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Between Reality and Abstraction:
Non-Temporal Applications of Cartographic Animation

Michael P. Peterson
Department of Geography / Geology
University of Nebraska at Omaha
Omaha, NE 68182




The animated map is a cartographic statement that occurs in time. Its interpretation is based on the human sensitivity to detect movement or change in a display. The objective of cartographic animation is to visualize a phenomenon that would not be apparent if the maps were viewed individually. Animation may be viewed as one of the defining characteristics of cartographic visualization, which may itself be viewed as a further manifestation of a general research direction in cartographic communication. A basic distinction is made in cartography between temporal and non-temporal cartographic animation. Temporal animations are limited to the display of change over time. Non-temporal cartographic animations depict changes caused by some other variable, and may include viewing temporal data in a non-temporal way, depicting different but related spatial data sets, or showing data with different levels of generalization. This latter form of animation is particularly important because it can be used to depict the cartographic process and thereby convey both a data set and the transformations that have been made for its display.

1.0 Introduction

Animation is a "graphic art that occurs in time" (Baecker and Small 1990). It is a dynamic visual statement that evolves through movement or change in the display. In cartography, the most important aspect of animation is that it depicts something that would not be evident if the maps were viewed individually. In a sense, what happens between each frame is more important than what exists on each frame (Peterson 1995, 48). In cartography, an interest in animation preceeds that of visualization. The technique is mentioned in the literature as early as 1959 (Thrower). The method was studied and used intermittantly in cartography in the three decades thereafter (Cornwell and Robinson 1966; Tobler 1970; Moellering 1972, 1973a, 1973b, 1980a, 1980b; Rase 1974). In general, cartographic animation was viewed as an interesting but not a viable technique, a fact lamented by Campbell and Egbert (1990), and Karl (1992). In practical terms cartographic animations were both difficult to create and difficult to "deliver" to a potential user. This was probably the major limitation in its use. The Internet is now providing a medium for the distribution and viewing of such animations and is spurring a renewed interest in the technique.

A considerable amount of cartographic research has examined animation since the early 1990's contributing to a conceptual foundation for its use. Monmonier (1990) proposes a scripting mechanism to direct the display of a map series. Gersmehl (1990) outlines nine metaphors of cartographic animation, Slocum, et.al., (1990) examines the sequenced display of choropleth maps, DiBiase, et.al. (1992) present a series of dynamic variables for cartographic animation, and MacEachren (1994) examines time as a cartographic variable. A major obstacle to the increased use of animation in cartography has been a lack of software tools that effectively automate the cartographic animation process. Peterson (1993) describes a computer program and associated user interface for the automated production of animations of choropleth maps. A version of the program, designed for the initial Apple Macintosh (pre 68040 processors) with a black & white display, can be downloaded through the Internet.

Visualization and the Communication Paradigm-
The increased interest in cartographic animation since the beginning of this decade was first associated with a general trend toward the integration of multimedia techniques in the display of maps and then became tied to cartographic visualization (Dorling 1992). In part, cartographic visualization was characterized as being distinct and in some ways contradictory to cartographic communication, a paradigm that has guided cartographic research, albeit in different forms, since the 1950's. In drawing a distinction between visualization and communication, MacEachren (1994, p. 7-8) makes the point that some maps are "designed primarily to facilitate transfer of knowledge from a few people to many people," while other maps are intended "to help individuals (or a small group of individuals) think spatially." A parallel connotation of this definition is that cartographic visualization is a higher level, almost elitist, form of map use.

To further distinguish between cartographic communication and cartographic visualization, the former is defined narrowly as the communication of a particular message. Indeed, if defined in this way, cartographic communication would be contradictory to the exploratory aspect of cartographic visualization - where the particular message may not be known. However, if cartographic communication is defined more broadly as improving the map as a form of data representation and communication, cartographic visualization may be viewed as another expression of the general communication paradigm.

The elitist aspect of cartographic visualization is related to the tradition of exploratory data analysis in statistics. Here, the emphasis is on the use of graphics in the development of ideas, not merely the use of graphics in their presentation (Unwin, 1994, 517). But, the distinction between analysis and presentation with any type of graphics display is a tenuous one. Map use is by definition an inquisitive and analytical process. Every map can be used for analysis, even maps on paper that are designed for 'presentation.' To argue that some forms of map use are on a higher level than others because they are a "visualization" is elitist. Efforts should instead be directed at improving all forms of map use.

The distinction between maps for presentation and maps for analysis, commonly regarded as the distinguishing characteristic of cartographic visualization, is largely an artificial one. Cartographic visualization is not a "higher form" of map use usable by only an elite "few." Rather, it is a computer-assisted form of map use that incorporates interaction and animation in the display of maps. Interaction and animation may be seen as the cornerstones of cartographic visualization. Although a cartographic animation creates a "presentation" viewable in time, it, like any other map presentation, only has meaning if it is used for analysis.

