portolan meaning in Information Science terminology / glossary / dictionary is:
From the Italian portolano meaning “pilot book.” A detailed textual sailing guide that contains one or more graphic charts of a coastline, showing its bays, harbors, islands, and known navigational hazards but no inland features. The earliest portiolans are among the oldest known manuscript maps. Hand-drawn on vellum and of Italian origin, they date from the late 13th century and depict the Mediterranean Sea. Created by mariners from compass bearings, portolans were often more accurate than land maps of the same period. They often have rhumb lines radiating from the points of a wind rose or compass rose to help pilots chart direction (see this 16th-century example, courtesy of the Library of Congress). Place names are usually written in the interior at right angles to the line delineating the coast, with the more important ports indicated in red (see this example, courtesy of the University of Pennsylvania Library). Portolan charts were sometimes decorated (see this example). Click here to see other examples (Bell Library, University of Minnesota). Plural in Italian: portolani. Synonymous with compass chart and rhumb chart. See also: pilot.