Cartographic historian Chet Van Duzer discusses early modern maps and the methods used by map makers to indicate certainty and uncertainty about the accuracy of their maps at the National Library of Australia.

We tend to trust maps as accurate depictions of the world, and most early modern cartographers are content to benefit from that trust without raising questions about the reliability of their sources. Chet Van Duzer examines several methods that cartographers used from the fifteenth to the eighteenth centuries to depart from this convention and indicate to their viewers which parts of their map they were certain about, and which they were uncertain about.

Some of these methods include listing sites about whose location the cartographer is uncertain, using a different graphic style to depict unknown coastlines, using signs to distinguish between certain and uncertain regions, and surrendering to uncertainty and reprinting varying maps of the same region together.