(University of Waterloo, Waterloo, Canada)

Keywords: photogrammetry, 3D modelling, archival photographs, archaeology

In the past decade the use of photogrammetry to produce 3D modelling of archaeological sites has seen rapid growth and acceptance due to a significant reduction in cost and labour. While this bodes well for having accurate modelling available in the future, past excavations could benefit from similar treatment. Fortunately archaeological research has a long history of requiring comprehensive photographic documentation and in many cases the photographs have significant overlap, enabling their use in photogrammetry to produce 3D models. Some, at the time, were taken with the intention of using photogrammetry to create topographic maps. Now, with the use of these maps we can reverse the procedure to georeference the photographs in order to create properly scaled phototextured models.
This paper addresses the advantages as well as the obstacles in practicing retrospective photogrammetry based on archival photos and examines how the results can be put to use. 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, measure them and view them from angles that were never photographed and may not even exist any longer.
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 modelling will have impacts in preservation, restoration and monitoring of deterioration of archaeological sites. Examples from the Athenian Agora and Ancient Corinth will be used to demonstrate these possibilities.

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This paper demonstrates how current technologies can be combined with past documentation to produce results that demonstrate the ongoing worth and purpose of archives

The innovation is the re-use of archival data in order to produce 3D models.