Portolan

Sea charts drawn on vellum that were designed to be viewed as though sailing. All portolan charts display RHUMB LINES [link to glossary entry] and one or more decorative COMPASS ROSES [link to glossary entry]. Coastal place names are written on the landside of the coastline, to avoid interfering with sailing courses. There is generally minimal detail within the interior of the landmasses. However, important cities and other features are illustrated, and islands are often shown in distinct colours.