Mapping uncertainty. Defining spatial accuracy of WWI historical sources in the Asiago Plateau (NE Italy)

Abstract

During World War I (WWI), the landscapes of the Venetian Prealps were extensively transformed by the construction of defensive lines and field fortifications. Historical sources (aerial photographs, military cartography, ground photos, panoramic drawings, and written documents) preserve evidence and memory of these changes and enable the reconstruction of the spatial organization of past military systems through Geographic Information Systems (GIS). The digitization of such sources provides an effective means to locate military features that are no longer visible in the present-day landscape. However, the spatial accuracy of digitized features remains a critical issue. The same military element, when derived from different types of historical sources, may show spatial discrepancies of tens of meters due to scale constraints, survey methods lacking topographic precision, or the physical condition of the documents. Despite a growing body of research on the use of historical sources in GIS, systematic approaches to assess and compare spatial accuracy across heterogeneous datasets are still limited.

This study investigates the positional accuracy of WWI military features through a Historical GIS database developed for the Asiago Plateau, a representative sector of the Italian Front. The database includes 60,300 features digitized from sources produced by Austro-Hungarian, British, and Italian armies. The research aims to provide a first local-scale assessment of the factors influencing spatial accuracy and their relative impact. A qualitative and semi-quantitative analysis is carried out to evaluate accuracy variations across different types of sources and to define a priority scale based on their reliability. Building on these results, the study introduces an Accuracy Level index, a semi-qualitative scale designed to assess the topographic accuracy of digitized military features. The proposed methodology represents a first step toward a replicable framework for evaluating spatial accuracy in Historical GIS databases, with potential applications to broader spatial contexts.