- Figure-ground in map design
An effectively designed
mapis one in which the intended message is clearly communicated to the map user. By employing the concept of figure-ground, a viewer can easily distinguish between the main figure on a map and the background information. Several concepts that are key to developing good figure-ground in any cartographic design are differentiation, closed form, centrality, articulation and good contour. In addition, by considering the intended intellectual hierarchy, or the order of importance of each map element, the author can develop a visual hierarchy on the map that corresponds appropriately.
Figure-ground cartographic elements
Differentiation is described as the ability to easily discriminate the main figure from the ground. This can be accomplished by designing the desired figure as visually heterogeneous and reducing the level of distraction caused by the ground. By adding surface patterns or textures to the figure, visual differentiation will lead to figure definition [Borden D. Dent, 1972, "Visual organization and thematic map design", "Annals of the Association for American Geographers", p. 79-93.] .
Incorporation of closure on a map is important because percipients interpret the figure to be the object or objects in the map that are closed [Arthur Robinson et al., Elements of Cartography, 1995] . Additionally, there is a tendency for the percipient to complete or close unfinished objects. The location and shape of central figures on a map can be adjusted by varying the scale, projection, and format [Dent, ibid] .
The figure of emphasis should be centrally located and surrounded by areas of a different character with contrast that lessens ground importance visually and emphasized the main figure. Both alignment and centering can be achieved through measurement or through visual approximation [Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, and Hugh H. Howard, 2005, "Thematic Cartography and Geographic Visualization", 2nd ed., Pearson Prentice Hall, Upper Saddle River, NJ] . The concept of centrality is important because the object located in the center of a map is most often assumed to be the figure. Other map elements can be centered in the remaining visual space after the figure has been centered.
Articulation utilizes texture to differentiate figure from ground. One common example of using articulation on a map is differentiating a
continentfrom the ocean. The ocean, in most cases, will be the ground and the continent will be the figure [Dent, ibid] . By adding fine-textured shading to water, the continent pops out visually as the figure [G. Head, 1972, "Land-water differentiation in black and white cartography", "The Canadian Cartographer", vol. 9, no. 1, p. 25-38.] . Another method that can be employed for articulation called is vignetting, or the inclusion of brightness gradients at the land-water edge.
Good contour on the map can be described as the viewer’s ability to continue the line throughout the map. The figure is formed by a contour or outline (as opposed to an isometric
contour line), the common boundary between the figure and ground, usually through a brightness contrast [A.M. MacEachren and T.A. Mistrick, "The role of brightness differences in figure-ground: is darker figure?", "The Cartographic Journal", 29:91-100, December 1992.] . If a figure is not separated entirely from the ground, a simple black contour line can be drawn around the figure enclosing it and thus differentiating it from the ground [Dent, ibid] .
Intellectual hierarchy, also known as a scale of concepts [Mark Monmonier, 1993, "Mapping it Out: Expository Cartography for the Humanities and Social Sciences", University of Chicago Press, Chicago, IL.] , refers to the idea that some map features are more important than others. The placement on a map or the ordering of information will convey relative importance of map features to the percipient. If developed on the map correctly, the intellectual hierarchy will correspond to the visual hierarchy established on the map. By developing a visual hierarchy, the percipient can distinguish relative importance to map objects, drawing attention to the most important objects first. By emphasizing the colors of important figures and fading out the colors on less important figures, the perceived distance between the two is increased. Also by employing color contrasts, contour sharpness can be adjusted [Dent, ibid] .
Research in figure-ground relationships
Fields other than cartography, such as
psychology, neurology, and computer science, have studied differentiation of figure from ground. Many studies have employed different experiments, varying the shades, textures, and orientations of test pictures to determine the best method for figure-ground design with mixed results. A current application of figure-ground research is the development of computer visionfor robots. By studying the way humans perceive figure and ground, methods can be developed to improve computer programmed machine vision [Peter Nordlund, 1998, "Figure-ground segmentation using multiple cues", Doctoral Dissertation, Department of Numerical Science and Computing Science, Stockholm University, Stockholm, Sweden.] .
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