Portolan charts are

nautical chart A nautical chart or hydrographic chart is a graphic representation of a sea region or water body and adjacent coasts or river bank, banks. Depending on the scale (map), scale of the chart, it may show depths of water (bathymetry) and heights of ...

s, first made in the 13th century in the

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

basin and later expanded to include other regions. The word ''portolan'' comes from the Italian ''portolano'', meaning "related to

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Hamburg, Manch ...

s or harbors", and which since at least the 17th century designates "a collection of sailing directions".

Definition

The term "portolan chart" was coined in the 1890s because at the time it was assumed that these maps were related to portolani, medieval or early modern books of sailing directions. Other names that have been proposed include

rhumb line In navigation, a rhumb line, rhumb (), or loxodrome is an arc crossing all meridians of longitude at the same angle, that is, a path with constant azimuth ( bearing as measured relative to true north). Navigation on a fixed course (i.e., s ...

charts, compass charts or loxodromic charts whereas modern French scholars prefer to call them nautical charts to avoid any relationship with portolani. Several definitions of portolan chart coexist in the literature. A narrow definition includes only medieval or, at the latest, early modern sea charts (i.e. maps that primarily cover maritime rather than inland regions) that include a network of rhumb lines and do not show any indication of the use of

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

coordinates. The geographic scope of these mostly medieval portolan charts is limited to the Mediterranean and Black Seas with possible extensions to West European coasts up to Scandinavia and West African coasts down to Guinea. Some authors further restrict the term portolan chart to single-sheet maps drawn on parchment, whereas books that contain several sea charts are called nautical

atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...

es. A broader definition of portolan chart accepts any sea chart or atlas that meets the following series of stylistic requirements: drawn by hand, with a network of rhumb lines that emanate from the center of hidden circles, focused on the coasts and islands, with place names written perpendicular to the coastline on the land side and with sparse information about the interior of landmasses. This broader definition encompasses charts of potentially any sea and even maps of the entire world, which are sometimes called nautical planispheres, provided they meet the aforesaid criteria. It includes nautical charts that depict latitude scales and have been called " latitude charts" by other authors to distinguish them from proper portolan charts, which are believed to have been constructed on the basis of

dead reckoning In navigation, dead reckoning is the process of calculating the current position of a moving object by using a previously determined position, or fix, and incorporating estimates of speed, heading (or direction or course), and elapsed time. T ...

information.

Rhumb lines

Portolan charts are characterized by their rhumbline networks, which emanate out from compass roses located at various points on the map. The lines in these networks are generated by compass observations to show lines of constant bearing. Though often called rhumbs, they are better called " windrose lines": As cartographic historian Leo Bagrow states, "…the word 'loxodromic'' or ''rhumb chart''is wrongly applied to the sea-charts of this period, since a loxodrome gives an accurate course only when the chart is drawn on a suitable projection. Cartometric investigation has revealed that no projection was used in the early charts…". The straight lines shown criss-crossing portolan charts represent the sixteen directions (or headings) of the mariner's compass from a given point, which became thirty-two directions from around 1450. The principal lines are oriented to the magnetic north pole.Rehmeyer, Julie
The Mapmaker's Mystery
''Discover'', June 2014, pp. 44–49 (subscription). Thus the grid lines varied slightly for charts produced in different eras, due to the natural changes of the Earth's

magnetic declination Magnetic declination (also called magnetic variation) is the angle between magnetic north and true north at a particular location on the Earth's surface. The angle can change over time due to polar wandering. Magnetic north is the direction th ...

. These lines are similar to the compass rose displayed on later maps and charts. "All portolan charts have wind roses, though not necessarily complete with the full thirty-two points; the compass rose ... seems to have been a Catalan innovation".

Use

The portolan chart combined the exact notations of the text of the

periplus A periplus (), or periplous, is a manuscript document that lists the ports and coastal landmarks, in order and with approximate intervening distances, that the captain of a vessel could expect to find along a shore. In that sense, the periplus wa ...

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. Portolans failed to take into account the

curvature of the Earth Spherical Earth or Earth's curvature refers to the approximation of the figure of the Earth as a sphere. The earliest documented mention of the concept dates from around the 5th century BC, when it appears in the writings of Greek philosophers. ...

; as a result, they were not helpful as navigational tools for crossing the open ocean, and were replaced by later Mercator projection charts. Portolans were most useful in close quarters' identification of landmarks. ''Portolani'' were also useful for navigation in smaller bodies of water, such as the

Black Black is a color that results from the absence or complete absorption of visible light. It is an achromatic color, without chroma, like white and grey. It is often used symbolically or figuratively to represent darkness.Eva Heller, ''P ...

