Doubly Perceived Shape of the Adriatic Sea Basin on Early Modern Geographical Maps and Nautical Charts

The implementation of graticules on geographic maps and nautical charts, initially developed in the Hellenistic period, was a rediscovered novelty to Western European cartographers of the early modern period. The research sought to computationally examine the accuracy of spherical coordinates’ data extracted from selected geographical maps and nautical charts. Research results suggest that the cartographers who made geographic maps relied significantly on Claudius Ptolemy’s data on locations but managed to make certain accuracy improvements. The nautical charts with graticules showed significantly greater longitudinal accuracy, which suggests that they were created by using other data sources as their graphical templates; most likely the portolan charts that were already in existence at the time.