HIGH ACCURACY 3D DIGITISATION OF THE GOETHE ELEPHANT SKULL USING HAND-HELD 3D SCANNING SYSTEMS AND STRUCTURE FROM MOTION – A COMPARATIVE CASE STUDY

Abstract. The Goethe Elephant skull is a cultural object of great interest. For the highly accurate 3D digitisation of the object, a hand-held 3D scanning system (Creaform GO!Scan) and Structure-from-Motion (DSLR camera) were used. The aim is a complete spatial reconstruction with a resolution of 0.5 mm and an accuracy level of approximate 0.5 mm. The skull consists of three parts, which have very complex but also very simple surface structures. For both methods the data acquisition and processing is described in detail. In both cases, a complete textured meshed 3D model could be calculated without shadows due to the use of camera-fixed lighting. The 3D models fulfil the desired target resolution and accuracy, verified by independent reference lengths and by the manufacturer's specifications. In addition, the colour values of the texture were calibrated with the help of the ColorChecker Digital SG. A visual and geometric comparison of the two models shows that both methods are very well suited for high-precision 3D object reconstruction on a similar level of accuracy. Furthermore, the advantages and disadvantages of the methods are compared. The main advantage of the applied hand-held scanner is the real-time verification of the model during data acquisition. The established SfM convinces with its flexibility regarding resolution and camera positioning.