Treating cartography as a formal communication system implies that we can improve map communication if we can reduce the filtering or loss of information at various points in the system where in the system should have a positive effect, and an information loss should be impossible to overcome. Most efforts to study cartographic communication have been directed to the middle stages in the system: the cartographer's transformation of selected information into the map and the initial extraction of information from the map by the user.

p. 5 - How Maps Work: Representation, Visualization, and Design (1995)