The 1491 Martellus map has long been hailed as one of the most detailed and influential depictions of the known world at that time, yet the writing on the historical gem had faded over the centuries and was largely undecipherable.
That changed when researchers announced in June they had used a multispectral imaging technique to analyze the 4-by-6½-foot map, which likely influenced Christopher Columbus’ understanding of world geography. The team divided the large map into 55 overlapping tiles and imaged each one with 12 different light frequencies, ranging from ultraviolet to infrared. Each frequency revealed slightly different details, and for the first time, historians could see Henricus Martellus’ descriptions of regions and peoples. They also confirmed that his text had been borrowed in 1507 by another wellknown German cartographer, Martin Waldseemüller.
Now plans are underway to use the imaging technique to decrypt other relics, including the Fra Mauro world map from 1455 and the earliest surviving globe from 1492, says Chet Van Duzer, the map historian who led the Martellus project. The technique is also illuminating ancient documents like the Dead Sea Scrolls and manuscripts known as palimpsests, in which the original writing was scraped off so the parchment could be reused. For scholars like Van Duzer, the technology is akin to wearing a pair of glasses that allow them to peer back in time — and the view of history keeps getting clearer.