To avoid hiding critical information in a fog of detail, the map must offer a selective, incomplete view of reality. There's no escape from the cartographic paradox: to present a useful and truthful picture, an accurate map must tell white lies (p. 1).When Monmonier asserts that all maps lie, he refers to a map's need to simplify, falsify, or conceal the realities of a 3-D world in a 2-D map. However, the lies that maps tell can range from these forgivable and necessary "white lies" to more serious lies, which often go undetected, and belie the agenda of the mapmakers. Below are a few samples of these "lies" that maps tell, and how we can look at maps with a critical eye.
Necessary DistortionsOne of the most fundamental questions in mapmaking is: how does one flatten a globe onto a 2-D surface? Map projections, which accomplish this task, inevitably distort some spatial properties, and must be chosen based on the property that the mapmaker wishes to preserve, which reflects the map's ultimate function. The Mercator Projection, for example, is the most useful for navigators because it depicts accurate distance between two points on a map, but it does not preserve area, which leads to distorted country sizes (See Peters v. Mercator article).
There are also many ways in which geographic features (areas, lines, and points) are distorted. These distortions reflect a map's function and also its scale. Maps covering small areas can include more realistic details, but maps that cover larger geographic areas include less detail by necessity. Small-scale maps are still subject to a mapmaker's preferences; a mapmaker may embellish a river or a stream, for example, with many more curves and bends in order to give it a more dramatic appearance. Conversely, if a map is covering a large area, mapmakers may smooth out curves along a road to allow for clarity and legibility. They may also omit roads or other details if they clutter the map, or are not relevant to its purpose. Some cities are not included in many maps, often due to their size, but sometimes based on other characteristics. Baltimore, Maryland, USA, for example, is often omitted from maps of the United States not because of its size but because of space constraints and cluttering.
Transit Maps: Subways (and other transit lines) often use maps that distort geographic attributes such as distance or shape, in order to accomplish the task of telling someone how to get from Point A to Point B as clearly as possible. Subway lines, for instance, are often not as straight or angular as they appear on a map, but this design aids the readability of the map. Additionally, many other geographic features (natural sites, place markers, etc.) are omitted so that the transit lines are the primary focus. This map, therefore, may be spatially misleading, but manipulates and omits details in order to be useful to a viewer; in this way, function dictates form.
Other Map ManipulationsThe above examples show that all maps by necessity change, simplify, or omit some material. But how and why are some editorial decisions made? There is a fine line between emphasizing certain details, and purposefully exaggerating others. Sometimes, a mapmaker's decisions can lead to a map with misleading information that reveals a particular agenda. This is apparent in the case of maps used for advertisement purposes. A map's elements can be strategically used, and certain details can be omitted in order to depict a product or service in a positive light.
Maps have also frequently been used as political tools. As Robert Edsall (2007) states, "some maps…do not serve the traditional purposes of maps but, rather, exist as symbols themselves, much like corporate logos, communicating meaning and evoking emotional responses" (p. 335). Maps, in this sense, are embedded with cultural significance, often evoking feelings of national unity and power. One of the ways that this is accomplished is by the use of strong graphical representations: bold lines and text, and evocative symbols. Another key method of imbuing a map with meaning is through the strategic use of color. Color is an important aspect of map design, but can also be used to evoke strong feelings in a viewer, even subconsciously. In chloropleth maps, for example, a strategic color gradient can imply varying intensities of a phenomenon, as opposed to simply representing data.
Place Advertising: Cities, states, and countries often use maps to draw visitors to a particular place by depicting it in the best light. A coastal state, for instance, may use bright colors and attractive symbols to highlight beach areas. By accentuating the coast's attractive qualities, it attempts to entice viewers. However, other information such as roads or city-size that indicate relevant factors such accommodations or beach accessibility may be omitted, and can leave visitors misguided.
Smart Map ViewingSmart readers tend to take written facts with a grain of salt; we expect newspapers to fact check their articles, and are often wary of verbal lies. Why, then, don't we apply that critical eye to maps? If particular details are left out or exaggerated on a map, or if its color pattern is particularly emotional, we must ask ourselves: what purpose does this map serve? Monmonier warns of cartophobia, or an unhealthy skepticism of maps, but encourages smart map viewers; those that are conscious of white lies and wary of bigger ones.
Edsall, R. M. (2007). Iconic Maps in American Political Discourse. Cartographica, 42(4), 335-347. Monmonier, Mark. (1991). How to Lie with Maps. Chicago: University of Chicago Press.