Revisiting sixteenth-century oval maps with a cartographic strain analysis

A recent research on Matteo Ricci’s 1602 Chinese World Map raised, among other issues, the question of the oval graticule used before as the projection reference of the map representation. Here, we go back to the origin of the oval graticules, which almost dominated the imaging of the sixteenth-century cartography from the Contarini-Rosselli’s map in the earliest of the century to the Ortelius and Ricci maps in its latest and the beginning of seventeenth century, inspiring again many map projection makers in the twentieth century. In this paper, the revisiting and overview of the oval graticule settings of some representative sixteenth-century maps of this category are followed by studying the relevant metrical and deformational properties, carried out on a family set of these ovals (the ‘Agnese set’ of ovals), involving tools from the cartographic strain analysis. The results give some further insights on this important category of maps, typical of a period in cartography marked by the transition from the Ptolemaean standards to the post- and meta-Ptolemaean era of map representations.