Temporal and Non-Temporal Cartographic Animation-
A major research direction in cartographic animation has been identifying the variables of animation. The basic variables have been derived from the animation literature and include such aspects as changes in the size, shape, position, speed, viewpoint, distance, scene, texture, pattern, shading, and color (Hayward 1984). Magnenat-Thalman, et.al. (1990), effectively categorize these as animation objects, graphic objects, and the camera. Animation objects may themselves be static or dynamic. Graphic objects include both geometric (size, shape, position) and graphic (texture, pattern, shading, color) characteristics. The camera is defined by distance to the graphic object, angle of orientation, and direction.

A major distinction is made in cartography between temporal and non-temporal animation. Most cartographic animations depict change over time. Examples of temporal cartographic animations would include the movement of clouds as in this animation of Hurricane Andrew (660 KB, MPEG, description), this color-enhanced GOES-8 multispectral series (347 KB, MPEG), or the diffusion of population as in this animation of the San Francisco Bay area from 1800-1990 (446 KB, MPEG, description), or the diffusion of a farming method such as irrigation, shown here for the state of Nebraska by county between 1954-1987 (264 KB, QuickTime, description).

Temporal cartographic animations have a time-lapse element. The sequence of maps have an analog relationship with time. In her recent dissertation, Dransch (1995) makes the distinction between temporal and non-temporal cartographic animation. According to Dransch, in temporal animation a change is depicted in the "geo-objects" relative to time. In non-temporal animation, there is a change in the "animation-objects" relative to factors other than time such as a change in the position of the "camera" or light source, or some other non-temporal variable. Time, however, is an aspect of every animation. For temporal cartographic animation, Dransch differentiates between "real time" (realen Zeit) which is depicted as part of a temporal animation, and "presentation time" (Präsentationszeit) which is the time used to show the animation.

One aspect of cartographic visualization is exploring methods and uses of non-temporal cartographic animation. This paper, for the first time, presents examples of the different forms of non-temporal cartographic animation, particularly, the use of animation to display varying levels of cartographic abstraction or generalization. This particular form of animation is viewed as a window to the cartographic process and a way of bridging the gap between the map and the reality it depicts. It is a form of visualization that not only helps in thinking "spatially" but "cartographically" as well because it depicts the transformations involved in making the map.

2.0 Categories of Non-Temporal Cartographic Animation

Cartographic animation may best be defined as the depiction of change in space through the presentation of a series of maps in quick succession. Temporal animations depict change through time. Non-temporal animations show change that is caused by factors other than time such as depicting the deformation caused by a map projection (Gersmehl 1990), a three-dimensional surface (Moellering 1980a, 1980b), or the classification of data (Peterson 1993). Non-temporal uses of animation in cartography are evolving into the major application of the technique.

Two general forms of non-temporal cartographic animation can be identified. In the first type, there is a change in the data that is being shown. Animations that depict a change in the data can be further categorized by animations that a) depict events that happen in time in a non-temporal way, and b) depict data that are not related in time. In the second general form of animation, there is a change in the representation of the data - usually a change in the level of abstraction or generalization. Animations that alter the representation of the data can be categorized based on the type of abstraction (selection, classificaiton, etc.) that is being animated. It is important to note that the two forms of animation can be combined in a single animation.

Changing Time
Cartographers have adapted the methods of visualization, many developed within statistics, to the display of maps and have formed a set of "dynamic variables," analogous to Bertin's (1981) graphic variables. One of these variables is called reexpression (DiBiase, et al. 1992). The term denotes an alternative graphic representation that results from a transformation of the original data. Examples of reexpression are:

The order of scenes in a time-series animation is usually from beginning to end. Reordering involves the presentation of the scenes in a different order, usually according to an attribute. DiBiase, et al. (1992) give the example of depicting earthquake events. A typical time-series animation would depict earthquake events through time. Another approach would be to order the frames by the number of deaths caused by the earthquake. In this way an emphasis is placed on a measure of earthquake severity.

Pacing refers to varying the duration of scenes. Once again, using the earthquake example, DiBiase, et al. (1992) propose that the duration of the scene be proportional to the magnitude of the earthquake or the number of deaths. The pacing of an animation is not common as users seem to prefer a more consistent change in the display.

Changing the Data
In this form of non-temporal cartographic animation, different data sets are viewed in the form of animation. The data sets are not related in time. Each map in the animation has roughly the same level of abstraction or generalization. The objective is to show a change or a trend.

