How Accurate Were Renaissance Maps?
The maps produced in Europe during the Renaissance, roughly 1400 to 1600, varied enormously in their accuracy. Some were remarkably good, especially the portolan charts of the Mediterranean and the coastlines of Western Europe. Others were full of errors, particularly in their depiction of the interiors of continents, the polar regions, and the Pacific Ocean. The accuracy of any given map depended on the cartographer’s sources, the state of geographic knowledge at the time, and the cartographer’s skill in reconciling conflicting information. To see how these maps compared with earlier world maps, see our page on who made the first accurate world maps. For a broader treatment of Renaissance cartography, see our cluster on cartography and maps in the Age of Exploration.
The standard scholarly treatment is J.B. Harley and David Woodward’s History of Cartography (1987– , six volumes in progress), and Matthew Edney’s Cartography: The Ideal and Its History (2019) provides the best short account of what the early modern map actually was. Norman Thrower’s Maps and Civilization (3rd ed., 2008) is the standard textbook. The argument of this page: Renaissance maps were accurate in different ways at different times, and a single “accuracy” number is a category mistake. The right question is, accurate for what purpose, and based on what evidence?
What Renaissance Maps Got Right
Renaissance maps were often remarkably accurate in the regions that European cartographers knew best: the Mediterranean basin, the Atlantic coast of Europe, and the African coast as far as the equator. The portolan charts of the fourteenth and fifteenth centuries, which were the working charts of pilots, depicted coastlines precisely, often to within a few nautical miles of modern positions. The great world maps of the sixteenth century, from the Cantino Planisphere of 1502 to Mercator’s world map of 1569, were generally accurate in the latitudes of major places, and they correctly showed the overall arrangement of continents and oceans. For coastal navigation, Renaissance maps were often good enough to be used well into the eighteenth century, and many were incorporated into the great hydrographic surveys of the nineteenth century.
Latitude
Latitude was generally well-measured in the Age of Exploration, because it could be determined by astronomical observation using the mariner’s astrolabe, the cross-staff, or the backstaff. A skilled navigator in the sixteenth century could determine his latitude to within half a degree or better, and the latitudes of major places on Renaissance maps were usually within a degree or two of their true values. Columbus, for example, was famously off in his estimate of his longitude on his first voyage, but his latitudes were generally accurate to within a degree. The accuracy of latitude measurements was one of the foundations of latitude sailing, a technique that allowed navigators to find their way to a known destination without knowing their longitude.
What Renaissance Maps Got Wrong
Renaissance maps were much less accurate in three areas: longitude, the interiors of continents, and the Pacific Ocean.
Longitude
Longitude was the great unsolved problem of Renaissance navigation. Without an accurate method of determining longitude, no navigator could know his east-west position with any precision, and the longitudes of places on Renaissance maps were often wildly off. The classic example is the size of the Mediterranean Sea, which on many sixteenth-century maps shows as much longer in the east-west direction than it actually is — a distortion caused by cumulative errors in longitude measurement. Columbus, who used the latitude of Lisbon as the prime meridian, placed the longitude of the Bahamas much further west than they actually are. The longitude problem was not solved until the eighteenth century, with the development of the marine chronometer by John Harrison.
Interiors of Continents
The interiors of continents were largely unknown to European cartographers in the Renaissance, and the maps of the period were often filled with imaginary mountains, rivers, and kingdoms. The interior of Africa, in particular, was a great blank on most sixteenth-century maps, and the myths of a great Christian kingdom in the African interior, of a vast river system, and of a southern African continent were common. The interior of North America was similarly unknown, and the early maps of the continent showed a strange mixture of Spanish, French, and English reports. The interior of South America was better known in some respects, especially after the Spanish conquest of the Inca Empire, but even there the maps were often distorted by conflicting information. The geography of the interior of Asia was the best known, drawing on the reports of missionaries and merchants, but even there the maps were full of errors.
The Pacific Ocean
The Pacific Ocean was the last great region to be mapped, and Renaissance maps of the Pacific were particularly inaccurate. The first European to cross the Pacific was Ferdinand Magellan in 1520–1521, and the size and shape of the ocean were not known with any precision until the eighteenth century. The early maps showed a much smaller Pacific than the actual ocean, often depicting Asia as not far west of the Americas. The famous Waldseemüller map of 1507 showed a narrow ocean separating the Americas from Asia, and many subsequent maps perpetuated the error. For the context of these voyages, see our page on Ferdinand Magellan and the first circumnavigation.
Famous Errors on Renaissance Maps
Several famous errors recur on Renaissance maps. Ptolemy’s error of underestimating the circumference of the Earth was transmitted to fifteenth-century cartographers and contributed to Columbus’s miscalculation of the distance to Asia. The great southern continent of Terra Australis — a hypothetical landmass in the southern hemisphere — appeared on most sixteenth-century maps, reflecting both classical theory and the hope that there was a large, habitable southern continent. The Northwest Passage and the Northeast Passage — imagined sea routes around the top of North America and Eurasia — were sought for centuries and were the focus of many expeditions. The Sea of the West and the Strait of Anian, imaginary bodies of water in the interior of North America, appeared on many seventeenth- and eighteenth-century maps. None of these features existed, and the errors persisted for centuries, only gradually being corrected as explorers and cartographers gathered more accurate information.
The Improvement of Map Accuracy Over Time
The accuracy of Renaissance maps improved steadily over the fifteenth, sixteenth, and seventeenth centuries, as the voyages of exploration added new information and as the printing press let disseminate updated maps widely. The great world maps of the sixteenth century — the Cantino Planisphere of 1502, the Waldseemüller map of 1507, Mercator’s world map of 1569 — represented a significant advance over the maps of the fifteenth century, and the Dutch cartography of the seventeenth century, exemplified by the Blaeu and Hondius atlases, was even more accurate. By the late seventeenth century, the coastlines of the major continents were generally well-mapped, and the principal remaining error was in longitude. The eighteenth-century voyages of James Cook and others, combined with the development of the marine chronometer, finally brought map accuracy to a level comparable to modern hydrographic surveys. The relationship between these improvements and the broader story of the era is treated in our ships, navigation, and technology pillar.
How to Judge the Accuracy of a Renaissance Map
To judge the accuracy of any given Renaissance map, three questions are worth asking. First, what is the source of the geographic information on the map? Maps based on the reports of pilots, explorers, and hydrographers were generally more accurate than maps based on classical texts or the speculation of armchair geographers. Second, what is the date of the map, and what voyages had been completed by that time? Maps made after the great voyages of the sixteenth century (Magellan, Drake, Cavendish) are generally more accurate than maps made before. Third, what is the purpose of the map? Maps intended for navigation were typically more accurate than maps intended for symbolic or decorative purposes, and maps of well-known regions (the Mediterranean, the Atlantic coast) were typically more accurate than maps of remote regions. The best Renaissance maps are remarkable works of science; the worst are imaginative fantasies. The truth of a Renaissance map lies in its sources, and the story of its accuracy is the story of the gradual accumulation of geographic knowledge in early modern Europe.