“Whenever I find myself growing grim about the mouth,” writes Ishmael in Herman Melville classic novel Moby Dick, “I take myself to sea.”

Ishmael was not the only one. For hundreds of years, ships have cut the ocean’s salty waves, ferrying Ishmaels by the million between coasts and continents. As this striking data viz shows, their wanderings, when traced, result in an astonishingly accurate map of the world.

The visualization was created by Ben Schmidt, an assistant professor of history at Boston’s Northeastern University. Schmidt, who is expert in using visualization techniques to explore the history of the 19th century, took data on over 200 years worth of ocean journeys available through the National Oceanic and Atmospheric Administration (NOAA), traced them out, and combined them into a single image.