The Fly-Through-
Probably the most widely used non-temporal animation in cartography is the "fly-through." Moellering (1980a, 1980b) showed how an animation could be made of a three-dimensional object by moving around it in time. The technique has been expanded by combining a digital image of the earth and an elevation model. A large number of oblique views are then constructed to simulate flying through a terrain. The method was demonstrated in LA: The Movie created by the Jet Propulsion Laboratory (JPL 1987). The example referenced here is a fly-through of the Grand Canyon (7.5 MB, QuickTime). Software for creating fly-throughs is readily available and includes: Virtus VR, KPT Bryce, Vista Pro, and Scenery Animator (address list). The fly-though is also common in weather forecasts to depict the location of clouds, as in this 3-D animation through the center of the United States (1.1 MB, QuickTime, description).

The Graphic Zoom-
Similar to the fly-through, the zoom changes the position of the map viewer relative to the objects being viewed. Like zooming into a photograph, features become larger but there is no change in the detail that is shown.

Spatial Trend-
A fly-through represents the changing trends in a physical landscape. A spatial trend can also be evident when examining a series of related variables of population characteristics. For example, the percentage of population in age groups (5-13, 19-24, 45-54 years of age) will usually show a clear regionalization in a city, particularly in North America, with the older populations closer to the center and younger populations nearer the periphery. In this animation of age groups (664 KB, QuickTime) for the city of Omaha, Nebraska, the difference in the population by age group can be seen as a wave moving from one side of the map to the other. The city is bounded by the Missouri river to the east. Newer parts of the city with younger populations are developing on the western side. Variables such as income and housing valuation depict similar spatial trends.

Changing the Representation of the Data
Another type of non-temporal animation depicts the changes caused by different forms or levels of data abstraction. Maps differ in their level of abstraction, normally caused by differences in scale. The abstraction of reality makes maps meaningful to us but also makes them harder to interpret. The importance of this form of animation is that it creates a link between reality and the abstraction process. By animating the process, a better "view" is created of the how the generalized map is actually constructed, creating a link between the abstraction and reality. In a sense, this form of animation creates a "window" to the abstraction process. Cartographic abstraction is typically divided into five categories - selection, simplification, exaggeration, classification, symbolization (Muehrcke & Muehrcke 1992). Each of these forms of abstraction can be the subject of an animation.

Cartographic Zoom-
On maps of different scale, a decrease in scale is accompanied by a decrease in detail. The removal of featues for the smaller scale map is called selection. The removal of detail from a line such as a coastline or a river is called simplification. A normal graphic zoom does not add extra information; it simply enlarges the display. A true cartographic zoom adds extra detail to the maps at each stage in the animation process and ultimately involves all aspects of the cartographic abstraction process. Cartographic zooms are a part of CD-ROM encyclopedias, such as that produced by Grolier (1995). Interactive street mapping systems, such as MapQuest and MapBlast implement an automatic selection of features in representing maps at different scales. One aspect of the cartographic zoom which has been a subject of research has been the scale changes that accompany the zoom (von Wyss 1996).

Classification Animation-
The effect of data classification can be observed with a classification animation. Here each frame of the animation depicts a different classification scheme. A number of different statistical and nonstatistical methods exist for classifying quantitative data (e.g., standard deviation, natural breaks; see Dent 1993). A classification animation (50 KB, QuickTime, set the loop option) depicts a variety of classification options quickly and provide a less misleading view of the data than simply relying on one map.

Generalization Animation-
A generalization cartographic animation (578 KB, QuickTime) depicts changes caused by different numbers of classes. The maps depicted in this animation change from two to seven classes and show the effect of the number of data categories on a mapped distribution. This animation depicts the percent of births to mothers under the age of 20 for the United States in 1980. The first frame in the animation is a two-class map and the last frame is a seven class map. The legend is represented as a histogram with bars indicating the number of observations in each category.

Sound is an additional and important variable in cartographic animation that can be used to accentuate both temporal and non-temporal animations. In the example presented here, sound has been added to the generalization cartographic animation presented above. The sounds progress upward with increasing number of classes. The amount of time that each map is shown is a function of the length of the tone. The example illustrates how sound can be a useful element in the display of cartographic animations.

3.0 Summary

Visualization is an attempt to better utilize the mental imaging capabilities of the human mind and the dynamic nature of human information processing. It can be argued that animation is one of the defining aspects of visualization. Cartographic animation has been divided into two general categories: temporal and non-temporal. The non-temporal category can be further divided into animations that change in the data that is being depicted and those that change the representation of the data. This latter form of cartographic animation is a valuable addition to cartography because it presents a window to the cartographic process and thereby creates a link between the transformation processes in the map and the reality it depicts.

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