The Mercator world map of 1569 is titled (Renaissance Latin for "New and more complete representation of the terrestrial globe properly adapted for use in navigation"). The title shows that Gerardus Mercator aimed to present contemporary knowledge of the geography of the world and at the same time 'correct' the chart to be more useful to sailors. This 'correction', whereby constant bearing sailing courses on the sphere (rhumb lines) are mapped to straight lines on the plane map, characterizes the Mercator projection. While the map's geography has been superseded by modern knowledge, its projection proved to be one of the most significant advances in the history of cartography, inspiring the 19th century map historian Adolf Nordenskiöld to write "The master of Rupelmonde stands unsurpassed in the history of cartography since the time of Ptolemy."Nordenskiöld Facsimile Atlas, p.23 The projection heralded a new era in the evolution of navigation maps and charts and it is still their basis.
The map is inscribed with a great deal of text. The framed map legends (or cartouches) cover a wide variety of topics: a dedication to his patron and a copyright statement; discussions of rhumb lines; great circles and distances; comments on some of the major rivers; accounts of fictitious geography of the north pole and the southern continent. The full Latin texts and English translations of all the legends are given below. Other minor texts are sprinkled about the map. They cover such topics as the magnetic poles, the prime meridian, navigational features, minor geographical details, the voyages of discovery and myths of giants and cannibals. These minor texts are also given below.
A comparison with world maps before 1569 shows how closely Mercator drew on the work of other cartographers and his own previous works, but he declares (Legend 3) that he was also greatly indebted to many new charts prepared by Portuguese and Spanish sailors in the portolan tradition. Earlier cartographers of world maps had largely ignored the more accurate practical charts of sailors, and vice versa, but the age of discovery, from the closing decade of the fifteenth century, stimulated the integration of these two mapping traditions: Mercator's world map is one of the earliest fruits of this merger.
Extant copies and facsimiles Mercator's 1569 map was a large planisphere,Planisphere here means a rendering of the sphere onto the plane. It has no relation to the star charts as described in the article planisphere. i.e. a projection of the spherical Earth onto the plane. It was printed in eighteen separate sheets from copper plates engraved by Mercator himself.See the biography of Mercator by Iris Kockelberg in Mercator: Exploring New Horizons, pp95 –99. Each sheet measures 33×40 cm and, with a border of 2 cm, the complete map measures 202×124 cm. All sheets span a longitude of 60 degrees; the first row of 6 sheets cover latitudes 80°N to 56°N, the second row cover 56°N to 16°S and the third row cover 16°S to 66°S: this latitude division is not symmetric with respect to the equator thus giving rise to the later criticism of a Euro-centric projection.Monmonier, Chapter 10 and notes at page 200.
It is not known how many copies of the map were printed, but it was certainly several hundred.The records of the Plantin Press show that they sold at least 185 copies of the 1569 map in the period 1569–1576 alone. See Leon Voet, Les relations commerciales entre Gerardus Mercator et la maison Plantiniene à Anvers in Duisberger Forschungen, pp.171–232, and Dirk Imhof in Mercator: exploring new horizons, pp105 –107. Despite this large print run, by the middle of the nineteenth century there was only one known copy, that at the Bibliothèque Nationale de France. A second copy was discovered in 1889 at the Stadt Bibliothek of BreslauThe collections of the Stadt Bibliothek of Breslau, now the library of the University of Wrocław, are described at along with maps of Europe and Britain. These three maps were destroyed by fire in 1945 but fortunately copies had been made before then.Heyer, A. Drei Karten–Mercator in der Breslauer Stadt-Bibliotek. Zeitschrift fur Wissenschaftliche Geographie herausgegeben von J.I.Kettler, vol VII (1890), pp. 379, 474, 507. A third copy was found in a map collection Mappae Geographiae vetustae from the archives of the Amerbach family which had been given to the library of the University of Basel. The only other complete copy was discovered at an auction sale in Luzern in 1932 and is now in the map collection of the Maritiem Museum Rotterdam. van 't Hoff (1961), p.19 In addition to the complete copies there is a single page showing the North Atlantic in the Mercator atlas of Europe in the British Library.Mercator 1570 atlas, Plate 14 Many paper reproductions of all four maps have been made. Those at full scale, providing access to the detail and the artistry of Mercator's engraving, are listed next. Images of the Basil, Paris, and Rotterdam impressions can be found online.
