GEOG 486
Cartography and Visualization

Part II: Visual Communication


In the last section we reviewed different kinds of maps. But is making maps the only purpose of cartography? In this section and the next we will discuss two different uses for cartography. In this section we discuss the more-often-thought-of purpose, that of using cartography to visually communicate data. In the next section we will discuss engaging in the process of cartography with the primary purpose of visually thinking, without the goal of creating an end-product that visually communicates data to others.

In 1952, with his slender but influential volume "The Look of Maps," Arthur Robinson called for a more objective, scientific approach to creating maps. In the final paragraph of a chapter entitled "The Cartographic Technique," he outlines his book's goal: "If we then make the obvious assumption that the content of a map is appropriate to its purpose, there yet remains the equally significant evaluation of the visual methods employed to convey that content" (p. 17, my emphasis). What Robinson implies with this statement is that a map's primary function is to communicate information to the map reader, and that we as cartographers should try to develop design principles that will make this communication a more effective and efficient process.

Responding both to Robinson's call for empirical research and the broader academic trend towards a scientific (i.e. positivist) approach to the social sciences, cartographers began to describe maps as vehicles for communication. Several cartographers constructed models of how they thought this communication process functioned. Although some of the models and flows of information were quite complex, they all shared certain common elements: geographic reality, the cartographer's interpretation of that reality, the map itself and the map reader's interpretation of reality (see Figure 1.2.1). This way of thinking about cartography has come to be known as the communication paradigm, and was the dominant way of thinking about maps and map-making from the 1960s to the early 1990s.

A schematic to show a cartographic communication model
Figure 1.2.1 Generalized cartographic communication model. Starts with the Real World, then becomes the Cartogrpher's Interpretation of the world, then the map, and then it becomes the map reader's interpretation of the world.
Credit: Adrienne Gruver

Although most cartographers now think about maps in a less restrictive manner (you'll read more about this in Part III: Visual Thinking), most maps are used to visually communicate information, so the concept is not worth discarding.

Maps can communicate information to map readers because both the map-maker and the map-reader have some common, shared understanding of what the graphical marks that make up a map mean. The science that provides a conceptual framework for thinking about this shared understanding is the science of signs, or semiotics. Three semiotic terms that are used to talk about symbology are: sign-vehicle (i.e the symbol), interpretant, and referent. Figure 1.2.2 shows one cartographic example of a semiotic model. In this example, the map symbol (upper portion of the diagram) acts as the sign-vehicle, or the carrier of meaning; the map reader's conception or mental image of a tree acts as the interpretant or concept (lower left); and the actual object in the real world (lower right) acts as the referent, or object of reference.

A graphic semiotic model of a tree.
Figure 1.2.2 Semiotic model of a tree.
Credit: Adrienne Gruver

Look at the map below in Figure 1.2.3. Even if you do not read any of the words in the map you are still able to understand much of what is being communicated simply because of the shared conceptions between you and the cartographer of the data being mapped. For instance, even if you had no cartographic or geographic education, you can quickly understand that the different sized circles represent different amounts of some phenomena, proportionally. And similarly, you can understand that the orange polygons represent areas of a phenomena. This is because the cartographer matched his/her representations and visual variables to the logic of the data, e.g. he/she used the ordinal/quantitative visual variable of size to fit the quantitative characteristic of volume of oil.

World map using proportional circles for volume of oil reserves by continent
Figure 1.2.3 Map exemplifying how symbols are best chosen based on characteristics of the data
Credit: Le Figaro

We will focus on map communication through much of this course, specifically formalizing sign-vehicle-referent relationships by learning guidelines for matching symbols to objects we want to represent in our maps. (More about this in Lesson 2, in the symbolization concept gallery item.)

Recommended Readings

If you are interested in investigating this subject further, I recommend the following:

  • Robinson, A. H. (1952). The Look of Maps. Madison, WI: the University of Wisconsin Press.
  • Peirce, C. S. (1985). Logic as Semiotic: The Theory of Signs. In R.E. Innis (Ed.) Semiotics: An Introductory Anthology (4-23). Bloomington, IN: Indiana University Press.