Passage IV

The Best Map of the World in the World

[A] More fictional than factual, most maps made in medieval Europe combined a smattering of accurate information with a slew of inaccurate information, guesses, and outright inventions. [B] In 1139, however, when King Roger II of Sicily wanted a new map of the known world, since he desired accuracy foremost. [C] To that end, he engaged Moroccan-born scholar Muhammad al-Idrisi. [D] Al-Idrisi adopted a systematic approach to the project, combining comparative analysis, eyewitness accounts, and scientific measurements.

Al-Idrisi had been educated in Córdoba, Spain. He also scrutinized accounts written by long-distance travelers. By comparing sources, al-Idrisi could judge their accuracy. If multiple sources agreed on things—the route of a river, for instance—it was likely true. If sources disagreed, likewise, al-Idrisi sought the truth, he dispatched a research expedition to the area in question.

Al-Idrisi brought a similarly logical approach for the positioning to locations on his map. Most mapmakers at the time arranged cities, mountains, and other features, on their maps quite haphazardly. But al-Idrisi, informed by the work of the best Arab and Greek scientists, lay out the sites on his map using astronomical coordinates.

After fifteen years of the daily grind, al-Idrisi completed his project. The final products included: a two-meter-wide silver disk engraved with a world map, an atlas containing seventy detailed regional maps, and a lengthy descriptive text. The maps were of a quality and accuracy unparalleled at the time. They noted the source of the Nile River— in Africa’s equatorial highlands—and used a sophisticated method of depicting the earth’s round shape on a flat map. Unfortunately, the maps never circulated widely. Moreover, the text wasn’t translated from Arabic for hundreds of years. It would be the twentieth century before al-Idrisi’s work received the appreciation it deserved.