The marine chart by Fra Mauro (active ca. 1430-ca. 1459/1464) is a large-scale map composed by three parchment sheets with a combined area of 132.5 x 75 centimeters (roughly 52.1 x 29.5 inches). It is laid out centered on a wind rose positioned on the west coast of the Peloponnese, just off the island of Zante. The map shows the Mediterranean Sea, the Black Sea, and the territories of Europe, northern Africa, and part of Asia. Like his more famous world map, Fra Mauro’s marine chart is oriented with south at the top. The scale of miles on the right edge of the map indicates the scale to be approximately 1:6,500,000. Each segment of the scale represents 50 miles and is subdivided into five parts.
In contrast to the so-called portolan charts which display only coastal outlines and use a dense nomenclature of ports and berths, Fra Mauro’s marine chart contains a great deal of chorographic information about the terrestrial interior, including rivers, cities, and monuments, along with numerous cartouches whose content and graphic characteristics suggest strong affinities with Fra Mauro’s world map. In fact, the marine chart can be perfectly superimposed on the world map, which presents the same 11-degree counter-clockwise disorientation off geographic north. This is a common characteristic of marine charts derived from topographic measurements conducted by compass, which were oriented according to the declination of the magnetic needle. The marine chart and world map are clearly derived from the same preparatory drawing, which Fra Mauro composed following nautical practice rather than humanist tradition. He established the geographical position of locations on his maps on the basis of distance and rhumb lines rather than according to geographical coordinates of longitude and latitude.