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Ptolemy
Ptolemy’s Geography gave readers coordinates for places and instructions for drawing the known world. Later mapmakers could redraw his world from those numbers. Comparing the maps produced from the same text shows what a system of coordinates makes possible and what happens when the underlying information is wrong.
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Muhammad al-Idrisi
Al-Idrisi assembled geographical reports for the Norman court in Sicily. The world map associated with his Book of Roger puts south at the top. Turn it around and try locating the Mediterranean, the Black Sea, and the Persian Gulf. The exercise makes a familiar convention, north at the top, feel like a choice.
More about Muhammad al-Idrisi3
Fra Mauro
Fra Mauro used nautical charts, including one by his collaborator Andrea Bianco, to compile his world map in Venice. He disagreed with Ptolemy’s depiction of the Indian Ocean as enclosed. Look for the notes around Africa: the map lets you read some of the evidence behind a claim about the shape of the world.
More about Fra Mauro4
Martin Waldseemüller
Waldseemüller’s 1507 world map used the name America in honor of Amerigo Vespucci. It grew out of a group project in Saint-Dié that drew on published accounts of Atlantic voyages. The map is worth looking at as a record of who had the means to turn travelers’ reports into names other people would use.
More about Martin Waldseemüller5
Gerardus Mercator
Mercator’s 1569 projection lets a navigator draw a constant compass course as a straight line. Look at how the spacing between parallels grows toward the poles. That change makes the chart useful for plotting a bearing and explains why land near the poles looks so large.
More about Gerardus Mercator6
Abraham Ortelius
Ortelius brought maps together in his Theatrum Orbis Terrarum and included a catalog of his sources. Read the credits alongside the maps. The book makes visible a part of mapmaking that is easy to miss on a single sheet: finding other people’s maps and getting them into a form readers can use together.
More about Abraham Ortelius7
César-François Cassini de Thury
Born
Cassini de Thury presented a map of the triangles used to measure France to Louis XV in 1744. The network gave surveyors a common framework to work from. It also shows how much coordination a national map took, even before its makers could begin to fit the local detail onto separate sheets.
More about César-François Cassini de Thury8
Tupaia (navigator)
The Ra‘iatean navigator Tupaia made a map of Pacific islands with members of the Endeavour expedition. Researchers reconstructing its drafts argue that its directions need to be read from the island a voyage begins at. It is a good map to spend time with if you want to see what changes when different ways of giving directions meet.
More about Tupaia (navigator)9
Inō Tadataka
Born
Inō Tadataka led surveys that became the basis of a detailed map of Japan. The full map appeared in 1821, after his death, through the work of his team. Look at the arrangement of its sheets to see how much walking, measurement, and assembly went into making a coastline legible at that scale.
More about Inō Tadataka10
Alexander von Humboldt
Born
Humboldt proposed connecting places with equal temperatures by drawing lines across a map. An isotherm can cross borders or bend away from a line of latitude. It makes a pattern visible that would be difficult to spot in a table of individual readings.
More about Alexander von Humboldt11
John Snow
Born
In his account of the 1854 cholera outbreak in Soho, Snow published a map marking deaths and the locations of water pumps. Charles Frederick Cheffins drew it for him. Follow the marks toward Broad Street to see how the map communicated an argument about the water supply street by street.
More about John Snow12
Florence Kelley
Born
While living at Hull-House, Kelley led a federal investigation whose local records informed the settlement’s published maps of wages and nationalities. One map lets you compare wages house by house in a small stretch of Chicago. It gives the neighborhood a level of detail that a citywide wage average would hide.
More about Florence Kelley13
Marie Tharp
Born
Tharp plotted depth soundings and turned them into diagrams of an ocean floor that ships could sample only along their tracks. The global map made with Bruce Heezen and painted by Heinrich Berann brings that terrain into view. Compare it with the sounding profiles to see where measurement ended and informed interpretation began.
More about Marie Tharp
