Maps are familiar objects that need little introduction. By strict definition, a map is a diagrammatic representation of the spatial environment – for example, the Earth's surface, the stars or parts thereof. The techniques of map-making, or cartography, are basically concerned with reducing the spatial characteristics of large surface areas to a form that makes them observable. Cartography has been considered as both a science and an art. As an art form and craft tradition with printed maps, cartography traditionally has sought to address aesthetic criteria for human appreciation and visual attractiveness, in addition to considerations of functional utility.