Basel map The Basel map is the cleanest of the three extant versions. It is called the 'three strip' version because it is in three separate rows rather than a single assembled sheet. It was photographically reproduced at a reduced scale by Wilhelm Kruecken in 1992; more recently (2011) he has produced a full-scale and full sized (202×124 cm) reproduction of the map along with a five volume account (in German) covering all aspects of Mercator's work.The publications of Wilhelm Krucken are available from the home page of his web site at Ad maiorem Gerardi Mercatoris gloriam. Medium resolution scans of the separate sheets and a composite of all 18 scans are accessible as follows. Links to the individual sheets: 123456789101112131415161718
Composite image of all 18 sheets as a 20 MB file
Paris map The Paris copy is a single combined sheet that came into the possession of the Bibliothèque Nationale from the estate of Julius Klaproth (1783–1835).van 't Hoff (1961), page 40. The map is uncoloured, partially borderless and in poor condition due to repeated exhibitions during the nineteenth century. It was reproduced by Edmé-François Jomard (1777–1862) between 1842 and 1862 as part of a collection of 21 facsimile maps. Very few copies of this facsimile are known.
The Bibliothèque Nationale has put a digital image of their copy into the public domain in the form of 13 separate images. The images do not correspond exactly with the 18 original sheets: they are in three rows of different heights with 5, 4, 4 images respectively. The zoomable images permit examination of small sections of the map in very great detail. These are the only online images at a high enough resolution to read the smallest text.
Breslau map Immediately after its discovery in 1889 the Breslau map was described by Heyer who initiated copies (in multiple sheets) for the Berlin Geographical Society in 1891.Heyer, A. Drei Karten von Europa, Britische Inseln, Weltkarte, herausgegeben von der Gesellschaft fur Erdkunde. Berlin 1891. Forty years later, in 1931, a further 150 copies were issued by the Hydrographic Bureau
Rotterdam map This copy in the Maritiem Museum Rotterdam is in the form of an atlasThe term atlas, as a collection of maps, was not used for this volume. It was first applied to the Mercator atlas of 1594. constructed by Mercator for his friend and patron Werner von Gymnich.van 't Hoff (1961), p.19 It was made by Mercator in (or shortly after) 1569 by dissecting and reassembling three copies of his original wall map to create coherent units such as continents or oceans or groups of legends.Monmonier Figure 4.2, page 51 There are 17 non-blank coloured pages which may be viewed online (and zoomed to a medium resolution, much lower than that of the French copy at the Bibliothèque Nationale).A digital copy of this map may be viewed online at Maritiem Digitaal
In 1962 a monochrome facsimile of this atlas was produced jointly by the curators of the Rotterdam museum and the cartographic journal Imago Mundi.van 't Hoff (1961), The plates are accompanied with comprehensive bibliographic material, a commentary by van 't Hoff and English translations of the Latin text from the Hydrographics Review. More recently, in 2012, the Maritiem Museum Rotterdam produced a facsimile edition of the atlas, with an introduction by Sjoerd de Meer.Sjoerd de Meer, Rotterdam Facsimile of Mercator map.
World and regional maps before 1569
Principal features of the 1569 Mercator map
Mercator's projection
In Legend 3 Mercator states that his first priority is "to spread on a plane the surface of the sphere in such a way that the positions of places shall correspond on all sides with each other, both in so far as true direction and distance are concerned and as correct longitudes and latitudes". He goes on to point out the deficiencies of previous projections,Some of the projections used in the period before 1569 are shown in the gallery. They are discussed in Snyder (Flattening the Earth Chapter 1 ) and also in his article in the History of Cartography. particularly the distortion caused by the oblique incidence of parallels and meridians which gives rise to incorrect angles and shapes: therefore he adopts parallel meridians and orthogonal parallels. This is also a feature of sixteenth-century plane charts (equirectangular projections) but they also have equally spaced parallels; in Legend 3 Mercator also emphasizes the distortion that this gives rise to. In particular, the straight lines emanating from the compass roses are not rhumb lines so that they do not give a true bearing. Nor was it straightforward to calculate the sailing distances on these charts. Mariners were aware of these problems and had evolved rules of thumb to enhance the accuracy of their navigation.
Mercator presents his remedy for these problems: "We have progressively increased the degrees of latitude towards each pole in proportion to the lengthenings of the parallels with reference to the equator." The resulting variation of the latitude scale is shown on the meridian at 350°E of his map. Later, Edward Wright and others showed how this statement of Mercator could be turned into a precise mathematical problem whose solution permitted the calculation of the latitude scale, but their methods had not been developed at the time of Mercator.Monmonier, Chapter 5 and notes at page 191. All these methods hinge on the observation that the circumference of a parallel of latitude is proportional to the cosine of the latitude, which is unity at the equator and zero at the poles. The length of a parallel, and hence the spacing of the parallels, must therefore be increased by a factor equal to the reciprocal of the cosine (i.e. the secant) of the latitude.
Mercator left no explanation of his own methods but, as long ago as 1541, he had demonstrated that he understood how to draw rhumb lines on a globe.The curved rhumb lines on the terrestrial globe of 1541 are clearly visible. Images of the copy of the Globe in the British Maritime Museum may be found in Globes at Greenwich by Elly Dekker.