3D digital reassembling of archaeological ceramic pottery fragments based on their thickness profile

📝 Abstract

The reassembly of a broken archaeological ceramic pottery is an open and complex problem, which remains a scientific process of extreme interest for the archaeological community. Usually, the solutions suggested by various research groups and universities depend on various aspects such as the matching process of the broken surfaces, the outline of sherds or their colors and geometric characteris-tics, their axis of symmetry, the corners of their contour, the theme portrayed on the surface, the concentric circular rills that are left during the base construction in the inner pottery side by the fingers of the potter artist etc. In this work the reassembly process is based on a different and more secure idea, since it is based on the thick-ness profile, which is appropriately identified in every fragment. Specifically, our approach is based on information encapsulated in the inner part of the sherd (i.e. thickness), which is not -or at least not heavily- affected by the presence of harsh environmental conditions, but is safely kept within the sherd itself. Our method is verified in various use case experiments, using cutting edge technologies such as 3D representations and precise measurements on surfaces from the acquired 3D models.

💡 Analysis

The reassembly of a broken archaeological ceramic pottery is an open and complex problem, which remains a scientific process of extreme interest for the archaeological community. Usually, the solutions suggested by various research groups and universities depend on various aspects such as the matching process of the broken surfaces, the outline of sherds or their colors and geometric characteris-tics, their axis of symmetry, the corners of their contour, the theme portrayed on the surface, the concentric circular rills that are left during the base construction in the inner pottery side by the fingers of the potter artist etc. In this work the reassembly process is based on a different and more secure idea, since it is based on the thick-ness profile, which is appropriately identified in every fragment. Specifically, our approach is based on information encapsulated in the inner part of the sherd (i.e. thickness), which is not -or at least not heavily- affected by the presence of harsh environmental conditions, but is safely kept within the sherd itself. Our method is verified in various use case experiments, using cutting edge technologies such as 3D representations and precise measurements on surfaces from the acquired 3D models.

📄 Content

3D digital reassembling of archaeological ceramic pottery fragments based on their thickness profile Michail I.Stamatopoulos†† and Christos-Nikolaos Anagnostopoulos†

†Social Sciences School, Cultural Technology and Communication Dpt. University of the Aegean, Greece, Email: canag@aegean.gr ††School of Science and Technology, Computer Science Dpt. Hellenic Open University, Greece, Email: std069191@ac.eap.gr Abstract: The reassembly of a broken archaeological ceramic pottery is an open and complex problem, which remains a scientific process of extreme interest for the archaeological community. Usually, the solutions suggested by various research groups and universities depend on various aspects such as the matching process of the broken surfaces, the outline of sherds or their colors and geometric characteris- tics, their axis of symmetry, the corners of their contour, the theme portrayed on the surface, the concentric circular rills that are left during the base construction in the inner pottery side by the fingers of the potter artist etc. In this work the reassembly process is based on a different and more secure idea, since it is based on the thick- ness profile, which is appropriately identified in every fragment. Specifically, our approach is based on information encapsulated in the inner part of the sherd (i.e. thickness), which is not -or at least not heavily- affected by the presence of harsh environmental conditions, but is safely kept within the sherd itself. Our method is verified in various use case experiments, using cutting edge technologies such as 3D representations and precise measurements on surfaces from the acquired 3D models.
Keywords: Thickness profile, sherds, 3D models, digital reassembling.

1. Introduction In every archaeological excavation, a variety of small ceramic pottery fragments (or called sherds) are revealed, which will provide valuable data for the excavation it- self. The nature of these small objects give them properties which make them highly resistant to time and wear. Moreover, sherds and these small fragments cannot be do not stolen, but and they remain near to the place where the ceramic vase is de- stroyed. Therefore the information carried within remain undeletable over the cen- turies, yet difficult to reassembled. The amount and the high value of information that is encapsulated within, rightly gives to the sherds, the title of best data carrier from ancient times to our days. For the reassembly of a ceramic vase vessel, the majority of the scientific methods suggested by various research groups and universities, depend on the outline of 2 Michail I. Stamatopoulos and Christos-Nikolaos Anagnostopoulos
   sherds, or matching the broken surfaces, the colours, geometric characteristics, the axis of symmetry, the corners of the contour, or even on the theme portrayed on it [1-8]. All these techniques suffer from the problems introduced by the external wear and decay of the material during the exposure in the soil. As a result, many charac- teristics on the surface of the sherd will be altered during the long time, leading to severe decrease in the efficiency of research methods based on external character- istics [8-10]. Therefore, it is no surprise that, to our knowledge and after extensive search in museum laboratories in countries with high archaeological interest (Greece, Italy, Vatican, Egypt), an automatic method that works effectively to re- store a true ancient theme is not available. In contrast, the process is performed manually by experts in the field, aligning the fragments by minimizing the distance between their adjoining regions while simultaneously trying to ensure geometric continuity across them (if possible).

2. The Thickness Profile (TP) method The proposed methodology is based on a new approach that can be considered sci- entifically more effective than others, as we seek important information encapsu- lated inside the core of the sherd and not in its surface. Our approach works even if some of the sherds are missing, it is not affected by the presence of external wear and damages, nor by the geometrical shapes or by the colour degradation of the pottery. The new method is based on exploration, extraction and utilization of all possible thickness information (i.e. Thickness Profile) which may have encapsulated inside each sherd. All this information, as a sequence of numbers, can be sorted, compared and provide a complete and efficient solution for the complex problem of recon- struction, reassembling, restoration and recovery of an ancient broken ceramic pot- tery which is fragmented into pieces, of random sizes and shapes. The basic idea is based on the fact that as the artist rotates the pliable clay on the wheel to create the pottery, it creates distinguishing thickness measurements, which are unaltered and can easily be detected. The gradual construction of a pottery on a

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