Application of multi-modal 2D and 3D imaging and analytical techniques to document and examine coins on the example of two Roman silver denarii

Abstract

This case study is applying imaging and analytical techniques from multiple scientific disciplines to digitise coins and evaluate 3D multi-modal visualisation. Two ancient Roman silver denarii were selected as test objects to establish whether the proposed digital recording methods can support professional numismatic comparison of features and properties. The coins raise questions concerning their provenance, authenticity, design, purpose of issue and historic usage, but they also pose considerable recording challenges due to their material and surface properties, which are the main focus in this paper. The coins have been examined by the following techniques: dome photography for image sets for PTM/RTI visualisation and photometric stereo; X-ray microtomography for detection of cracks or impurities; Scanning Electron Microscopy for detailed surface investigation; Energy-Dispersive X-ray Spectroscopy for elemental analysis; micro X-ray fluorescence spectrometry mapping; 3D laser and structured light scanning for 3D spatial capture; photogrammetry/structure from motion, focus-stacking. The results indicate the feasibility of such techniques for museum documentation and as contribution to scientific examination of coins in general.

Graphic Representation of The Degree of Historical-Archaeological Evidence: The 3D Reconstruction of The “Baker’s House”

“…establishes the principles and criteria to measure the quality levels of projects in this scope [6,20,21]. The studies conducted in the eld of virtual archaeology must include the scienti c approach, choose suitable technology, document the process and obtain an adequate visualisation [19,22,23].…”

Arduino-controlled Reflectance Transformation Imaging to the study of cultural heritage objects

“…Examples of RTI applications in the field of cultural heritage are diverse [11][12][13][14][15][16][17][18][19][20]. In general, small objects such as bone artefacts [13,15] or metallic objects (mostly coins) [12,17,[19][20][21] are the most characterized. With RTI it is possible to enhance the visibility of intentional modifications, tool marks, engraving details, etc.…”

Depth and Dimension: Exploring the Problems and Potential of Photogrammetric Models for Ancient Coins

“…Artefacts best suited for 3D modelling have structured surfaces and many edges, while unstructured and reflective artefacts can be problematic to capture. It is of little surprise, then, that ancient coins have not received the same attention as other classes of artefacts within the field of 3D modelling (Hess, Macdonald & Valach 2018;Macdonald, Moitinho & Hess 2017;Mara et al 2007). Ancient coins are small, with varied shapes and sizes, and are highly reflective, making them especially challenging to capture using photogrammetry.…”