Interactivity Types in Geographic Visualization

Article excerpt

Introduction

This paper provides a preliminary typology of interactivity appropriate for geographic visualization (GVis or geovisualization). Geovisualization arose from efforts in the 1980s to scientifically visualize the large volumes of data then emerging from space-based remote sensing platforms and other data collection devices (McCormick et al. 1987). As applied by cartographers and geographers, visualization in scientific computing (ViSC) initially was extended to explicitly include human problem solving:

 
   "Geographic visualization will be defined here as the use of concrete 
   visual representations--whether on paper or through computer displays or 
   other media--to make spatial contexts, and problems visible, so as to 
   engage the most powerful human information-processing abilities, those 
   associated with vision" (MacEachren 1992, p. 101). 

Geovisualization can therefore be defined as a method and approach for the visualization of geographic data in order to explore patterns, generate hypotheses, recognize connections or disruptions, and identify trends. While it is technically conceivable to conduct GVis in a non-digital media (Knowles 2000), more recent work has tended to emphasize environments with a high degree of interactivity between the user and the display. Geographic visualization is often characterized in the following tripartite scheme: as highly interactive, highly exploratory, and typically pursued privately, that is, in the research lab (MacEachren 1995; MacEachren and Taylor 1994). The original Working Group on Visualization of the International Cartographic Association (ICA) employed the notion of "cartography (3)" to capture this tripartite nature of true cartographic visualization (the working group is now known as the Commission on Visualization and Virtual Environments, see MacEachren and Kraak 2001). These three aspects differentiate GVis from traditional, static cartography, which is marked by low interactivity, the presentation or communication of known information, and is done publicly (that is, it is published).

A clear example of the exploration of unknowns is knowledge discovery in databases (KDD) or data mining (Fayyad et al.1996; Frawley et al.1992) which identifies and extracts useful information from databases. Yet it is less clear what it means to speak of interactivity, especially to distinguish "higher" from "lower" interactivity. One objection which has been made to GVis is that it does not provide anything new because ordinary traditional maps can also be interacted with. Examples of such interactivity may include looking over them, comparing them to the environment, tracing routes across them, navigating with them, judging areal extent or change, and so on. Here the user is interacting with the map in quite sophisticated ways, which demands a high cognitive load. Despite this, it appears advantageous to retain a distinct meaning for interactivity in a typical geovisualization environment if only because there are additional types of interactivity therein.

In this paper I provide a preliminary typology of interactivity which might be employed in GVis and turn aside the claim that GVis cannot uniquely provide high levels of interactivity. It shall be seen that the interactivity discussed is beyond the capability of the static map environment and that, therefore, GVis does truly offer something new (though this should be read as an expansion of the cartographer's toolbox, not as a replacement of traditional techniques). In addition, it is possible to combine these types of interactivity in interesting ways in order to make more sophisticated interactive environments. However, interactive mapping environments vary widely in sophistication, as a brief examination of two popular systems (MapQuest and ArcView) indicates. The typology outlined here will enable the development of a formal way of assessing the level of sophistication, and will help conceptualize other interactive environments built from the basic types. …