Method and apparatus for calibration of 3-dimensional mapping systems applicable to automotive crash repair and diagnostics in which a calibration assembly provides accurate 3-dimensional optical inputs to a camera unit for calibration of the internal dimensional constants of the unit. The 3-dimensional calibration apparatus employs twin spaced mounting planes for patterns of optical emitters at known spacings and dispositions from the fixed camera unit position whereby tight tolerances in manufacture and assembly enable the apparatus to be more compact than a typical work piece to be mapped.