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 vigorosly documented photographically and many of these photographs are available in archives. Not all photo archives, however, are suitable for photogrammetry, as they were not produced 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. Employing this methodology for sites that are still accessible provides the opportunity for quantitative comparison of the current condition of the site to the condition at the time of excavation. Used in this way, 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.

No abstract

Archaeological monuments all over the world face problems of conservation and maintenance due to natural events and processes as well as human intervention, all of which lead to their alteration and deterioration. In particular, monuments and sites that have been excavated and left exposed to the elements experience decay, which would have taken centuries prior to excavation, in just a few years when left unprotected. Thus, the necessity to detect and observe changes over time becomes paramount. Legacy data and, in particular, retrospective photogrammetric modeling, are vital tools in this process. In this work we compare two photogrammetric 3D models of the Omega House, in the Athenian Agora, to assess how much the site has changed between the time of its first excavation in 1972 and its current state. Constructive Solid Geometry (CSG) is utilized to perform Boolean operations. Additionally, distance and volume calculations are performed. The software CloudCompare was used for this work. Overall, the state of Omega House monument proves to have been preserved from 1972 to 2017, except for certain differences that are highlighted as follows: The central north part of the monument in the model 2017 presents increased volume per 7.86% in comparison with the model 1972. The northeast part of the monument in the 2017 model shows decreased volume per 5.11% when compared to the model 1972. Moreover, the calculated distances between the two models from 1972 and 2017 present the greatest values in the case of the southwest and northwest parts of the monument, ranging between −17 cm to 5 cm.

No abstract