Traces of the Common Origin of Carte Pisane, Cortona Chart, and Pietro Vesconte’s Charts

• Published in: Kartographische Nachrichten 2024-06, Vol.74 (2), p.137-156
• Main Author: Marelić, Tome
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Geographical Information Systems/Cartography; Geography; Human Geography; Natural Hazards; Visualization; Web Development
• ISSN: 2524-4957; 2524-4965
• DOI: 10.1007/s42489-023-00154-6

Anonymous Carte Pisane (c. 1275) and Cortona chart (c. 1300), as well as Pietro Vesconte's charts, made in 1311 and 1313, which represent some of the earliest known portolan charts, were cartometrically analysed to examine the geometric similarities between their coastal renderings. The research results show that not only the majority of their territorial coverage was drawn very similarly to each other but also that certain parts of the coastline are nearly identical between all the examined charts. Also, the magnitude and orientation of displacement vectors of residuals revealed that the Mediterranean and Black Sea areas on charts contain seven subsections which are on average, twice as accurate in comparison to the same area treated as a whole. The fundamental conclusion is that there is a high probability that the coastline renderings on the earliest known portolan charts are, actually, more or less skilfully made copies of the same source material used as a graphic template. The hypothetical source might have been an atlas whose origins date back to before the Middle Ages, containing charts whose extents were, perhaps, similar to the extents of detected subsections, which medieval cartographers were not able to assemble correctly due to their ignorance of map projections.