3D Reconstruction as a Form of Interpretation: Example of Excavation of the Medieval Peťuša Castle (Central Slovakia)

The paper presents a case study from the research of the High Medieval Peťuša Castle (Zvolen District) in Central Slovakia. Its aim is to present documentation and analytical procedures based on the application of 3D techniques in archaeology. During the archaeological excavation of the Peťuša Castle, several methods were used to document the castle hill, archaeological contexts and artefacts. The aim of the paper is to reference the possibilities of 3D visualization, which serves not only as an interesting presentation of archaeological results to the general public, but also for the work of the archaeologists themselves. The primary goal is to use 3D technology in the analysis and subsequent interpretation in a way that is not common in archaeological procedures. These methods are applied in the interpretation of the architecture of the castle, walking ground level and the surrounding environment. The main contribution is the clarification of spatial relations, visualization of the examined structures, and the opening of polemics within the interpretation levels. IANSA 2020 ● XI/1 ● 73–87 Matej Styk, Noémi Beljak Pažinová: 3D Reconstruction as a Form of Interpretation: Example of Excavation of the Medieval Peťuša Castle (Central Slovakia) 74 terraces and the south side of the castle is ca. 40 metres (in shortest direct line). The location of the Peťuša Castle – on a ridge in a narrow valley above the flow of the Gran River with a good view over the southern part of the Pliešovská basin (and thus the northwest part of the historical Zvolen county) – leads us to the logical assumption that this castle served as a guard post with its main task to control the local roads and waterways. This assumption is supported by its location in the near vicinity of a medieval ford on the Gran River, called Szellősrév (Maliniak, 2009, pp.216–218), closely beyond the edge of the medieval Zvolen land area, whose citizens had been freed from paying tolls throughout the Kingdom of Hungary (Ragač, 1998, pp.13–14). The castle is also located near old pathways (and former stopping points) used as trade roads (represented by visible carriage marks) leading from the south (from Pliešovská basin) to the town of Zvolen (Pažinová, et al. 2013, p.160, pic. 4 and 8; Slamová, et al., 2014; 2016). From the crossroads of trade roads located 450 m away from Peťuša Castle, a possible access path leads to the southern terrace above the castle ditch, the path being identified with the use of datasets from a point cloud obtained from the scanning technology LiDAR (light detection and ranging; source: National Forest Centre Zvolen, average height 700 m). The main goal of the Peťuša Castle excavation is to uncover the process of its construction and the subsequent use of the area, including the functional division of interior space. Among the main research questions belong the finding of its functionality, the duration and usage of the castle, and its involvement in an historical context. This article aims to point out the possibilities of using 3D technology for the analysis and subsequent interpretation of the Peťuša Castle disposition. The main focus of attention is the castle complex itself and the surrounding contemporary environment. The intention is one of greater understanding, clarification of spatial relations and a visualization of the studied structures by means of 3D documentation, and the reconstruction of Figure 1. Peťuša Castle, Zvolen District, Slovakia. Castle location in the vicinity of Zvolen Town above the Gran (Hron) river. Source: LIDAR by National Forest Center Zvolen (2018). Figure 2. Peťuša Castle, Zvolen District, Slovakia. Castle Hill Profile (view from the east) and an aerial view of the castle courtyard. Photo by Jan Beljak. 0 400 m IANSA 2020 ● XI/1 ● 73–87 Matej Styk, Noémi Beljak Pažinová: 3D Reconstruction as a Form of Interpretation: Example of Excavation of the Medieval Peťuša Castle (Central Slovakia) 75 the original space and simulation of its individual stages of construction. In just the last 15 years, archaeology has seen a growth in 3D-technology usage (see Barceló, 2000, pp.9–36). To a large extent, usage of these procedures is linked to the documentation of the archaeological situations and findings at a level of higher quality (e.g. Forte, 2010, pp.9–14). The 3D results themselves, whether based on scanning or photogrammetry, are commonly used within interpretative procedures (e.g. Callieri, et al., 2011), or as an expansion of the documentation methods used. In addition, the analytical meaning of this 3D technology is gradually going forward, where the focus is on different forms of spatial measurements (e.g. Dellepiane, et al., 2013, pp.201– 210). An extension of these procedures is 3D visualization, not only involving the presentation of the results but also serving the purpose of the research itself, just as it is used in the analysis of visibility, light and composition (e.g. Forte, 2008; Gruber, 2015, pp.63–68; Paliou, 2014, pp.91–113). At the same time, it is being enhanced with exact geographical and qualitative attributes through GIS (e.g. Aspöck and Fera, 2015, pp.2–8; Garstki, et al., 2015, pp.23–30). One remaining challenge is the discernment of time changes and the better application of natural laws in 3D simulations. 3D space can allow for the better archaeological reconstruction of an assemblage of finds and highlight spatial relations, as well as time determinism, within a broad archaeological context. Figure 3. Peťuša Castle. Disposition of trenches in the castle hill with an elevation model. Green polygons show trenches which were 3D documented using Structure from Motion. Blue lines mark interpreted structures: A – keep, B – structure with stone fundament, C – water tank, D+E – first phase structures, F – second