Dynamic and Interactive Displays

The term dynamic display is applied to displays capable of change, in contrast to static displays, such as paper maps and graphics. Changes in a dynamic display may occur in an automatic manner or in response to actions of the user. The term interactive display is applied to dynamic displays that change in response to a user's actions. Dynamic displays capable of changing automatically are often called animated displays. An animated display may at the same time be interactive. At the very least, the user may interactively stop, resume, and restart the play, but more advanced interaction possibilities may also be provided.

Computer animation is often used in a straightforward way to display dynamic phenomena. In particular, dynamic phenomena related to geographic space are most often visualized by means of animated maps. Many examples of such maps may be found on the Web. Thus, animated maps depicting various topics of American history are available at http://AnimatedAtlas.com. The Web site of the National Atlas of the United States contains animated maps portraying the spread of invasive species during a range of years and the progression of vegetation growth during a year.

Another frequently encountered class of animated displays is fly-through displays, which present various objects or geographical areas as they appear from different viewpoints. Typically, fly-through displays allow very little or no interactivity. Animation may also be used to present large and/or complex content by portions. For example, different themes may alternate in an animated map of a geographic area: terrain, rivers and lakes, landmarks, vegetation, administrative boundaries, roads, and so on.

Interactive displays and, in particular, maps and virtual globes are nowadays frequently encountered on the Web. Well-known among these are Google Maps and Google Earth, online mapping and route planning services such as Map24, and maps displaying election results (e.g., those at http://NYTimes.com). Typically, interactive maps and globes (as well as other types of display representing large amounts of data and complex data) provide facilities for view navigation. The most basic navigation tools are zooming and panning. Perspective views of three-dimensional objects or spaces provide tools for controlling the user's viewpoint in the scene. Visualization researchers suggest “intelligent” navigation techniques that adjust the view to the user's focus of interest so that the visual prominence (in particular, size of graphical elements) and level of shown detail vary depending on the relevance of the information in different parts of the display for the user.

Another typical feature of interactive displays is providing additional information about objects or places in response to clicking on graphical elements representing these objects or places. The information may be shown in a pop-up window that appears near the cursor position, in a dedicated area of the display or in an adjacent subwindow.

Thematic maps, such as tourist maps and maps of election results, often support more advanced interaction, allowing the user to alter the information content of the display or the representation of the information. Examples of such interaction include the following:

• Selecting information layers (e.g., accommodation, museums, restaurants, bar/nightlife) on a tourist map or toggling the visibility of the layers
• Selecting time moments or intervals in displays of time-related information
• Changing the spatial scale (e.g., states or counties)
• Changing the theme (e.g., president elections or governor elections, absolute values or differences in comparison with the previous time)
• Choosing the visualization method (e.g., choropleth map or proportional symbols)

Interactive displays used for specialized services may be supplied with specific interaction facilities, such as selection of source, destination, and intermediate places in route planning.

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