New Technologies in the Processing of European Digital Heritage and Their Application to the Historical Images of the American Flight of 1944 Over Spain

Abstract

Historical aerial images constitute an invaluable heritage that requires meticulous recovery and preservation. Interest in this task has been shown at the international level, where several congresses have been held to analyse orthophotographs production techniques, as well as the state of the art of preservation and dissemination of historical material. Innovative image orthorectification models, such as Structure for Motion and Multi-View Stereo, derived from classical photogrammetric methods such as collinearity equations, Direct Linear Transformation and Rational Function Model, have shown excellent results in the creation of 3D models from images captured by mobile devices and unmanned aerial vehicles (UAVs). These advances open up a new line of research for its application in historical flights, characterised by unsuitable flight and conservation conditions, with geometries away from the conventional geometric model and the absence of orientation parameters. On the basis of the papers presented at the EuroSDR congresses in 2019 and 2022, and using SfM and MVS algorithmic programmes, research on the processes of orthorectification of historical images has been deepened, particularly in the processing of large volumes of data. The methodology was applied to what is potentially the largest block of data to date, comprising over 4,000 images covering an area of over 40,000 square kilometres corresponding to the A-series flight, carried out by the US Army Map Service between 1945 and 1946. This technical process represents a significant step towards the accurate correction of valuable historical aerial imagery, contributing to architectural study, urban planning, property organisation, and historical heritage conservation.