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.
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.
Objective-
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.
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:
Reordering-
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-
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.
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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