The method for measurement and visualisation, which was formerly used for industrial purposes, has now conquered the documentation at institutions which aim at the preservation of culture. At the Archaeological Heritage Office of Saxony, engineers and scientists have already been working with 3D scanning technologies since 2005.
The high-definition 3D digitalisation of objects using close-range scanners and the SfM (Structure from Motion) process based on digital photos is now used more and more frequently at institutions for the preservation of culture in order to document the collections. The precise measuring technology in combination with a high efficiency in staff and time management are only a few of the advantages. In addition, the different options for subsequent use of the 3D data and the scans’ reproducibility in diverse forms (photorealistic images, drawings, 3D models or printings) also guarantee a conservation of the original.
Since its scientific beginnings, archaeology has used drawn reconstructions and documentation of artefacts, fragments and features as means of communication on the research object. 3D technology offers possibilities which are much more than a simple substitution of photography and drawn illustrations. At the Archaeological Heritage Office in Saxony, various scanners and 3D modelling methods have been used since 2005 for the documentation of artefacts and their scientific analysis. The application possibilities are, for example, mass digitalisation of artefacts with simultaneous recording of relevant measurements and the automatic reconstruction of vessels, the analysis of typological sequences, manufacturing techniques and traces of processing just as well as monitoring of conserved waterlogged wood.
In the area of artefact documentation, two scanners are used: one laser scanner (Konica-Minolta VI-910) which works with triangulation technology and has a lateral resolution of max. 0.2 mm and a depth precision of 0.1 mm, the other one is a fringe projection scanner (Breuckmann smartSCAN 3D-HE), which can reach a resolution of up to 0.018 mm. In addition, a hand scanner (Artec EVA) is employed at excavations, for objects and archaeological structures which are bigger and more difficult to access. It has proved to be useful underground, for example, for the recording of mining traces in medieval mines. A terrestrial scanner (Riegl LMS-420i) is used to document difficult archaeological findings on-site. The Archaeological Heritage Office in Saxony was furthermore an application partner in a joint project of the Dresden University of Applied Sciences (HTW Dresden) and the Freie Universität Berlin. The aim of this project was to develop a remote-controlled quadrocopter for the documentation of geological findings and the calculation of surface models using the perspectively taken photographic series. Since 2014, the Archaeological Heritage Office has been using its own quadrocopter successfully.
Since the very beginning, the processing of the 3D data is specifically adapted to the needs of archaeology and the focus is on the comprehensive automation of work processes. In cooperation with the chair for Computer Graphics and Visualisation of the TU Chemnitz, the Archaeological Heritage Office in Saxony develops the documentation software TroveSketch. The software makes the automatised orientation of the scans of vessels and fragments and the measurement of hollow forms (size, significant measurements, volume) possible. All of the data which is relevant for the classification of the vessels are collected and saved with the scan. Besides the visual comparison of vessels by the researcher, a purely mathematical analysis of the data through very many scans of different vessels without much extra workload is now possible. The additional software module VesselReconstructor is able to reconstruct virtual vessels from the data collected during the scan of the sherds and thus assisting in the scientist’s shape analysis. In this process, the sherds positioned in the right place are completed to form a hollow form, making it possible to identify the original container form much better.
While the traditional artefact drawing depends on the illustrator’s knowledge, experience and accuracy, the 3D scan offers a very precise replica of the object’s surface. The software allows different lighting scenarios and stylisation degrees. Combined with the possibility to add or omit the colour values gathered during the scan, this provides the scientist with different illustration varieties, thus offering better insights for detailed questions, for example regarding manufacturing methods or processing traces, than photographic recording. The neutralisation of light-shadow-effects or highlights and the complete independence of the surface modelling from impairment due to dark textures take the measurability of tool marks to the next level. In the process, the protection of the object itself is also extremely important, since it is usually very delicate and threatened with decay due to its long time in the ground. 3D scans can also offer help in this area. Scanning is normally used for archaeological moist wood objects before and after their conservation. This enables a scientist to work with precise 3D models, even during the long-lasting conservation period when the object is inaccessible. At the same time, this enables restorers to evaluate possible shrinking processes during the conservation just as well as other changes in the woods using a monitoring process.
More than 10,000 findings have already been scanned in the Archaeological Heritage Office in Saxony. In the future, the focus will be put on the permanent saving of the data and the further development of application options for archaeological purposes.
Dr. Regina Smolnik
The author studied Pre- and Protohistory, Art History and European Ethnology. After receiving her doctorate, she became head of the Inventory Project of Archaeological Monuments at the Archaeological Heritage Office in Dresden, then went on to become head of the department Museum/Restoration in the Brandenburgisches Landesamt für Denkmalpflege und Archäologisches Landesmuseum. Since 2009, she has been State Archaeologist of the Free State of Saxony. She is Chair of the AG Sammlungsmanagement of the Documentation Working Group in the German Museums Association.