Mercator’s world map provided a representation of the surface of the earth called the Mercator projection, which allowed navigators into modern times to plot a course of travel along lines that follow a constant and single compass bearing and that appear on a map as straight and equally spaced instead of curved.

How can one represent a curving three-dimensional space such as Earth on a two-dimensional surface without distorting the image? This problem may appear astonishingly simple in the age of digital technologies, but it was more than a simple aesthetic dilemma for Renaissance artists, geographers, and mathematicians. For cartographers such as Gerardus Mercator, the question of projecting an accurate image of the world onto the two-dimensional surface of a map or nautical chart had been a preoccupation since the great second century Alexandrian geographer Ptolemy first attempted to depict Earth on a map. Map of the world, publication of
Mercator, Gerardus
Gemma Frisius, Reiner
Ortelius, Abraham
Frisius, Reiner Gemma
Finé, Oronce
Münster, Sebastian
Ortelius, Abraham
Mercator, Gerardus

A condensed version of Mercator’s 1569 wall map of the world, Nova descriptio, as produced several years later by his son, Rumold Mercator.

(Corbis)

At the heart of this problem of representation lies two functions of a map: It is both a representation of space that gives shape and form to a space one imagines and also a tool that can be used to navigate and travel within the space represented.

The publication of Mercator’s world map in Duisberg in 1569 was an event whose significance would be felt long after the cartographer’s death. Mercator’s career as a cartographer began in Louvain, where he worked alongside one of the greatest astronomers of the Low Countries, Reiner Gemma Frisius. In Frisius’s workshop, the two worked to produce terrestrial and celestial globes (1537). Also, Mercator developed his skills as an engraver and as a maker of astronomical instruments.

The sixteenth century, which followed the century that included the discoveries of Christopher Columbus and other world explorers, witnessed extraordinary accomplishments in the production and technology of mapmaking. The rediscovery and new editions of Ptolemy’s Geographike hyphegesis and the first published accounts of exploration narratives of the New World prompted cartographers such as Mercator, Frisius, Oronce Finé in France, and Sebastian Münster in Germany to produce increasingly accurate national atlases, topographical maps, nautical charts, and world maps. The new technologies of print culture (the printing press as well as woodcut and copper plate engraving) that accompanied this effervescence in map production allowed mapmakers and authors to quickly reproduce illustrated texts in significant quantities and to disseminate them to the public at a more reasonable cost. Printing;map production Also, print technology was of particular interest to sixteenth century cartographers because it allowed them to incorporate the most recent data from territorial surveys and the exploration of the Americas into their maps and to update their charts for accuracy.

Mercator’s first world map, Orbis imago
Orbis imago (Mercator) (1538), depicted the image of the world in the form of two mirrored hearts. In the language of cartography, any representation of a round body, like the earth, onto a flat surface is called a map projection. Mercator’s first world map used a double cordiform projection, a representation of the world shaped like a heart that had already been used by the French cartographer Oronce Finé in 1531. Although Mercator’s map resembled Finé’s earlier cordiform projections, it actually bore greater resemblance to Frisius’s terrestrial globe.

An important innovation in Mercator’s world map was his use of the names “North America” and “South America” (Americae pars septemtrionalis and Americae pars meridionalis), the first time these words had been used on a map. Although Mercator’s first map innovatively projected the spherical form of the earth onto the flat surface of the map, it was extremely difficult to interpret and its capacity to function as a navigational tool was hampered by the tremendous distortion that occurred around the poles.

Beginning in 1540, Mercator set out to produce a lightweight globe that could be used by navigators at sea. The concept behind the production of this globe and also his world map of 1569 was to reduce the distortion in the higher latitudes near the poles and to allow navigators to follow lines of constant and straight compass direction, known as rhumb lines. Unlike his fellow cartographer, Abraham Ortelius, whose atlas Theatrum orbis terrarum
Theatrum orbis terrarum (Ortelius) (1570) attempted to represent more realistic images of the shape of the world and its territories, Mercator was less interested in producing an accurate graphic image of the earth than producing a map that would facilitate navigation.

Published in August of 1569 and dedicated to Duke Wilhelm of Cleves, Mercator’s second world map, Nova et aucta orbis terrae descriptio ad usum navigantium emendate accomodata (also known as Nova descriptio
Nova descriptio (Mercator) ; new and more accurate description of the world properly adapted for the use of navigators), was a wall-map produced from copper plate engravings. Measuring 51.5 by 82 inches (131 by 208 centimeters) over 18 separate sheets, this was the largest map Mercator had ever produced, and it included incredible detail, extensive commentary in legends, and place-names lettered in italics.

