The height and/or deformation of a surface of an object (10) defined in terms of x, y and z coordinates is measured by projecting a divergent beam of light 21) onto the surface to produce a periodic pattern of fringes (30. A CCD camera (40) views the surface from another angle and images the reflected light. Phase information is extracted from at least one image to produce an optical print (36) of the object containing phase information and image-coordinates information both being related to camera pixel position, the image-coordinates being associated with phase information corresponding to the object coordinates. A processor (50) calculates the object-coordinates of the surface points through mathematical functions describing x, y and z. These mathematical functions take account of the spatial configuration and specifications of the system which are established by calibration procedures involving eg. measurements of a theodolite (60) .