An Exclusive Directions Magazine Series
Readers of this magazine are unlikely to need convincing about the inherent utility of maps. As representations of information, maps enable the analysis of spatial distributions and patterns and are a medium for communication both for and by the mapmaker. In fact, a map is a common metaphor for the arrangement of any type of information because being able to visualize spatial relationships among the data, whether words, numbers, shapes, images, objects, or concepts, helps us interpret and extract meaning.
GIS was designed for mapping geographic space, though a printed map is only one of many GIS products. I remind my students to postpone printing of their layout designs as long as possible, knowing that once hard copy is produced, the connection with the life-giving database is severed. In fields with a long history of, and expectation for, printed maps, such as the geological sciences, there are calls for greater acceptance of data sharing in alternative formats, given the time commitment involved to design, produce and distribute paper products. With improvements in the interoperability of applications and the increased emphasis on web mapping, we can expect fewer projects to yield printed maps in the future.
But regardless of their format, maps remain essential to the process of making decisions, explaining situations, displaying spatial analyses and establishing a setting. This month we begin a series of articles on Communicating through Maps, intended to highlight some of the most salient aspects of map design and usage within a modern GIS context. Contributing authors will share their ideas on topics such as representing uncertainty and best practices for communicating via web-based maps, among others. In this article, we begin with some general principles and ideas.
How well a map communicates information to its audience is in large part a function of cartographic design, yet formal training in cartography isn’t very common in a modern education, nor is it required in GIS degree or certificate programs. Companies such as CartoDB and Stamen have prioritized cartographically-informed design options into their user experience. Esri’s Mapping Center provides a great breadth of support and resources, and their annually produced Map Book exemplifies marvelous productions. Plenty of opportunities exist for expert advice and guidance — see the References and Resources section for a few options — but in the end it’s up to the individual mapmaker to produce an effective map or not. Effectiveness is measured by whatever the purpose of the map and the intent of the mapmaker are, but for the sake of this discussion, it’s about how well a map helps to communicate a message. Communication is a two-way street, and mapmakers have little or no control over many variables. First impressions are potent.
To begin, cognitive processes kick in to action the moment someone visually perceives a map. Visual image processing by the human brain is a rich and multi-step experience. Humans have a natural tendency to decode what they see and seek order out of noise. Shapes and objects may be perceived as a whole image or as individual items or differentiated as figure and ground, as described with Gestalt principles. Color-blind individuals may fail to distinguish hues and shades. Moreover, the role of prior knowledge in map interpretation is complex. The map itself is information newly being considered, but what knowledge does the viewer already have about the map’s area, content and context? What prior knowledge do they have about map reading processes overall? How can you design for experts and novices, when everyone brings different degrees and sources of expertise to the table?
Accept or doubt? Critique or regard with reservation?
As graphic representations, maps carry a certain gravitas that other images do not. So many examples of manipulated images cross our computer screens that “photoshopped” is a bona fide dictionary entry — although Adobe® prefers “manipulated with Adobe® Photoshop® software.” Of course, published maps are also deliberately altered for military, political, advertising and privacy purposes, among many other reasons, but the public is largely unaware and unassuming of these matters. Acceptance and trust are much more common reactions to a map. Even with the expansion of Do-It-Yourself web mapping sites, so few people in the world have ever made a map with modern digital technologies that they have no idea how easy it is to rearrange or misrepresent information.
People are also unfamiliar with the sources of geographic information on a map and how they’re derived. Our early experiences with printed maps are most likely to be with a government production, such as a topographic map from the U.S. Geological Survey, or a road map with its authoritative lines and standardized symbols. As a child, I for one certainly assumed that they must have been provided by a trustworthy and informed source, whatever that might have been. Blindly trusting satellite navigation maps is one all-too-common example of being misguided.
Map legends ought to be the map to a map. An effective legend is the guiding light to interpreting a map’s symbols and patterns, but even supremely well-designed legends may not get the consideration and close reading they merit. Maybe the map is being used in a crisis situation and the viewer has no time for methodical interpretation. More often, it’s our dislike of reading instructions and user manuals, and our increasingly short attention spans that cause our oversight. Manipulating the symbology of choropleth maps is a frequent activity in an introductory GIS course, designed to illustrate how different classification schemes modify the resulting map. But, again, only a tiny fraction of map readers have ever undertaken such an activity. Even if they take the time to systematically compare colors on the map to categories on the legend, they are more likely to remember their general first impression of where the light and dark colors are, ignoring the breakpoints between classification bins.
Visual plus spatial plus geospatial
Maps are undeniably an influential media for visual communication. Interestingly, the term “visual” is applied in a somewhat misleading way in education and communication. When someone says, “I’m a visual learner,” they are often referring to their preferences for images and graphics over text. But in fact all people, apart from those with visual impairments, are visual learners. Our eyesight is by far our greatest source of information, significantly more than our senses of hearing, touch, smell and taste, combined. “A picture is worth a thousand words” can be interpreted as a preference for an image over words, but the notion of worth also has to do with how effectively and rapidly meaning can be extracted, such as absorbing the gist of a scene or image.
Map reading also involves discerning the spatial relationships among mapped features. The spatial notions of distance, proximity and overlay contribute to dozens of analytical tools in a GIS. Observing patterns that are uniform, clustered or random leads to insights for understanding processes. Here, appreciating map scale is essential, and this is where GIS both complicates and facilitates map reading, by readily allowing zooming in and out, beyond or below optimal map scale levels. Spatial thinking is also required to envision dynamic movement or change, and animation can aid or hinder in explaining such processes. Communicating temporal variability presents a whole other suite of digital decision choices — something that will be discussed more in another article in this series.
So communicating through maps is both a highly visual and spatial experience, and a geospatial one as well. GIS-based mapping enables the visualization of geographic relationships that literally cannot be seen otherwise, such as in hazard risk model results, or point-source effluence and concentrations of ground water pollution, or viewsheds that would have been perceived by historical military leaders. Maps are generalized abstractions of reality, but they are still uniquely capable of serving as an effective proxy for direct experiences in distant or inaccessible portions of the world.
Our exclusive series, Communicating with Maps: