Fig. 6

a Superposition of the thirteenth century bell profile measurements assessed through the 3D scanning technique (in green) and the profile obtained through the measurements with the optical displacement transducer and the slide gauge (in red). b Inner and outer surfaces of the bell at four different heights (scanner in green and optical displacement transducer and laser/gauge technique in red). c and d Colour representation of the distances in millimeters between the 3D geometries, assessed through the scanning technique and the profile obtained through the measurements with the optical displacement transducer and the slide gauge