Exploring cartographic genealogies through deformation analysis: case studies on ancient maps and synthetic data

This paper presents a new methodology for identifying copying relationships in maps through cartographic deformation analysis, and introduces a novel approach for the creation of synthetic datasets for evaluation. Challenging traditional approaches that compare historical maps to modern ones for an accuracy assessment, this study focuses on the comparison between old maps through a modern reference map to identify copying processes. Using a synthetic dataset of deformed maps, this research introduces a novel way to assess deformation analysis results. The methodology’s effectiveness is demonstrated through experiments on the synthetic dataset and on five maps of Jerusalem where copying relationships are known, revealing that cosine similarity, filtered with vectors’ norm and combined with their ratio, offers a good discriminative power between maps that are complete copies and those which are not. The methodology, with the selected metric, is applied to a selection of fifty 19th-century maps of Jerusalem and used to create a hierarchical clustering. This approach enables the identification of complete copies of varying quality within large map collections. This study not only advances cartometric methodologies but also lays the groundwork for future research on the automatic detection of map lineages, marking progress toward the genealogical analysis of large cartographic datasets.