, or

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

Production

Most extant portolan charts from before 1500 are drawn on

vellum Vellum is prepared animal skin or membrane, typically used as writing material. It is often distinguished from parchment, either by being made from calfskin (rather than the skin of other animals), or simply by being of a higher quality. Vellu ...

, which is a high-quality type of

parchment Parchment is a writing material made from specially prepared Tanning (leather), untanned skins of animals—primarily sheep, calves and goats. It has been used as a writing medium in West Asia and Europe for more than two millennia. By AD 400 ...

, made from calf skin. Single charts were normally rolled whereas those that formed part of atlases were pasted on wood or cardboard supports. The earliest surviving explanations of how to draw a portolan chart date from the 16th century, so the techniques used by medieval mapmakers can only be inferred. The instruments available in the Middle Ages are believed to have been a ruler, a pair of dividers, a pen, and inks of various colors. Drawing probably started with the windrose lines and then the mapmaker copied the coastal outlines from some earlier chart. Place names, geographic details and decoration were added in the end.

Production centers

Two main families of portolan charts were distinguished by origin, according to 19th-century historians: Italian, developed mainly in

Genoa Genoa ( ; ; ) is a city in and the capital of the Italian region of Liguria, and the sixth-largest city in Italy. As of 2025, 563,947 people live within the city's administrative limits. While its metropolitan city has 818,651 inhabitan ...

Venice Venice ( ; ; , formerly ) is a city in northeastern Italy and the capital of the Veneto Regions of Italy, region. It is built on a group of 118 islands that are separated by expanses of open water and by canals; portions of the city are li ...

and

Rome Rome (Italian language, Italian and , ) is the capital city and most populated (municipality) of Italy. It is also the administrative centre of the Lazio Regions of Italy, region and of the Metropolitan City of Rome. A special named with 2, ...

; and Spanish, with

Palma de Mallorca Palma (, ; ), also known as Palma de Mallorca (officially between 1983 and 1988, 2006–2008, and 2012–2016), is the capital and largest city of the Autonomous communities of Spain, autonomous community of the Balearic Islands in Spain. It is ...

as a main center of production. Portuguese charts were believed to be derived from the Spanish. Arab portolan charts were not recognized until the second half of the 20th century.

Italian

The copious number of Italian portolan charts begins in the mid 13th century, with the oldest called Carta Pisana, which is kept in the National Library in Paris. To the next century belong the Carignano Chart, disappeared from the National Archive of

Florence Florence ( ; ) is the capital city of the Italy, Italian region of Tuscany. It is also the most populated city in Tuscany, with 362,353 inhabitants, and 989,460 in Metropolitan City of Florence, its metropolitan province as of 2025. Florence ...

where it had been conserved for a long time; cartographic works of the Genoese Pietro Vesconte, the illustrator of the work of Marino Sanudo; the chart of Francisco Pizigano (1373), with stylistic influence from Mallorca; and those of Beccario, Canepa and the brothers Benincasa, natives of

Ancona Ancona (, also ; ) is a city and a seaport in the Marche region of central Italy, with a population of around 101,997 . Ancona is the capital of the province of Ancona, homonymous province and of the region. The city is located northeast of Ro ...

. The fifteenth-century Luxoro Atlas, whose authorship is anonymous, is held at the Biblioteca Civica Berio in

Catalan

The Spanish introduced a novelty in nautical cartography, with geographical maps having common stylistic representation of certain accidents and locations. The masterpiece of the Majorcan portolan charts is the

Catalan Atlas The Catalan Atlas (, ) is a medieval world map, or mappa mundi, probably created in the late 1370s or the early 1380s (often conventionally dated 1375), that has been described as the most important map of the Middle Ages in the Catalan language, ...

made by Abraham Cresques in 1375, and kept in the

Bibliothèque Nationale de France The (; BnF) is the national library of France, located in Paris on two main sites, ''Richelieu'' and ''François-Mitterrand''. It is the national repository of all that is published in France. Some of its extensive collections, including bo ...

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

. Abraham Cresques was a Majorcan Jew who worked at the service of Pedro IV of Aragon. In his "buxolarum"

magnetic compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with m ...

