Proceedings of the CIPA WG 6 International Workshop on Scanning for Cultural Heritage Recording

Böhler, Wolfgang

Bibliographic data

Monograph

Persistent identifier:: 830281592

Title:: Proceedings of the CIPA WG 6 International Workshop on Scanning for Cultural Heritage Recording

Sub title:: September, 1 - 2, 2002, Corfu, Greece

Scope:: 159 Seiten

Year of publication:: 2002

Place of publication:: Thessaloniki

Publisher of the original:: Publ. ZITI

Identifier (digital):: 830281592

Illustration:: Illustrationen

Signature of the source:: T 15 B 1303

Language:: English

Additional Notes:: Literaturangaben

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Böhler, Wolfgang

Corporations:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Adapter:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Founder of work:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Other corporate:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2015

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: 6. VARIOUS SUBJECTS

Document type:: Monograph

Structure type:: Chapter

Section

Title:: [Inhaltsverzeichnis]

Document type:: Monograph

Structure type:: Section

- 136 - 2. OBJECT DESCRIPTION The two gold quiver or “Gorythes” belongs to what is known as “Amazones’s gold”, a choice of prestigious objects illustrating one crucial moment of wandering Eurasian steppes people’s history (southern of the Ural, Kazakhstan, China), renewing the traditional forms of Scythes art. All the exposed objects came from regional Rostov and ethnographic Azov Museum in Russia. 3. METHODOLOGY The digitalisation of these objects was carried out with the Minolta VI900 scanner. Combining digital photogrammetry and laser scanning allows to reach a high degree of efficiency. The high quality required for object documentation did not permit the unique use of digital photogrammetry and stereo matching. At that time, our measurements were carried out by digital photogrammetry, with restitution of digital surfaces models (DSM) and orthophotos at original scale. Time and infrastructures necessary to capture information and their edition was considerable and thus, did not allow to apply these techniques to secondary order objects. In fact, photogrammetry implies high value added work combined with strong matching algorithm for precise surface reconstruction. Even if there are systems that use feature extraction or image matching process, they are limited in precision for close-range surface editing. Figure 2: Digitalization was carried out by leaving the object while removing the principal protective glass. For that reason and combined with the constraints of not accessing the objects, it was decided to use a close range laser scanner able to reach sub- millimetre resolution. Then, a methodology of surface comparison was established for archeological and historical interpretation. The question was to determine wether or not these two gold quivers were hand-made or issued from a same mould. 3.1 Data acquisition: Digitalisation is made by leaving the object while removing the principal protective glass and then start the survey with the laser scanner. The acquisition process is not affecting the quiver since the laser beam is not of sufficient energy to alter the object surface. Several measurement are made form different viewing angles in order to cover all the quiver. Each part were measured by seventeen to twenty scans with 320.000 points each. Meanwhile the laser scanner acquisition, the system is able to take a picture stored as a textured photo, and then draped over the object for visualization purposes. These textures of high-resolution were acquired with a digital camera Sinar P, equipped with a numerical back PowerPhase FX which can reach up to 150 millions pixels by image. The reconstruction of this man made object is rather complex since its reduced dimension of nearly one meter, and also with the large amount of sculpted reliefs. Hence, It is necessary to use subsampling algorithms (reduce amounts of measurements) generated by these digitalizations and proceed to transformations on the regulated mathematical surfaces (TIN). This is done by filtering the scatter plot for removing noise and polluted measurements. Finally, we obtain a set of cloud points which need to be registrated. 3.2 Global registration: A second step is to reference all the scans to build a complete object. This task was done with the commercial software Polygon Edit Tool from Minolta delivered with the scanner. The latter proceed to registration with morphological rules to combine different scans and thus, construct the entire object. Indeed, the quivers were measured with an accuracy close to an half-millimetre. If needed, some control points may be acquired to help the registration process and to reference one model to another. We chose to study the quivers matrice by matrice since a global curvature difference was noticed. Thus the registration process was fine tuned locally. Photographic images digitised in high resolution are then applied to the geometrical model for realization of photorealists models or 1/1 scale orthophotos

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