Defined as a graphic art that occurs in time, animation is a dynamic visual statement that evolves through various interval changes in the display. Early examples of cartographic animation on film and video could not be easily duplicated, transported, or displayed, thus severely limiting their distribution and use. As a result, the making of these early animations was time-consuming and expensive. Computer technology, particularly storage devices such as the CD-ROM and advanced forms of data communications such as the World Wide Web, spurred new interest in this method of mapping during the 1990s. However, animation is still not widely used in cartography, has not been integrated in software for Geographic Information Systems (GIS), and faces a number of conceptual and methodological hurdles.