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Culture and history · How ideas travel

The Piri Reis map and map projections

Drawn on gazelle skin at Gallipoli in 1513, the Piri Reis map was compiled from about twenty sources, including a lost map by Columbus. Explore the compass lines of portolan charts, why flattening a globe always distorts something, and why the "ice-free Antarctica" legend falls apart.

  • 18 min
  • 2 simulations
  • Mini quiz

Updated:

Preview

The question

Peel an orange and try to lay the peel out perfectly flat on the table, without tearing or crumpling it. You can't: the peel either tears or stretches somewhere. This is exactly the problem mapmakers have wrestled with for centuries. Now think about this too: in 1929, at Topkapi Palace in Istanbul, researchers going through the library's holdings come across a map drawn in 1513. The map tries to fit coasts that explorers had only just seen, older sources and a lost map by Columbus onto a single skin. How accurate can the result be?

Try it yourself

No account needed: change the values and check your answer. Some simulations ask for a prediction before they start; it doesn't matter whether it's right or wrong.

Number line

How many kilometres in a degree of latitude?

Drag the marker, or move it in steps of 1 km with the arrow keys, then press Check.

Prediction

Predict first

Which of these do you think is closest to the length of one degree of latitude?

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Matching

Documented or legend?

Choose a category for each claim, then press Check.

Prediction

Predict first

How can you best tell that a piece of information about a map is "documented"?

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Frequently asked

5 questions

Does the Piri Reis map show Antarctica without ice?

No. Antarctica was first sighted in 1820, and the continent has been under ice for millions of years; no human ever saw that coast ice-free. The bend in the south of the map fits a distortion common in compiled maps, and the map's own note on that region says these lands are very hot and that large snakes are said to live there.

Is the Piri Reis map the first map to show the Americas?

No. Juan de la Cosa's map of 1500 and the Waldseemüller map of 1507 are older. Piri Reis's 1513 map is one of the oldest maps to show the Americas.

Where did Piri Reis get his information?

In the notes on the map he writes that he compiled it from about 20 sources: maps thought to come from the Ptolemaic tradition, an Arab map, four Portuguese maps and a map by Columbus. Since none of Columbus's own maps survive, this note is very valuable.

Why are there no lines of latitude and longitude on the map?

Because it is a portolan chart. Instead of a latitude–longitude grid, these maps have wind roses and compass lines spreading in every direction, and sailors read the course between two ports from them. Also, a reliable clock for finding longitude at sea was only built in the 18th century.

Is the Mercator map wrong?

It is not wrong; it was chosen for a purpose. No flat map can show angles, areas and distances correctly all at once. Mercator preserves angles, which makes it useful for navigation, but it enlarges areas near the poles: Greenland looks close to Africa in size, even though it is about 14 times smaller.