected measurement object image distances are used to determine distances between chosen pairs of those selected locations.