Developing Digital Survey Techniques for Archaeology
A Knowledge Transfer Project between the University of Nottingham and AOC Archaeology Group
Graeme Cavers MA PhD FSA Scot, KTP Associate, John Barber BA MA FSA (Lond.) FSA (Scot) MIFA, Company Partner, Jon Henderson MA D.Phil FSA (Scot.) MIFA, Academic Partner
The Trimble GS101 laser scanner (Plate 1)
AOC Archaeology Group and the University of Nottingham have entered into a research partnership concerned with the application of laser scanning and other high-precision survey techniques in archaeology. This two-year project aims to develop the ways in which new technologies like laser scanning can be most effectively adapted and put to use in the recording of standing buildings, archaeological field monuments and excavations (Plate 1).
Working in both the commercial and research sectors of archaeology, this project aims to develop standard operating procedures for high-precision survey techniques and to explore the range of applications of survey technology to archaeological recording.
The Project: a non-technical summary
Three dimensional model of
Rosslyn Chapel (Plate 2)
Working with AOC Archaeology's Trimble GS101 laser scanner, we have developed methodologies for recording standing structures, providing a rapid and highly accurate means of producing detailed elevations drawings and three-dimensional models of historic buildings (Plates 2 and 3).
By integrating data collected using more traditional survey equipment, however, such as total stations and digital cameras, we have been able to introduce 'interpreted' data into laser scan point clouds. This has been particularly useful in recording excavations, since although laser scanning is a highly effective method of obtaining large quantities of detailed data, it is difficult to incorporate archaeological interpretation into scanned surveys in the field.
Detailed elevations of Rosslyn Chapel produced
from laser scanner data (Plate 3)
In 2006, in conjunction with the River of Stone Project in Caithness, an excavation of a broch was recorded using laser scanning and on-site GIS complimentarily to traditional hand-drawn and written records with the aim of developing 3D survey techniques in archaeological field recording. This project is described further below.
Keiss foreshore landscape, Caithness (plate 4)
Another direction of the KTP research project has been in developing laser scanning as means of creating digital terrain models. The project has focused on producing raster and TIN digital terrain models compatible with standard desktop GIS georeferenced to ordnance survey coordinates. This technique was used to record the archaeological landscape at Keiss, Caithness, resulting in a terrain model of the foreshore area and three 'broch village' complexes (Plate 4).
Digital Survey Techniques: Developing the Profession
One of the principal aims of this project is to develop professional standards in high-precision archaeological recording, with the findings of this research feeding into standard operating procedures of AOC's field survey and historic building recording teams. We have also incorporated the research and recommendations of existing heritage survey special interest groups into our standard methodologies, and it is a further aim of the project to liaise closely with client users, regional archaeological data curators and heritage agencies to tailor our data collection to the most effective end product. Ultimately, pushing techniques of digital recording in archaeology forward is the driving force behind this work.
Case Study: Digital Excavation Recording at Keiss, Caithness
During the excavation of Whitegate and Keiss Harbour brochs in Caithness in 2006, laser scanning was employed alongside traditional recording by hand as a means of documenting the deposits and built structures encountered (Plate 5). Scanning was carried out at every stage where a hand-drawn plan was deemed necessary, and the resulting point-clouds registered to a common Ordnance Survey georeferenced site grid. Each stage of the excavation could thereby be overlain on the previous scan, providing phased plans that showed the depths of removed material. By digitising the resulting point-clouds in CAD, two-dimensional plans were produced and registered in to the site survey in GIS. By recording the locations of all finds and samples retrieved during the excavation in the same georeferenced coordinate system a GIS project was compiled recording the locations of all of the significant archaeological material. The result of this pilot project is a step towards the total three-dimensional recording of archaeological excavations. Further development of the techniques and the integration with GIS is planned for future seasons of excavation.
Excavated deposits at Whitegate Broch recorded by laser scanning (Plate 5)
Case Study: Quantification of Reconstructed Prehistoric Buildings at Spittal
As part of the Early Architecture Project, a branch of the River of Stone Project, two dry-stone structures- a chambered cairn and a broch tower- were built in Spittal quarry. Laser scanning was used to record the structures in millimetre detail, to provide quantitative data on the volumes of stone used and to assess distortion in the buildings during their collapse (Plates 6 and 7). Using analytical software tools at the post-processing stage, comparative statistics on the structures were compiled and detailed stone-by-stone CAD drawings were produced.
Scan of the Broch reconstruction in Spittal quarry (Plate 6)
Scan of the chambered Cairn reconstruction in Spittal quarry (Plate 7)