Christos Doumas

A system for high-volume acquisition and matching of fresco fragments: reassembling Theran wall paintings

Although mature technologies exist for acquiring images, geometry, and normals of small objects, they remain cumbersome and time-consuming for non-experts to employ on a large scale. In an archaeological setting, a practical acquisition system for routine use on every artifact and fragment would open new possibilities for archiving, analysis, and dissemination. We present an inexpensive system for acquiring all three types of information, and associated metadata, for small objects such as fragments of wall paintings. The acquisition system requires minimal supervision, so that a single, non-expert user can scan at least 10 fragments per hour. To achieve this performance, we introduce new algorithms to robustly and automatically align range scans, register 2-D scans to 3-D geometry, and compute normals from 2-D scans. As an illustrative application, we present a novel 3-D matching algorithm that efficiently searches for matching fragments using the scanned geometry.

Contour-shape based reconstruction of fragmented, 1600 BC wall paintings

A novel general methodology is introduced for the computer-aided reconstruction of the magnificent wall paintings of the Greek island Thera (Santorini), which were painted in the middle of the second millennium BC. These wall paintings have been excavated in fragments, and as a result, their reconstruction is a painstaking and a time-consuming process. Therefore, in order to facilitate and expedite this process, a proper system has been developed based on the introduced methodology. According to this methodology, each fragment is photographed, its picture is introduced to the computer, its contour is obtained, and, subsequently, all of the fragments contours are compared in a manner proposed herein. Both the system and the methodology presented here extract the maximum possible information from the contour shape of fragments of an arbitrary initially unbroken plane object to point out possible fragment matching. This methodology has been applied to two excavated fragmented wall paintings consisting of 262 fragments with full success, but most important, it has been used to reconstruct, for the first time, unpublished parts of wall paintings from a set of 936 fragments.

Natural insecticides and insect repellents in antiquity: A review of the evidence

Archaeoentomological and palaeobotanical research at the Late Bronze Age site of Akrotiri on the Greek island of Santorini has suggested that natural insecticides and insect repellents were used in the storerooms of the site. A wide range of methods such as airtight storage, use of plant and animal substances, oils, minerals and ash were employed to control insect pests and reduce storage losses. Archaeological evidence from other sites as well as relevant information given by the documentary sources and the ethnographic record is reviewed.

Identification of geometrical shapes in paintings and its application to demonstrate the foundations of geometry in 1650 B.C

In this paper, an original general methodology is introduced to establish whether a handmade shape corresponds to a given geometrical prototype. Using this methodology, one can decide if an artist had the intention of drawing a specific mathematical prototype or not. This analysis is applied to the 1650 B.C. wall paintings from the prehistoric settlement on Thera, and inferences of great archaeological and historical importance are made. In particular, strong evidence is obtained suggesting that the spirals depicted on the wall paintings correspond to linear (Archimedes) spirals, certain shapes correspond to canonical 48-gon and 32-gon, while other shapes correspond to parts of ellipses. It seems that the presented wall paintings constitute the earliest archaeological findings on which these geometrical patterns appear with such remarkable accuracy.

Analyzing fracture patterns in theran wall paintings

In this paper, we analyze the fracture patterns observed in wall paintings excavated from Akrotiri, a Bronze Age Aegean city destroyed by earthquakes preceding a volcanic eruption on Thera (modern Santorini) around 1630 BC. We use interactive programs to trace detailed fragment boundaries in images of manually reconstructed wall paintings. Then, we use geometric analysis algorithms to study the shapes and contacts of those fragment boundaries, producing statistical distributions of lengths, angles, areas, and adjacencies found in assembled paintings. The result is a statistical model that suggests a hierarchical fracture pattern, where fragments break into two pieces recursively along cracks nearly orthogonal to previous ones. This model could be useful for predicting fracture patterns of other wall paintings and/or for guiding future computer-assisted reconstruction algorithms.

Ancient pests: the season of the Santorini Minoan volcanic eruption and a date from insect chitin.

Attributing a season and a date to the volcanic eruption of Santorini in the Aegean has become possible by using preserved remains of the bean weevil, Bruchus rufipes, pests of pulses, from the storage jars of the West House, in the Bronze Age settlement at Akrotiri. We have applied an improved pre-treatment methodology for dating the charred insects, and this provides a date of 1744–1538 BC. This date is within the range of others obtained from pulses from the same context and confirms the utility of chitin as a dating material. Based on the nature of the insect material and the life cycle of the species involved, we argue for a summer eruption, which took place after harvest, shortly after this material was transported into the West House storeroom.

Managing the Archaeological Heritage: The Case of Akrotiri, Thera (Santorini)

Abstract This article deals with the archaeological site of Akrotiri on the Cycladic island of Thera (Santorini), Greece, and demonstrates, in particular, how the construction of a new protective shelter has provided an opportunity for enhancing the present and future conservation and management of the site in accordance with, among other values, the aspirations of the local community. Drawing on the experience of the author as Director of the excavation, special emphasis will be placed on the features of the new bioclimatic shelter that can accommodate the continuous use of the site as both a scientific workshop and a tourist attraction.

Analyzing and simulating fracture patterns of theran wall paintings

In this article, we analyze the fracture patterns observed in wall paintings excavated at Akrotiri, a Bronze Age Aegean settlement destroyed by a volcano on the Greek island of Thera around 1630 BC. We use interactive programs to trace detailed fragment boundaries in images of manually reconstructed wall paintings. Then, we use geometric analysis algorithms to study the shapes and contacts of those fragment boundaries, producing statistical distributions of lengths, angles, areas, and adjacencies found in assembled paintings. The result is a statistical model that suggests a hierarchical fracture pattern where fragments break into two pieces recursively along cracks nearly orthogonal to previous ones. This model is tested by comparing it with simulation results of a hierarchical fracture process. The model could be useful for predicting fracture patterns of other wall paintings and/or for guiding future computer-assisted reconstruction algorithms.

Excavation and Rescue Operations: What to Preserve and Why

The major economic outlay that goes into the excavation, conservation and presentation of an archaeological site justifies the question, ‘Why should a society underwrite this expenditure and what should it expect in return?’ In other words, as Christos Doumas points out, the philosophy of site preservation should be clearly defined and understood so that public policy aims at both safeguarding of cultural heritage and protecting society from pointless effort and expense. The author is a professor in the Department of History and Archaeology at the University of Athens.

Near Surface Geophysical Archaeological Prospection at the Prehistoric Site of Akrotiri on Santorini/Thera

In February 2014 high-resolution ground penetrating radar and earth resistance tomography measurements have for the first time been used successfully for the distinct mapping of buried archaeological structures in the vicinity of the Bronze Age archaeological site of Akrotiri on Santorini/Thera in Greece.