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. This is one of the few factors in which figure-ground and visual hierarchy have opposite effect. Interposition is when some features appear to be "in front" of others in the visual field, with the former partially obscuring the latter. The former thus has a stronger recognition as a figure. This property could be considered a more complex use of closure. Articulation utilizes texture to differentiate figure from ground. One common example of using articulation on a map is differentiating a continent from the ocean. The ocean, in most cases, will be the ground and the continent will be the figure. By adding fine-textured shading to water, the continent pops out visually as the figure. 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 Cartography