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Portolan chart

Portolan charts are the earliest known type of nautical charts, and the oldest known examples were made in the late 13th and early 14th centuries in the Mediterranean region, usually displaying the areas between the Atlantic coasts of Western Europe and Northwestern Africa to the west and the Black Sea to the east. Besides those showing the entire area on a single map field, there are also portolan charts that show smaller territorial extents, either as separate editions or as a series of charts that together form portolan atlases.

A portolan nautical chart of the Mediterranean Sea, second quarter of the 14th century. Kept in the Library of Congress, where it is the oldest original cartographic artifact.

The word portolan comes from the Italian portolano, meaning "related to ports or harbors", and which since at least the 17th century designates "a collection of sailing directions".[1]

Portolan charts are manuscript charts rendered using ink on vellum sheets and are easily recognizable by their distinct visual characteristics, such as a content focus on coastal regions, networks of colour-coded straight lines emanating from one or more centres in 32 directions, linear scale bars calibrated in so-called portolan miles (miglio),[2] and place names inscribed perpendicular to the coastline contours. Their most perplexing features are the extremely realistic portrayal of coastlines and a complete historical lack of their evolutionary path[3] because the oldest known samples have already been made to a highly developed stage,[4][5] and later-made charts and atlases have not become more accurate over time.[6][7]

Terminology

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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.[8] Other names that have been proposed include "rhumb line charts", "compass charts" or "loxodromic charts"[3] whereas modern French scholars prefer to call them just "nautical charts" to avoid any relationship with portolani.[9]

Several definitions of portolan chart coexist in the literature. A narrow definition includes only medieval[10] or, at the latest, early modern sea charts (i.e. those that primarily focus on sea basins and coastlines, leaving the depictions of inland areas with little or no content) that include a network of rhumb lines and do not show any indication of the use of spherical coordinates, i.e. latitudes and longitudes .[11] The geographic extent 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,[12] whereas late medieval and early modern manuscript bindings that contain several nautical charts are usually called "nautical atlases" or "portolan atlases". A broader definition of portolan chart includes any manuscript nautical chart or atlas that primarily depicts coastal areas, contains a network of rhumb lines, and has place names written perpendicularly to the coastline.[13][14] This expanded definition encompasses charts of virtually any sea area and even maps of the entire world, often referred to as nautical planispheres, as long as they satisfy the aforementioned criteria. It also comprises nautical charts that depict latitude scales and have been referred to as "latitude charts" by other authors to distinguish them from typical portolan charts showing the Mediterranean, which some scholars believe were created upon a large body of shipborne bearing and distance data observed through dead reckoning navigation during the Late Middle Ages.[11]

Specific features of portolan charts

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Rhumb lines

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Main article: Rhumbline network

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…".[15]

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.[16] The principal lines are oriented to the magnetic north pole.[17] Thus the grid lines varied slightly for charts produced in different eras, due to the natural changes of the Earth's magnetic declination.[17] 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".[2]

Use

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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, and were replaced by later Mercator projection charts.[17] Portolans were most useful in close quarters' identification of landmarks.[17] Portolani were also useful for navigation in smaller bodies of water, such as the Mediterranean, Black, or Red Seas.

Production

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Most extant portolan charts from before 1500 are drawn on vellum, which is a high-quality type of parchment, made from calf skin. Single charts were normally rolled whereas those that formed part of atlases were pasted on wood or cardboard supports.[18]

The earliest surviving explanations of how to draw a portolan chart date from the 16th century,[19] 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.[20]

Production centers

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Portolan chart of 1541

Two main families of portolan charts were distinguished by origin, according to 19th-century historians: Italian, developed mainly in Genoa, Venice and Rome; and Spanish, with Palma de Mallorca 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

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

Catalan

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1439 portolan chart by Gabriel de Vallseca (Museu Maritim, Barcelona)

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 in Paris.

Abraham Cresques was a Majorcan Jew who worked at the service of Pedro IV of Aragon. In his "buxolarum" [=magnetic compass] 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 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 and George Sand.[21]

Portuguese

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Portolan chart by Jorge de Aguiar (1492), the oldest known signed and dated chart of Portuguese origin (Beinecke Rare Book and Manuscript Library, Yale University, New Haven, USA)

The Portuguese portolan charts come from the Majorcan tradition,[22] 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

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Three medieval portolan charts written in Arabic are preserved:[23]

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.[23] 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).[25]

Theories of origin

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While the production dates of portolan charts are mainly clear and undisputed, the origin of the spatial data utilised in their creation remains scientifically unresolved, as no less accurate earlier mediaeval nautical charts have been uncovered, nor have late mediaeval cartographers documented precise information on how the data underlying their creations were initially observed.[26] Consequently, there are two principal scholarly hypotheses concerning their origin: the mediaeval origins hypothesis and the pre-medieval origins hypothesis.

