The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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Articles | Volume XLII-2/W18
Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-2/W18, 85–89, 2019
https://doi.org/10.5194/isprs-archives-XLII-2-W18-85-2019
Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-2/W18, 85–89, 2019
https://doi.org/10.5194/isprs-archives-XLII-2-W18-85-2019

  29 Nov 2019

29 Nov 2019

3D MODELLING OF THE MAMARI TABLET FROM THE RONGORONGO CORPUS: ACQUISITION, PROCESSING ISSUES, AND OUTCOMES

L. Lastilla1,2, R. Ravanelli3, M. Valério3, and S. Ferrara3 L. Lastilla et al.
  • 1Department of Computer, Control and Management Engineering Antonio Ruberti (DIAG) – Sapienza University of Rome, Italy
  • 2Sapienza School for Advanced Studies, Rome, Italy
  • 3Department of Classical Philology and Italian Studies (FICLIT), Alma Mater Studiorum – University of Bologna, Italy

Keywords: 3D modelling, Laser scanning, Structured light, Precise 3D digitization, Rongorongo inscriptions

Abstract. Rongorongo is an undeciphered script inscribed on wooden objects from Easter Island (Rapa Nui) in the Pacific Ocean. The existing editions of the inscriptions, and their widespread locations in museums and archives all over the world today constitute a serious obstacle to any objective paleographical assessment. Thus, with a view to a potential decipherment, creating 3D models of the available corpus is of crucial importance, and one of the objectives of the ERC INSCRIBE project, based at the University of Bologna with Professor S. Ferrara as Principal Investigator. In this preliminary work, we present the results of the 3D digitization of the Mamari tablet, one of the longest inscriptions in Rongorongo, housed in the Museum Archives of the Congregazione dei Sacri Cuori di Ges`u e Maria in Rome. The tablet is made of wood, with a shiny reflecting surface, characterized by a mainly dark texture. The 3D modelling was carried out with the ScanRider 1.2 laser scanner manufactured by VGER, based on Structured Light technology, taking care to ensure the legibility of each sign while preserving the overall shape of the object as precisely as possible. To overcome the difficulties inherent in the object’s complex fabric, the Mamari tablet was acquired in separate sections (joined together during processing through specific markers), thus managing to optimize the optical parameters of the laser scanner, such as the exposure of the camera and the depth of field of the projector. Furthermore, an evaluation of the 3D reconstruction precision was also carried out, highlighting a precision of few hundredths of millimeters, in agreement with the claimed nominal standard deviation. In addition to the 3D model produced, one of the main results of this endeavor was the definition of a successful method to scan such complex objects, which will be replicated to finalize the complete 3D modelling of the whole Rongorongo corpus of inscriptions.