Historically, maps have been the primary means to store and communicate spatial data. Objects and their attributes can be readily depicted, and the human eye can quickly discern patterns and anomalies in a well-designed map. Points can be shown as symbols of various kinds, depicting anything from a windmill to a church; lines can be symbolized to distinguish between major roads, minor roads, and rivers; and areas can be symbolized with color, shading, or annotation.
Maps have traditionally existed on paper, as individual sheets or bound into atlases (a term that originated with Mercator, who produced one of the first atlases in the late 16th century). The advent of digital computers has broadened the concept of a map substantially, however. Maps can now take the form of images displayed on the screens of computers or even mobile phones. They can be dynamic, showing the Earth spinning on its axis or tracking the movement of migrating birds. Their designs can now go far beyond what was traditionally possible when maps had to be drawn by hand, incorporating a far greater range of color and texture, and even integrating sound.