  • The medieval origins hypothesis, which mainly stems from a traditional descriptive approach, states that a large body of bearing and distance observations, systematically observed by sailboat navigators throughout the Mediterranean, Black Sea, and East Atlantic during their dead reckoning navigations in the late medieval period, was compiled and presented to cartographers, who then transformed it into a coherent graphical representation known as a portolan chart.[27][28][29][30]
  • The pre-medieval origins hypothesis, mainly built on the synthesis of cartometric analyses and known historical records, posits that portolan charts exhibit an accuracy that surpasses what could be expected from genuine mediaeval artefacts, indicating they are likely late medieval reproductions of some earlier-made maps or charts.[5][6][7][31][32]


One study[33] 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 were more advanced than is currently acknowledged.[34] This publication led certain researchers in the field to react to those ideas,[35][36] but the criticism was not based on sufficiently strong arguments.[37]

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.[28]

Evolution

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The earliest portolan charts focused on the Mediterranean and Black Sea 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 scope of portolan charts expanded south down to the Gulf of Guinea. Charts also started to be drawn by Portuguese and Spanish mapmakers for the newly explored seas in Africa, America, South Asia and the Pacific.

See also

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References

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  1. ^ Campbell, Tony. "'Portolan charts from the late thirteenth century to 1500' (Additions, Corrections, Updates)". Map History / History of Cartography: THE Gateway to the Subject. Retrieved 8 December 2018.
  2. ^ a b Campbell 1987, page 389
  3. ^ a b Roel, Nicolai (2016). The enigma of the origin of Portolan charts : a geodetic analysis of the hypothesis of a medieval origin. Leiden. pp. 11–12. ISBN 9789004282971. OCLC 932069190.{{cite book}}: CS1 maint: ___location missing publisher (link)
  4. ^ Marelić, Tome (2024-06-01). "Traces of the Common Origin of Carte Pisane, Cortona Chart, and Pietro Vesconte's Charts". KN - Journal of Cartography and Geographic Information. 74 (2): 137–156. Bibcode:2024JCGI...74..137M. doi:10.1007/s42489-023-00154-6. ISSN 2524-4965.
  5. ^ a b Marelić, Tome (2024-12-18). "Are Portolan Charts and Portolan Mile Geometrically Rooted in Classical Antiquity? A Cartometric Analysis of al-Shirazi's "Greek Map" and the Pisane, Lucca, Avignon, and Cortona Charts". Cartographica. 59 (4): 143–160. doi:10.3138/cart-2024-0029. ISSN 0317-7173.
  6. ^ a b Marelić, Tome (2024). "Copying-lineages of portolan chart metrics and implications of their pre-medieval origin". International Journal of Cartography. 0: 1–26. doi:10.1080/23729333.2024.2349974. ISSN 2372-9333.
  7. ^ a b Marelić, Tome (2025-03-01). "Mosaics Within Mosaics: The Geometry of Portolan Atlases that Contradicts the Medieval Origin Hypothesis". KN - Journal of Cartography and Geographic Information. 75 (1): 57–78. Bibcode:2025JCGI...75...57M. doi:10.1007/s42489-024-00176-8. ISSN 2524-4965.
  8. ^ Campbell 1987, page 375
  9. ^ Vagnon, Emmanuelle (2013). "La représentation cartographique de l'espace maritime". In Gautier Dalché, Patrick (ed.). La Terre connaissance, représentations, mesure au Moyen Âge (in French). Brepols. ISBN 978-2-503-54753-4.
  10. ^ For example, Ramon Pujades only considers charts earlier than 1470 in his census.Pujades i Bataller, Ramon Josep (2007). Les cartes portolanes: la representació medieval d'una mar solcada. Institut Cartogràfic de Catalunya, l’Institut d’Estudis Catalans i l’Institut Europeu de la Mediterrània. ISBN 978-84-393-7576-0.
  11. ^ a b Gaspar, Joaquim Alves (June 2013). "From the Portolan Chart to the Latitude Chart: The silent cartographic revolution" (PDF). CFC (216): 67–77.
  12. ^ Delano-Smith, Catherine (7–8 June 2018). Emergent Maps: Questioning the Rise and Function of the Portolan Chart and the Regional Map in the Middle Ages. Second International Workshop on the Origin and Evolution of Portolan Charts. Lisbon.
  13. ^ Pflederer, Richard (2009). Census of Portolan Charts and Atlases. Privately printed.
