God’s Portolan

God gave us a map that leads away from danger and guides us toward eternal life.

Sailing ships on the Mediterranean Sea in the Middle Ages had no radios. No binoculars. And no GPS devices.

So, what was a navigator to do? Use a portolan chart.

Hand-drawn and often quite colorful, these charts were written on vellum, an animal skin that had been prepared by cleaning, bleaching and stretching. The charts contained information that was lifesaving for sailors, who used them to find their way to the safety of a port. Although they contained very little information about inland geography, the charts provided crucial data about coastlines and harbors.

Sailors called them “portolans,” from the Italian word portolano, meaning “harbor official” or “navigation manual.”

Portolans were used for more than 500 years, showing seafarers where to dock and how to avoid danger. According to the Yale Alumni Magazine, they were “renowned for their accuracy — which is remarkable, as early cartographers couldn’t see the coast from...