Capturing the Past for the Future: an Evaluation of the Effect of Geometric Scan Deformities on the Performance of Aerial Archival Media in Image‐based Modelling Environments

Image‐based modelling (IBM) applications can be used to successfully extract two‐ and three‐dimensional information from historic aerial and satellite imagery for use in archaeological and other landscape‐oriented research. The robust and highly automated nature of these applications can allow for image matching and dense scene reconstruction, even when input images lack information necessary for processing in traditional photogrammetric workflows. However, the overall quality of the content derived from IBM applications can be directly influenced by a number of variables, including the manner in which archival content is digitized. Significant geometric distortion can be induced in the scanning process when using non‐photogrammetric scanning devices, which can have a negative effect on the subsequent processing of scanned imagery and accuracy of derived content such as orthomosaics and digital elevation models (DEMs). While this is a well‐known issue for users of high end photogrammetry packages, the advent of IBM applications has brought the use of photogrammetric‐style techniques to a wider audience who may not be aware of the impact that geometric errors of this nature can have on the quality of derived data products. This issue is demonstrated here using a set of degraded historic World War II (WWII) Allied reconnaissance photographs that have been digitized on both photogrammetric and non‐photogrammetric platforms and subsequently processed in a well‐known IBM application using identical processing parameters. The results are compared to those from a recently collected set of vertical stereopairs and an airborne laser scan derived DEM.