  14. ^ Campbell, Tony (18 November 2016). "Cartographic innovations by the early portolan chartmakers". Map History / History of Cartography: THE Gateway to the Subject. Retrieved 8 December 2018.
  15. ^ Leo Bagrow (2010). History of Cartography. Transaction Publishers. p. 65. ISBN 978-1-4128-2518-4.
  16. ^ Campbell 1987, page 396
  17. ^ a b c d Rehmeyer, Julie. The Mapmaker's Mystery, Discover, June 2014, pp. 44–49 (subscription).
  18. ^ Campbell 1987, page 376
  19. ^ For example Martín Cortés, Arte de navegar, 1551
  20. ^ Campbell 1987, pages 391-392
  21. ^ George Sand (1843). Oeuvres complètes de George Sand. Perrotin. pp. 69–.
  22. ^ Estudos de História, Volume III. UC Biblioteca Geral 1. pp. 10–. GGKEY:7186FCQBHS5.
  23. ^ a b Ducène, Jean-Charles (2013-06-01). "Le portulan arabe décrit par Al-'Umari" (PDF). CFC (216): 81–90.
  24. ^ Herrera Casais, Mónica. 'The 1413-14 sea chart of Ahmad al-Ţanjī', in: Emilia Calvo, Mercè Comes, Roser Puig & Mónica Rius (eds) A shared legacy: Islamic science East and West. Homage to Prof. J.M. Millàs Vallicrosa (Barcelona: Universitat de Barcelona, 2008) pp.283-307.
  25. ^ a b Vernet Ginés, John (1962). "The Maghreb in the Biblioteca Ambrosiana Chart". 16: 1–16. {{cite journal}}: Cite journal requires |journal= (help)
  26. ^ Campbell 1987, page 380
  27. ^ Pujades i Bataller, Ramon J. (2007). Les cartes portolanes: la representació medieval d'una mar solcada. Institut Cartogràfic de Catalunya (1. ed.). Barcelona: Inst. Cartogràfic de Catalunya. ISBN 978-84-9785-414-6.
  28. ^ a b Campbell, Tony (2021). "Mediterranean portolan charts: their origin in the mental maps of medieval sailors, their function and their early development". Retrieved 6 October 2021.
  29. ^ Gaspar, Joaquim Alves (2025-01-02). "The origin of nautical cartography: certitudes, doubts, and perplexities". International Journal of Cartography. 11 (1): 63–92. Bibcode:2025IJCar..11...63G. doi:10.1080/23729333.2023.2240902. ISSN 2372-9333.
  30. ^ Puchades i Bataller, Ramon Josep (2023). Els Mapamundis baixmedievals: del naixement del mapamundi híbrid a l'ocàs del mapamundi portolà (Primera edició ed.). Barcelona: Generalitat de Catalunya ICGC, Institut Cartogràfic i Geològic de Catalunya. ISBN 978-84-19695-27-7.
  31. ^ Nicolai, Roel (2016). The enigma of the origin of Portolan charts: a geodetic analysis of the hypothesis of a medieval origin. History of science and medicine library. Leiden ; Boston: Brill. ISBN 978-90-04-28297-1.
  32. ^ Nicolai, Roel (2024). "The origin problem of nautical cartography: the importance of evidence and method". International Journal of Cartography. 0: 1–25. doi:10.1080/23729333.2024.2352822. ISSN 2372-9333.
  33. ^ Nicolai, R. (2014) A critical review of the hypothesis of a medieval origin for portolan charts Archived 2022-06-14 at the Wayback Machine. Uitgeverij Educatieve Media
  34. ^ Jacobs, Frank (10 March 2014). "Portolan Charts 'Too Accurate' to be Medieval". Big Think. Retrieved 30 August 2018.
  35. ^ Gaspar, Joaquim Alves (2015). "Review of Roel Nicolai's article by Joaquim Alves Gaspar". Maps in History. 53.
  36. ^ Campbell, Tony (2015). "Review of Roel Nicolai's article by Tony Campbell". Maps in History. 53.
  37. ^ Nicolai, Roel (September 2015). "How Old are Portolan Charts Really?". Maps in History 54. The Brussels Map Circle.

Further reading

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  1. Konrad Kretschmer, Die italienischen Portolane des Mittelalters, Ein Beitrag zur Geschichte der Kartographie und Nautik, Berlin, Veröffentlichungen des Instituts für Meereskunde und des geographischen Instituts an der Universität Berlin, Vol. 13, 1909. (available online)
  2. Alessandra D. Debanne, Lo Compasso de navegare. Edizione del codice Hamilton 396 con commento linguistico e glossario, Brussels, Peter Lang for the Gruppo degli italianisti delle Università francofone del Belgio, 2011.
  3. Patrick Gautier Dalché, Carte marine et portulan au XIIe siècle. Le Liber de existencia rivieriarum et forma maris nostri Mediterranei, Pise, circa 1200, Roma, École Française de Rome, 1995. (available online)
  4. Tony Campbell, "Portolan Charts from the Late Thirteenth Century to 1500", Chapter 19 of The History of Cartography, Volume I. U. of Chicago Press, 74th edition (May 15, 1987). (available online)
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