] workshop he was helped by his son Jafuda. The Atlas is a World Map, that is, world map and regions of the Earth with the various peoples who live there. The work was done at the request of Prince John, son of Pedro IV, desirous of a faithful representation of the world from west to east. 12 sheets form the world map on tables, linked to each other by

scroll A scroll (from the Old French ''escroe'' or ''escroue''), also known as a roll, is a roll of papyrus, parchment, or paper containing writing. Structure A scroll is usually partitioned into pages, which are sometimes separate sheets of papyru ...

and screen layout. Each table measures 69 by 49 cm. The first four texts are filled with geographical and astronomical tables and calendars. The newest of the Cresques World Map is the representation of Asia, from the Caspian sea to Cathay (China), which takes into account information from Marco Polo, and Jordanus . In the 14th century, also highlights the work of Guillem Soler, which cultivates both styles, the purely nautical and nautical-geographical. To the 15th century corresponds the famous portolan chart by Gabriel Vallseca, (1439)'','' kept in the Maritime Museum of Barcelona, notable for its delicacy of execution and lively picturesque details, masked by a spot of ink left by

Frédéric Chopin Frédéric François Chopin (born Fryderyk Franciszek Chopin; 1 March 181017 October 1849) was a Polish composer and virtuoso pianist of the Romantic period who wrote primarily for Piano solo, solo piano. He has maintained worldwide renown ...

and

George Sand Amantine Lucile Aurore Dupin de Francueil (; 1 July 1804 – 8 June 1876), best known by her pen name George Sand (), was a French novelist, memoirist and journalist. Being more renowned than either Victor Hugo or Honoré de Balz ...

Portuguese

The Portuguese portolan charts come from the Majorcan tradition, and as traditional portolan charts did not fulfill the requirements demanded by the expansion of the geographic horizons attained by Portuguese and Spaniards, they superposed the astronomical lines of the equator and tropics on top of the wind line network, and they continued being elaborated over the 16th and 17th centuries.

Arab

Three medieval portolan charts written in Arabic are preserved: *Map of Ahmed ibn Suleiman al-Tangi from 1413 to 1414. *Map of Ibrahim al-Tabib al-Mursi from 1461 *Map of western Europe, anonymous and undated, preserved in the Ambrosiana Library, dating from the 14th or 15th centuries. In addition there is a detailed description of a nautical Arab map of the Mediterranean in the Encyclopedia of the Egyptian Ibn Fadl Allah al-'Umari, written between 1330 and 1348. There are also descriptions limited to smaller geographic regions, in a work of Ibn Sa'id al Maghribi (13th century) and even in the work of Al-Idrisi (12th century).

Theories of origin

The origins of portolan charts are obscure, having no known predecessors. One studyNicolai, R. (2014
A critical review of the hypothesis of a medieval origin for portolan charts
. Uitgeverij Educatieve Media concludes that portolans originated from earlier charts drawn on what is now called the Mercator projection, stating that portolans are mosaics of smaller charts, each with their own scale and orientation, and suggesting that the cartographic capabilities of whichever civilization produced the antecedent charts was more advanced than is currently acknowledged. These ideas are rejected by established researchers in the field, however, who find ample evidence of medieval origins and construction methods. It has been proposed that portolan charts evolved from the mental maps that Mediterranean pilots had used since ancient times, which had been transmitted orally over generations.

Evolution

The earliest portolan charts focused on the

and

Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...

coasts, with only partial and sometimes sketchy depiction of Atlantic coasts up to Scandinavia. In the 15th and 16th centuries, with the beginning of the

Age of Discovery The Age of Discovery (), also known as the Age of Exploration, was part of the early modern period and overlapped with the Age of Sail. It was a period from approximately the 15th to the 17th century, during which Seamanship, seafarers fro ...

, the scope of portolan charts expanded south down to the

Gulf of Guinea The Gulf of Guinea (French language, French: ''Golfe de Guinée''; Spanish language, Spanish: ''Golfo de Guinea''; Portuguese language, Portuguese: ''Golfo da Guiné'') is the northeasternmost part of the tropical Atlantic Ocean from Cape Lopez i ...

. Charts also started to be drawn by Portuguese and Spanish mapmakers for the newly explored seas in

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

America The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, South Asia and the Pacific.

References

External links

ongoing collection of essays and tabulated data by Tony Campbell, comprising about 30 separate web publications, over 120 tables and graphs, a census of surviving charts pre-1500 and a comprehensive bibliography.
J. Rey Pastor & E. Garcia Camarero ''La cartografía mallorquina''
* Images of portolan charts: *

mini-site,

University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...

*
Portolan Charts
samples from

Yale University Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...

{{DEFAULTSORT:Portolan Chart Nautical charts Manuscripts Navigational equipment