Animated timeline maps depict historical change through a chronological sequence of individual images, with a user-controlled timeline slider. This format can display historical change in either vector (point or thematic data) or raster format (such as aerial photographs).

While various types of animated timeline maps are readily available on the web, the merits of different approaches deserve more discussion. GIS applications (such as ESRI ArcGIS 9.3) allow users to export images into various formats that can be converted into animated maps:

1) Simple GIF animated loops Individual ArcGIS maps can be exported into GIF images, and can be inserted into simple GIF animated loops. However, GIF animations have no timeline or speed controls, and limited image quality.

2) Animated map movies ArcGIS 9.3 supports its own animation tool, where a series of map images and movements can be exported as an AVI or Quicktime movie. However, these large files rely on the movie player control as the timeline slider, and limit the user to viewing only the map scale designated by the creator.

3) Flash animation maps Individual ArcGIS maps can be exported into a richer image format (such as JPG or TIFF), which can be imported into Adobe Flash Professional, and animated with ActionScript controls for a timeline slider. However, Flash maps have limited ability to zoom into detailed geographic features, or to be placed on a world map.

Currently, our favored approach is the following:
4) KML/Google Earth animated timeline maps (requires free Google Earth browser plugin)

Percentage Share of Population, by town, in Hartford County, CT, 1900-2000

First, GIS map data must be converted into KML (Keyhole Markup Language format, a standard supported by the Open Geospatial Consortium), or its compressed version, KMZ. Although ArcGIS 9.3 supports export of map layers into KML, it does not yet include time-series data (such as year intervals). To include historical time variables, we use conversion software, such as the free and open-source Export to KML or the proprietary Arc2Earth scripts for ArcGIS. A free Google Earth Embed KML gadget allows non-programmers to easily embed the appropriate code directly into the website, so that browsers with the free Google Earth plug-in can interact with animated time-series maps.

For historians, this approach to animated timeline maps has numerous advantages:

a) users control animation with the built-in Google Earth timeline slider

b) user zoom into and pan around detailed geographic features with familiar GE controls

c) users understand the location of the featured map in reference to any location on the globe

d) historical interpretation, source information, and legends may be inserted to appear with the map in the same browser window (which is possible with the Google Earth browser plug-in, but not feasible with traditional stand-alone Google Earth software)

However, we have not yet found a satisfactory way to convert all types of ArcGIS maps (such as the dot-density map further above) into KML format.

We also are investigating two other approaches to web-based animated maps with timelines:

5) VisualEyes (formerly HistoryBrowser, http://www.viseyes.org) is a Flash-driven generative browser that allows users to code their own spatial-temporal products, such as animated timeline maps with historical narration, such as the “Vinegar Hill” urban renewal project (http://www.viseyes.org/show/?base=vh). While extremely versatile, with GIS data and zoom-in capabilities, the tool creates digital products that stand alone on geographic space, rather than part of the globe (like Google Earth or HyperCities).

6) OpenLayers (http://www.openlayers.org) is a JavaScript library for displaying map data in browser windows, similar to Google Maps API, but developed for and by the Open Source software community. See interesting examples that link data charts with animated timeline maps, such as map of the spread of the H1N1 virus by Mesa Analytics (http://h1n1.mesaac.com).

See also additional resources on digital cartography and time-series visualization:

Cartography 2.0: Your Guide to Animated and Interactive Maps (free on-line knowledge base and e-textbook)

Last updated on November 5, 2009