Portolan charts are nautical charts, first made in the 13th century in the Mediterranean basin and later expanded to include other regions, which have been noted for their high cartographic accuracy.

What are Portolan Chart used for?

The portolan charts were characterized by rhumb lines, lines that radiate from the centre in the direction of wind or compass points and that were used by pilots to lay courses from one harbour to another. The charts were usually drawn on vellum and embellished with a frame and other decorations.

What information did a Portolan Chart give to sailors?

The portolan chart combined the exact notations of the text of the periplus or pilot book with the decorative illustrations of a medieval T and O map. In addition, the charts provided realistic depictions of shores. They were meant for practical use by mariners of the period.