Abstract: A method of making measurements on a body includes the steps of placing a body in a space which is divided along a plane into adjacent regions of contrasting illumination with the dividing plane intersecting the body, rotating the body relative to the dividing plane about an axis and sensing the position on the dividing plane of at least a part of the exterior surface of the body with a sensor sensitive to the illumination at a plurality of rotational positions of the body. The axis about which the body is rotated lies in the dividing plane and light sources which divide the space into adjacent regions of contrasting illumination are located on the dividing plane.