The featured image is a photo reproduction of Carte Pisane, circa 1290, made by an unknown Italian cartographer. It is the oldest Portolan chart on record. It is named after the family that found it. Little is actually known of it. The original is currently housed in Paris, France. Its caption at the Mariner’s Museum tells us that cartographers relied on accurate geographic information to produce navigation maps, or portolan. Portolan are books that include sailing directions with charts and detailed descriptions of coasts and harbors. These charts used rhumb, or directional, lines and compass roses. Rhumb is that name of the points on a compass. In cartography it is an imaginary line on the earth’s surface that cuts through all meridians at the same angle. It is used for plotting a ship’s course on a chart. The Carte Pisane shows many different blocks of squares that originate at a specific geographic location. Today all of our maps use longitude and latitude. According to the Mariner’s Museum, longitude was not perfected and used in navigation until the 18th century, around the time of John Cook and his explorations in the Pacific.
 “Portolano.” Merriam-Webster.com. Accessed November 26, 2017. https://www.merriam-webster.com/dictionary/portolano