Skip to main content
European Commission logo print header

The Medieval and Early Modern Nautical Chart: Birth, Evolution and Use

Periodic Reporting for period 4 - MEDEA-CHART (The Medieval and Early Modern Nautical Chart: Birth, Evolution and Use)

Reporting period: 2021-12-01 to 2023-05-31

The main purpose of project Medea-Chart was to solve a series of historiographical questions that have long eluded historians of cartography, concerning the birth, technical evolution, and use of old nautical charts. Some of the historiographical issues that we aimed to clarify in this project were:
- When, where and why were the first nautical charts of the Mediterranean produced? Although there has always been a broad consensus that the earliest charts were probably made around 1200 in Italy, following the introduction of the marine compass, the supporting evidence was still scarce at the time the Medea-Chart project started.
- How were those charts constructed? There is a broad consensus among historians that the earliest charts were drawn using compass directions and estimated distance collected by pilots at sea. But the details of the construction process are mostly unknown. For example, it is still uncertain whether the first prototypes were drawn as a single cartographic unit covering the whole Mediterranean and Black Sea or as a piecewise assemblage of regional representations.
- How and when were the first latitude charts made? We know that the earliest charts based on astronomical observations were introduced by the Portuguese in the last decades of the fifteenth century. But the details of that transition are still poorly known.
- How were nautical charts used at sea? At the time the project started very few charts showing marks of use were known. New light was expected to be shed onto this subject by systematically examining a large number of medieval and early modern charts, in order to detect traces caused by dry point compasses or pencils, and by scrutinizing contemporaneous navigational treatises and rutters, searching for written references to the use of charts at sea.
After six years of research, satisfactory answers were provided to most of those historical enigmas, namely, the genesis of nautical cartography, the methods of construction and copy of medieval and early modern charts, the origin and evolution of the latitude chart and the features of the early charts as instruments for navigation.
Considerable advances have been made concerning the so-called ‘origins problem’, that is, the genesis of medieval nautical cartography in Europe: the medieval origin of portolan charts is now broadly accepted, a meaningful connection between charts and navigation was established, magnetic declination has been convincingly demonstrated to be the cause of their tilt, and most researchers agree that portolan charts were constructed using navigational data collected by pilots at sea. The possibility that more than one prototype may have been prepared during the thirteenth century, and that a primitive type of chart based on astronomical directions probably preceded the model of the earliest extant charts, were considered. Significant advances were also made in our understanding of how manuscript nautical charts and atlases were produced and copied in the medieval and early modern period. Three journal articles were produced around these subjects.
Research has also proceeded around broader issues concerning the nature and functions of nautical cartography in the early modern period. Two articles were published about the intimate connection between pre-Mercator nautical charts and marine navigation, their intrinsic geometrical incompatibility with geographical maps, and how these issues generated misunderstanding and conflict among scholars, cartographers, and pilots in the sixteenth century. A book was published containing a commented anthology of European texts of the fifteenth and sixteenth centuries, where those issues are discussed.
Some progress was made on the use of pre-Mercator charts at sea, following the planned systematic examination of hundreds of charts, using the Medea-Chart database. A journal article was published with a study of one of the earliest extant charts showing marks of use, produced at the beginning of the sixteenth century.
In contrast to what may happen in some areas of the so-called “hard sciences”, the general public have no difficulty in understanding most results of our research and often express interest in them. This was also to be expected in a region of the world (Europe, and especially Portugal) whose historical contribution to nautical sciences and geographical knowledge is very rich. That is one of the reasons why public engagement and outreach have been an important concern of our project since its very beginning. As part of this activity, weekly newspaper articles were published during five months in the leading Portuguese newspaper “Público”, later gathered in a small book. In 2019, the project leader participated, as an invited speaker, in a TEDx event, in Lisbon: Also, several interviews (radio, newspapers, Youtube) were made to the team members, all directed at the general public. During the span of a year, 52 brief articles were published online weekly, all authored by the project team members, about charts contained in the Medea-Chart database:
The end of project Medea-Chart was marked by two important events: an international workshop gathering some of the best-known world experts on the subject, where the results of the project were summarized and discussed ( ; and a public exhibition, “What is a Nautical Chart, Really” (Instituto Hidrográfico, Lisbon, Portugal), illustrating some of its most significant results.
An online information system (the Medea-Chart database) which was conceived, designed, and populated by the Medea-Chart team, with images and information of more than 6000 nautical charts and 600 atlases, is now fully operational and available worldwide to researchers and general public: The associated code was developed by our computer science expert, Ricardo Vaz.
Most of the results of Medea-Chart’s research are original and add to the present state of the art on the history of nautical cartography. The following achievements are especially significant:
- The new pieces of evidence in favour of the medieval origin of portolan charts, as instruments for navigation (Fig. 1).
- The new pieces of evidence in support of the hypothesis that the earliest portolan charts were constructed as a piecewise assemblage of regional representations (Fig. 2).
- The conclusions drawn from the study of the Liber de existencia riverierarum about the probable existence of a primitive model of nautical chart, not based on compass directions and preceding the one of Carte Pisane.
- The clarification of the copying methods used by the medieval and early modern chart makers.
- The new interpretations of the geometry and nature of pre-Mercator nautical charts as instruments for navigation, and their intrinsic incompatibility with geographical maps based on the Ptolemaic prescriptions.
- The evidence produced from the study of the anonymous Portuguese chart known as Kunstmann III, shading additional light onto the transition between the portolan chart and the latitude chart.
- The clarification of the date, authorship, and purpose of the polar chart of 1521-1524 attributed to Pedro Reinel and kept in Istanbul.
- The development of the Medea-Chart database (Fig. 3).
Carte Pisane (c.1290) with its implicit interpolated grid of meridians and parallels (BnF)
Print screen of the database showing an atlas of the sixteenth century
Latitude errors on Viladestes chart (1413), showing two distinct groups of cartographic data (BnF)