Getting the Measure of Brochs: Using Survey Records Old and New to Investigate Shetland’s Iron Age Archaeology

This paper addresses the advantages as well as the obstacles in practicing photogrammetry based on archival photos of archaeological sites and examines how the results can be put to use for further research, preservation, restoration and monitoring rates of deterioration. While the extensive use of historic aerial photographs has been applied to photogrammetric modeling, archaeological excavation archives have been largely ignored. Historically archaeological excavations have been vigorously documented photographically and many of these photographs are available in archives. Not all photo archives are suitable for photogrammetry as they were not photographed with the intention of overlap and other photogrammetric qualities. By selectively choosing photographs with common points and manipulating exposures, cropping and other properties to enhance commonality, 3D models of past structures and excavations can allow us to revisit them, produce accurate measurements and view angles that were never photographed. Some sites are still available for modern comparison and surveying, allowing us to quantitatively compare conditions at the time of excavation with the current state of those sites. Given the right treatment, retrospective photogrammetry will have impacts in the preservation, restoration and monitoring of the deterioration of archaeological sites. Examples from the Athenian Agora: the state prison and Omega House, and Ancient Corinth: the Fountain of the Lamps, will be used to demonstrate these possibilities.