Figure-ground (cartography)

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 vision for robots. By studying the way humans perceive figure and ground, methods can be developed to improve computer vision algorithms. Unlike some of these other applications, in which figures and grounds are discovered in a natural visual field that may or may not have this contrast, in cartography they are intentionally created by design, based on knowledge of the visual perception tendencies of map readers. Since the early days of academic cartography, there has been a recognition of the need for maps to have a conceptual structure. In The Look of Maps (1952), Arthur Robinson emphasized the need for visual contrast in making maps that are clearly organized, including the figure-ground relationship, "the visual relation of one or more components to the background on which they are seen." In 1972, Borden Dent appears to have been the first to use the principles of perceptual psychology to develop a theory of how the figure-ground relationship emerges on maps (as well as Visual hierarchy), and a set of guidelines for design to strengthen it. MacEachren discussed the concept of visual levels as "related," but not equal, to figure-ground contrast. ==Influences on figure–ground contrast==

Several visual patterns are believed to contribute to figure-ground contrast, such that features that exhibit these patterns are easier to recognize as figures. These have been largely adopted from Gestalt psychology. • Differentiation or heterogeneity, the amount of difference in appearance between the intended figure and the intended ground. A strong figure looks significantly different than everything in the ground, while the elements of the ground look relatively similar to each other. This can be accomplished using almost any of the visual variables, such as color, size, and texture. Achieving difference is more important than using prescribed design techniques on the figure and ground; for example, a dark figure stands out on a light background just as much as a light figure stands out on a dark background. A figure with closure stands out because it looks like "a thing." The proclivity for closed objects is so strong in human visual processing that humans will perceive closure even when figures are only mostly closed. 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. • Size, in which smaller elements are more easily recognized as figures than those that fill the visual field. Another method that can be employed for articulation is called vignetting, or the inclusion of brightness gradients at the land-water edge. • Contour is the strength of the boundary or edge of a figure. 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. 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. ==Relationship to visual hierarchy==

The concept of figure-ground contrast is often confused with the concept of visual hierarchy. Both are related elements of map composition, the same design techniques frequently achieve both goals simultaneously, and they are synergistic in that strengthening one typically has the side effect of strengthening the other. The primary difference is in intent. Figure-ground contrast is about making each feature appear distinct from the rest of the features in the map, while visual hierarchy is about making each feature appear more or less important than the rest of the features in the map. == References ==