Do all maps need a legend?

Legends play a role in understanding how a topic is visually represented in the map. Cartographic theory tells us the map reader starts with the title. This is the so called external identification step, and informs about the topic of the map. In a second step the reader will look at the legend. This is the internal identification and informs about how the topic is represented. The ’final’ step is actual reading of the map content. However, maps on screens often lack a legend leaving the reader in doubt on how to interpret the content. The main reason is that the screens are small, or that multiple views are shown on the same desktop screen. Some application allow one to activatie a legend window or by hovering a pointer like a mouse over the symbols might reveal information. What if the map is more intuitively designed such that a separate legend is not required? Maybe it is possible to integrate the legend information in the external identification step or in the actual map reading. This last idea is not new. The New York Times has often used annotations to explain the meaning of symbols found in their maps. Annotations can not only explain meaning, they could also supplement the map with additional information. And maybe it is also possible to add such information into the title. Many question remain: would these approaches work for all map types? How do these maps perform compared to traditionally structured maps?