3D Reconstruction

Paper presented at 'Middle and Late Helladic Laconia: Competing Principalities?', at the Netherlands Institute of Archaeology, 12-13 April 2019, Athens. Organised by the Netherlands Institute of Archaeology, the Ephorate of Antiquities of Laconia and the University of Groningen (https://www.aegeussociety.org/wp-content/uploads/2019/04/Laconia-Program-12-13-April-2019.pdf).

This study is concerned with the reconstruction of the architecture of a so-called Built Chamber Tomb found in the early Mycenaean cemetery of Ayios Vasilios, mainland Greece (approx. 1700-1420 BC). The Built Chamber Tomb is a rather rare tomb type that signals some of the first architectural elaborations on the mainland and they are testament to a change in funerary practices and beliefs. At the same time pervasive social changes take place with the appearance of social differentiation.
The first part of this study aims at understanding both how the tomb collapsed and how it was originally constructed, as well as the sequence of actions that have taken place inside the tomb. More than 25 people were buried inside at different times, which means the tomb was repeatedly opened with every single internment. To understand the construction and use of this tomb, we use a number of Digital Archaeology recording techniques, such as Structure from Motion (photogrammetry) and
Virtual Reality (in cooperation with the Reality Center at the University of Groningen).
In the second part of this paper particular attention will be paid to architectural parallels to obtain a better understanding regarding the development of mortuary architecture, both within Laconia and
the wider Aegean. The first results suggest that the builders were experimenting with the idea of using a corbelling method to support the superstructure of the tomb. Based on the resultant hypothesis, Tomb 21 could perhaps be equated with other locally and regionally known built tombs such as Psychiko and Palaiochori.

Paper presented at Visual Heritage 2018, CHNT23 (https://www.chnt.at/destruction-construction-and-reconstruction-the-built-chamber-tomb-of-the-north-cemetery-at-ayios-vasilios-lakonia/), 12-15 November 2018, Vienna (Austria). PhD/Master Session, chaired by Martina Polig.

This study is concerned with the reconstruction of the architecture of a so-called Built Chamber Tomb found in the early Mycenaean cemetery of Ayios Vasilios, mainland Greece (approx. 1700-1420 BC). The Built Chamber Tomb is a rather rare tomb type that signals some of the first architectural elaborations on the mainland and they are testament to a change in funerary practices and beliefs. At the same time pervasive social changes take place with the appearance of social differentiation.
The main topic is the reconstruction, construction, multiple use and destruction of a partially preserved tomb called Tomb 21. The architecture of this particular tomb – especially the roof – is uncertain. This is because this tomb was introduced in a process of experimentation: tomb 21 is both larger and more labour intensive than the surrounding tombs and built for multiple burials. This has major repercussions for the construction of the roof. At least 25 individuals have been buried inside Tomb 21 at different times, which means the tomb was repeatedly opened and closed with every single internment. The roof was clearly not a simple closing mechanism never to be touched again, it was the most dynamic part of the construction.
The goal of this study is to understand both how the tomb collapsed and how it was originally constructed. To do so, we use a number of digital techniques, such as photogrammetry and Virtual Reality. In cooperation with the Virtual Reality/Augmented Reality Center of the University of Groningen we create a digital environment in which it is possible to ‘puzzle’ back together the various pieces and create a number of scenarios and reconstructions. This allows us to gain a better understanding of the sequence of actions that have taken place inside the tomb. This project is also used to train students in the possibilities and application of photogrammetry, 3D modeling and VR techniques. The reconstructions themselves will be used for heritage purposes, in order to visualize the process of experimentation with new mortuary practices and to present the process of social differentiation to the public.

The 3D reconstruction of real-world heritage objects using either a laser scanner or 3D modelling software is typically expensive and requires a high level of expertise. Image-based 3D modelling software, on the other hand, offers a cheaper alternative, which can handle this task with relative ease. There also exists free and open source (FOSS) software, with the potential to deliver quality data for heritage documentation purposes. However, contemporary academic discourse seldom presents survey-based feature lists or a critical inspection of potential production pipelines, nor typically provides direction and guidance for non-experts who are interested in learning, developing and sharing 3D content on a restricted budget. To address the above issues, a set of FOSS were studied based on their offered features, workflow, 3D processing time and accuracy. Two datasets have been used to compare and evaluate the FOSS applications based on the point clouds they produced. The average deviation to ground truth data produced by a commercial software application (Metashape, formerly called PhotoScan) was used and measured with CloudCompare software. 3D reconstructions generated from FOSS produce promising results, with significant accuracy, and are easy to use. We believe this investigation will help non-expert users to understand the photogrammetry and select the most suitable software for producing image-based 3D models at low cost for visualisation and presentation purposes.