Portolan charts are

nautical chart A nautical chart is a graphic representation of a sea area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land ( topographic map), natural features of the seabed, details of the coa ...

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 north by Western and Southern Europe and Anatolia, on the south by North Africa, and on th ...

basin and later expanded to include other regions. The word ''portolan'' comes from the Italian ''portulano'', 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 ...

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 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 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 the south pole to 90° at the north po ...

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 let ...

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 maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geograp ...

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 planisphere Seamanship is the art, knowledge and competence of operating a ship, boat or other craft on water. The'' Oxford Dictionary'' states that seamanship is "The skill, techniques, or practice of handling a ship or boat at sea." It involves topics a ...

s, provided they meet the aforesaid criteria. It also 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 information.

Rhumb lines

Portolan charts are characterized by their rhumbline networks, which emanate out from

compass rose A compass rose, sometimes called a wind rose, rose of the winds or compass star, is a figure on a compass, map, nautical chart, or monument used to display the orientation of the cardinal directions (north, east, south, and west) and their int ...

s 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. These lines are similar to the

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 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; as a result, they were not helpful as navigational tools for crossing the open ocean, being replaced by later

Mercator projection The Mercator projection () is a cylindrical map projection presented by Flemish geographer and cartographer Gerardus Mercator in 1569. It became the standard map projection for navigation because it is unique in representing north as up and so ...

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 which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white ha ...

, or

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

Production

Most extant portolan charts from before 1500 are drawn on

vellum Vellum is prepared animal skin or membrane, typically used as writing material. Parchment is another term for this material, from which vellum is sometimes distinguished, when it is made from calfskin, as opposed to that made from other ani ...

, which is a high-quality type of

parchment Parchment is a writing material made from specially prepared untanned skins of animals—primarily sheep, calves, and goats. It has been used as a writing medium for over two millennia. Vellum is a finer quality parchment made from the skins o ...

, made from

calf Calf most often refers to: * Calf (animal), the young of domestic cattle. * Calf (leg), in humans (and other primates), the back portion of the lower leg Calf or calves may also refer to: Biology and animal byproducts *Veal, meat from calves ...

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 ( ; it, Genova ; lij, Zêna ). is the capital of the Regions of Italy, Italian region of Liguria and the List of cities in Italy, sixth-largest city in Italy. In 2015, 594,733 people lived within the city's administrative limits. As of t ...

Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto region. It is built on a group of 118 small islands that are separated by canals and linked by over 400 bridges. The isla ...

and

Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus ( legendary) , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg , map_caption ...

; and Spanish, with

Palma de Mallorca Palma (; ; also known as ''Palma de Mallorca'', officially between 1983–88, 2006–08, and 2012–16) is the capital and largest city of the autonomous community of the Balearic Islands in Spain. It is situated on the south coast of Mallorc ...

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 ( ; it, Firenze ) is a city in Central Italy and the capital city of the Tuscany region. It is the most populated city in Tuscany, with 383,083 inhabitants in 2016, and over 1,520,000 in its metropolitan area.Bilancio demografico ...

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 in central Italy, with a population of around 101,997 . Ancona is the capital of the province of Ancona and of the region. The city is located northeast of Rome, on the Adriatic ...

. 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 made by Abraham Cresques in 1375, and kept in the

Bibliothèque Nationale de France The Bibliothèque nationale de France (, 'National Library of France'; BnF) is the national library of France, located in Paris on two main sites known respectively as ''Richelieu'' and ''François-Mitterrand''. It is the national reposito ...

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. ...

. Abraham Cresques was a Majorcan Jew who worked at the service of

Pedro IV of Aragon Peter IV, ; an, Pero, ; es, Pedro, . In Catalan, he may also be nicknamed ''el del punyalet'': "he of the little dagger". ( Catalan: ''Pere IV''; 5 September 1319 – 6 January 1387), called the Ceremonious (Catalan: ''el Cerimoniós''), ...

. In his "buxolarum" magnetic compass">Magnetic_Compass.html" ;"title="Magnetic Compass">magnetic compassworkshop 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 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 Caspian can refer to: *The Caspian Sea *The Caspian Depression, surrounding the northern part of the Caspian Sea *The Caspians, the ancient people living near the Caspian Sea * Caspian languages, collection of languages and dialects of Caspian p ...

sea to

Cathay Cathay (; ) is a historical name for China that was used in Europe. During the early modern period, the term ''Cathay'' initially evolved as a term referring to what is now Northern China, completely separate and distinct from China, which ...

(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 solo piano. He has maintained worldwide renown as a leadin ...

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. One of the most popular writers in Europe in her lifetime, bein ...

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 Ibrahim ( ar, إبراهيم, links=no ') is the Arabic name for Abraham, a Biblical patriarch and prophet in Islam. For the Islamic view of Ibrahim, see Abraham in Islam. Ibrahim may also refer to: * Ibrahim (name), a name (and list of people w ...

from 1461 *Map of western Europe, anonymous and undated, preserved in the

Ambrosiana Library The Biblioteca Ambrosiana is a historic library in Milan, Italy, also housing the Pinacoteca Ambrosiana, the Ambrosian art gallery. Named after Ambrose, the patron saint of Milan, it was founded in 1609 by Cardinal Federico Borromeo, whose a ...

, 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

, states that portolans are mosaics of smaller charts, each with their own scale and orientation, and suggests 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, and which were transmitted orally over generations.

Evolution

The earliest portolan charts focused on the

and

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean 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 bounded by Bulgaria, Georgia, ...

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 (or the Age of Exploration), also known as the early modern period, was a period largely overlapping with the Age of Sail, approximately from the 15th century to the 17th century in European history, during which seafari ...

, the scope of portolan charts expanded south down to the

Gulf of Guinea The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean from Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian (zero degrees latitude and longitude) is in the ...

. 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 in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

, America, 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, formally the University of Minnesota, Twin Cities, (UMN Twin Cities, the U of M, or Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Tw ...

*
Portolan Charts
samples from

Yale University Yale University is a Private university, private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the List of Colonial Colleges, third-oldest institution of higher education in the United Sta ...

{{DEFAULTSORT:Portolan Chart Map types Manuscripts Navigational equipment