appear. Smoothness of animation is also a function of the rate of change. Order refers to the time sequence in which animation is played out, usually presented in chronological sequence. Alan MacEachren extended these visual variables in 1995 to include display date (time at which change is initiated), frequency (number of times identifiable forms are displayed), and synchronization (correspondence of 2 or more time series). Types Animated maps can emphasize the existence of an occurrence at a location, emphasize an attribute of an occurrence, or represent a change in the position or attributes of an occurrence. For instance, a flashing symbol may be used to draw the map-reader's attention to a particular occurrence at one location or multiple locations across the map. Maps on the weather channel use animation to emphasize the current and predicted paths of hurricanes. The use of the Internet has allowed animated maps to become interactive. The user can witness representations of changes over time, while manipulating the direction of view, the pace or the parameters of the map displayed. Animation on maps can be mainly divided into two types: temporal and non-temporal. Temporal map animation Temporal map animation shows the ongoing gradual changes over time. Temporal maps can also be termed animated timeline maps and can be a useful reference to examine the changes ongoing on each step and analyze the progression occurring gradually as time passes. There are many purposes which temporal animation might serve to depict: displaying and analyzing geographic patterns, meteorological events, climate, natural disasters, and other multivariate data. Animated mapping of history Animated mapping is extensively used in the construction of animated maps to depict historical events in a cartographic environment, particularly in the subdiscipline of Historical geographic information system. These were one of the first applications of such maps, documented in Waldo Tobler's 1970 paper. Today, such animations often show the land ownership/occupation of specific groups over time. Importance of legend in temporal maps As in the case of static maps, it would be useful if temporal maps could also be provided with proper legend. Legends for temporal maps should not only tell the time but also let users travel over time. Various manipulations such as traveling to a certain point in time, selecting focus level, etc. should be allowed to enhance user-friendliness. Using legend in the temporal map will answer important questions related to the entity's existence (if?), the