Because calculus had yet to be invented, there has been much conjecture about how Mercator developed his new projection in view of the complicated mathematics involved in its production. It is generally accepted that Mercator developed the projection by experimenting with the spacing of meridians and parallels on his 1541 globe. In the Nova descriptio, the meridians (great circles on the surface of the earth that pass through the poles) were represented as perpendicular to the equator. Mercator then augmented the parallels of latitude progressively from the equator to the poles to attenuate the distortion of lands situated close to the higher latitudes.

With his map, Mercator was able to straighten the lines that are naturally curved and to produce networks of straight lines of latitude and longitude, or graticule. His map facilitated ease in navigation, yet as a graphic representation of the world, the continents of North America, Europe, and Asia appeared as enormous masses that occupied nearly half of the northern hemisphere, and the southern continents of South America and Africa appeared as diminutive land masses to the south. The effect of this distortion was that Greenland appeared equivalent in size to China. Although to the modern eye, the image of the world appears even more distorted than in other sixteenth century map projections and somehow less navigable, Mercator’s invention of the conformal map projection would nevertheless prove to be the most reliable and accurate guide that navigators would use through the present day.

Four maps from Mercator’s eighteen-sheet world map of 1569 appeared in Abraham Ortelius’s atlas published between 1570 and 1612. Bernard van den Putte also published the entire map in a full-size woodcut edition in 1574. The projection was effectively launched in 1599 when an English cartographer, Edward Wright of Cambridge, published a table of the divisions of meridians based on Mercator’s map. Wright’s Certaine Errors in Navigation (1599) allowed Mercator’s innovative projection to be disseminated to cartographers in the centuries that followed.

Although there was no single map projection in the sixteenth century favored or universally adopted by cartographers as the correct projection of the earth, Mercator’s world map of 1569 came to be preferred by navigators from the eighteenth century through the twenty-first century. Virtually all nautical charts use Mercator’s projection to plot steady compass courses along rhumb lines. Yet, despite the practical advantages and historical significance of Mercator’s map projection, it continues to spark controversy. As recently as the 1970’, the distortion and larger size given to the continents in the northern hemisphere on Mercator’s map prompted the publication of a map projection in Germany by Arno Peters, called the Peters projection, which attempted to correct Mercator’s distortion of the relative size of continents.

• Broc, Numa. La Géographie de la Renaissance, 1420-1620. Paris: Editions du C.T.H.S., 1986. A history of the development and technology of geography in the Renaissance.
• Crane, Nicholas. Mercator: The Man Who Mapped the Planet. New York: H. Holt, 2003. A biographical overview of Mercator’s life and contributions to the scientific development of cartography in the sixteenth century.
• Karrow, Robert W., Jr. Mapmakers of the Sixteenth Century and Their Maps: Biographies of the Cartographers of Abraham Ortelius, 1570. Chicago: Speculum Orbis Press, 1993. A detailed catalog of maps and biographies of sixteenth century mapmakers who contributed to the production of Ortelius’s atlas.
• Mercator, Gerhard. The Mercator Atlas of Europe: Facsimile of the Maps by Gerardus Mercator Contained in the “Atlas of Europe,” Circa 1570-1572. Edited by Marcel Watelet. Translated by Simon Knight. Pleasant Hill, Oreg.: Walking Tree Press, 1998. A facsimile edition of Mercator’s original maps of Europe, with commentary.
• Osley, A. S. Mercator: A Monograph on the Lettering of Maps, etc., in the Sixteenth Century Netherlands, with a Facsimile and Translation of His Treatise on the Italic Hand and a Translation of Ghim’s “Vita Mercatoris.” London: Faber & Faber, 1969. This volume contains an overview of Mercator’s important contributions to cartography, a facsimile and translation of Mercator’s treatise on italic lettering, and a translation of the only contemporary biography of Mercator by Walter Ghim.
• Snyder, John Parr, Flattening the Earth: Two Thousand Years of Map Projections. Chicago: University of Chicago Press, 1993. A history of map projection from ancient Greece through the twentieth century.
• Wilford, John Noble. The Mapmakers. Rev. ed. New York: Alfred A. Knopf, 2000. A history of mapmaking from antiquity to the present that explains the importance of Mercator’s projection method.

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