In the previous section we discussed the use of cartography not to make maps per se, but to visually think with data. Visual thinking is – or should be – of growing importance to cartographers because of the ever-increasing numbers of interactive maps being made available on the Internet (that enable their map users to visually think). And conversely, cartography (for visual communication) should be increasing in importance to those who use GIS or other visual information displays regularly for visual analysis because the critical decisions made to display data visually (e.g. with regard to classification, representation, aggregation) are essentially cartographic decisions, and will affect any visual analysis.
Although we will revisit visual thinking from time to time throughout this course, the majority of the course from here on out discusses cartography with regard to visual communication. For instance, in this section we discuss map purpose and audience with regard to creating a map for visual communication.
If asked to make two maps, and starting with the same dataset(s), a cartographer may produce very different looking maps, depending on who they are designing the map for and how the map is going to be used. As a cartographer, an important part of your job is to understand the audience you are designing for and what types of activities the map will be used for. Knowing or establishing your audience and the map purpose before you set about creating your map will make the design process easier and more straightforward, as well as make the map more successful, easier to use, less cluttered with details that might not be necessary, and likely more attractive to the user.
What will the users of your map want to be able to do with your map? If it is a map for navigation, will they use it to navigate walking routes? Or driving routes? Will they use it to figure out where to park? Or is the emphasis on the sites within the area rather than the routes to get there? Below are three maps of Penn State's University Park campus. They each show almost the same exact extent, and contain almost the same exact data, but they look different from one another because they are designed for different purposes. The first campus map (Figure 1.4.1) is designed primarily for the identification of buildings on campus. Parking lots and roads are visible, but it would be difficult to use this map to decide where to park if you were visiting the campus. The second campus map (Figure 1.4.2) is designed specifically for parking for Penn State permit holders, and the third map (Figure 1.4.3) is designed for navigating routes to use on campus specifically at night. Take notice of what features are emphasized in each map, and also look at some of the same features (e.g. specific buildings, parking lots and/or roads) in each map and how the design of the symbols changes from one map to the next. For example, the building footprints are colored and highlighted in the first map, but grayscale in the second and third maps.
Another important thing to consider is who your audience will be. What kind of experience do they have using maps? Where will they be when they use the map? Will they have time to read details in the map? Will they be walking? Or in transit? Will they need to acquire the information quickly? Will the users be vision-impaired? Will they be young children? What is their level of expertise in the subject matter you are mapping? Knowing about the map user will help you make decisions on what information to include on the map and what level of detail to show.
We will use some example maps of Washington D.C.'s Metro System to illustrate different decisions that a cartographer might make when designing transit maps for different audiences. The first figure below (1.4.4) is a map for transit users who have time to inspect the map and who possibly want details about all aspects of public transportation within Washington D.C. Use the link below the figure to look at the PDF of the map in more detail.
Now imagine that you are a tourist riding the Metro and you are in a Metro station. You know where you are and where you want to go, but are only interested in riding the Metrorail and not the buses. You could use the above map to figure out what line to get on, where to transfer and what stop to get off, but the map below would be better suited to your needs, and would be a much quicker read than the map above.
Now imagine that you are in transit waiting for your particular Metrorail train (e.g. on a Red line platform), but you again need to consult a Metro map to figure out how many stops it will be until you get off or transfer. You could consult either of the two above maps to figure this information out, but since this is specific information (e.g. names of stops along the Red line) that people in a specific area need (e.g. at platforms along the Red line), it makes sense to provide a map with just this particular information that transit riders can read quickly and easily. The image below is an example of a map for this specific user with that specific need. Notice how the geography of the line has been removed and the map is distilled down to visually convey only the order of the stops, which is all the information that the riders using this map need.