Ribeiro planisphere of 1529

The cartographical consequences of the Portuguese and Spanish voyages of the fifteenth and early sixteenth centuries are clearly reflected in the nautical world map made in 1529 by the Portuguese map maker Diogo Ribeiro, who worked as a cosmographer in the service of the Spanish Crown. This map is a particularly lavish copy of the Padrón Real, a master sea chart that was kept at the so-called Casa de la Contratacion in Seville, where it was continually updated and served as the exemplar for the maps Spanish pilots took on board their ships. Not only does the Ribeiro planisphere depict a much greater part of the world than the portolan maps of the late Middle Ages, but it already features indications of latitude (lines for the equator and the two tropics). Making a map based on latitude measurements was more reliable than using rough estimates of the linear distances between various points. Such rough estimates are believed to have been the basis of portolan maps, but these had been projectionless in the sense that their makers did not take into account the earth’s curvature. While this was good enough for smaller areas, it began to result in inaccuracies in a body the length of the Mediterranean Sea—not to mention the coastline of an entire continent such as Africa.

Commentary. Philipp Nothaft (May-June 2019)