Introduction

The nature of maps and of their use in science and society is in the midst of remarkable change - change that is stimulated by a combination of new scientific and societal needs for geo-referenced information and rapidly evolving technologies that can provide that information in innovative ways. A key issue at the heart of this change is the concept of "visualization." Cartographers can rightly argue that we have always been involved with visualization, in the sense of "to make visible," (see Freitag, 1993, Rimbert, 1993, and Wood, 1994 for discussion of this use of the term visualization and its links to cartography). To treat current conceptions of visualization as "nothing new," however, is to misunderstand the alternative definitions of "visualization" used beyond our discipline - definitions that are linked to specific ways in which modern computer technology facilitates the process of making visible in real time (see Taylor, 1991 and 1994 for a cartographic interpretation of visualization from this perspective - as the intersection of representation methods, cognition and analysis, and computer techniques). The ability to prompt instantaneous changes in maps results not only in a quantitative difference in the number of things a user can make visible, but a qualitative difference in the way users think - and in turn in the way maps function (Wood, 1994). To ignore this qualitative difference in map use (associated with visualization in the sense implied by the term "scientific visualization") has the potential to leave cartographers in the position that Barbara Petchenik (1989, p. 48) warned us about several years ago (in relation to the map's role as a travel aid), "as keepers of an arcane, possibly even obsolete craft/technology."

Cartography as a discipline has a significant stake in the evolving role of maps within systems for scientific visualization, within spatial decision support systems, within hypermedia information access systems, and within virtual reality environments (see Artimo, 1994 for discussion of implications of the latter two). The ICA can and should take an international leadership role in directing and facilitating the inevitable changes in maps and mapping brought about via the advent of scientific visualization (and related visual and/or spatial information processing technologies) and the associated reemphasis on the power of visual evidence. We have much to offer the scientific community through our long history of design and production of visual representations of the earth, our knowledge of geographical (and cartographical) information systems, and our experience with linking digital and visual geographic representations. We also have much to gain from the wider scientific visualization community where approaches to interactive computer tool development, interface design, three-dimensional computer modeling, etc. are more fully developed. One goal of the proposed Commission, therefore, is to facilitate stronger ties to the wider scientific visualization community.

The proposed Commission on Visualization will balance attention on computer technology with attention on how maps are used to facilitate thinking and decision support. Thus, the commission builds from accomplishments of several existing and past ICA Commissions/Working Groups, notably the Commissions on Map and Spatial Data Use and on Advanced Technology and the Working Group to Define the Main Theoretical Issues in Cartography. The proposed Commission on Visualization is intended to complement (not replicate) these other efforts (some of which are ongoing).

Cartographers have devoted considerable attention over the past decades to understanding how presentation maps work (what Freitag, 1993, terms the "communication function" of maps). We, however, know relatively little about how maps that facilitate thinking, problem solving, and decision making work (uses that, according to Freitag's, 1993 typology, are representative of the "cognitive function" and the "decision support function" for maps), nor what the implications of "working" are in these contexts (implications associated with Freitag's, 1993 "social function" and Török's, 1993, "social context" - the latter derived largely from Harley's 1988, 1989 approach to the ideology of mapping). It is to the cognitive and decision-support functions that much of the new geo-information technologies are directed -- particularly those maps with dynamic and interactive components. It is also in these functions that scientific visualization and cartography share the greatest overlap - an area that has been labeled "Geographic Visualization" (see MacEachren and Monmonier, 1992 and MacEachren, 1994). The main goals of the proposed Commission on Visualization are (1) to begin filling the void in understanding how digital geo-information technology interacts with the cognitive and decision-support functions of maps, and (2) to help cartographers make the transition from being designers of maps to designers of map-based thinking and decision-support tools. A secondary goal is to consider how geo-information technology applied to geographic thinking and decision-support interacts with the social functions of maps and the social context of map use.

Approaches to Visualization in Cartography

Use of the term visualization in the cartographic literature can be traced back at least four decades (Philbrick, 1953). It was the 1987 publication of a report by the U. S. National Science Foundation, however, that established a new meaning for this term in the context of scientific research (McCormick et al., 1987). The report, produced by a committee containing no cartographers, emphasized the role of computer display technology in prompting mental visualization - and subsequent insight. Scientific visualization has, thus, been defined as the use of sophisticated computing technology to create visual displays, the goal of which is to facilitate thinking and problem solving. Emphasis is not on storing knowledge but on knowledge construction. In relation to the spatial information processing goals for maps delineated by Rimbert (1993), "spatial analysis" and "spatial simulation" could be considered prototypical components of scientific visualization. Rimbert's "travel guide," "spatial inventory," and "secondary information source" goals, in contrast, would be considered (at least by researchers in scientific visualization) to be ancillary to the visualization process.

Following publication of the McCormick report on visualization in scientific computing, several cartographers took up the challenge of trying to grapple with the cartographic implications of this new (or renewed) reliance on visual representation in science. DiBiase (1990) borrowed from the exploratory data analysis literature of statistics to propose a model of stages in map-based scientific visualization applied to the earth sciences (Figure 1: DiBiase's (1990) model of the role of maps in scientific visualization.). This model focused on the need for cartographers to direct attention to the role of maps at the early (private) stages of scientific research where maps and map-based tools are used to facilitate data sifting and exploration of extremely large data sets.

MacEachren and Ganter (1990), in a parallel effort, developed a simple cognitive model to identify key parts of the display-user interaction that occurs during exploratory map-based visual analysis (Figure 2: The Pattern-ID model for cartographic visualization proposed by MacEachren and Ganter (1990).). Their emphasis was on developing cartographic tools that prompt pattern identification and on the potential for visualization errors (errors that are similar in nature to the Type I and Type II errors associated with traditional statistically-based hypothesis testing). The related topic of data quality/reliability visualization has proved to be a particularly active research direction within cartographic visualization (e.g., MacEachren, 1992; Beard and Buttenfield, 1991; Buttenfield and Beard, 1994; Fisher, 1994, van der Wel, et al., 1994).

While the above conceptions of visualization in cartography put emphasis on the private-cognitive processes of visual thinking (particularly those associated with scientific hypothesis formulation and confirmation), Taylor (1991) directed attention to the place of visualization in the structure of cartography as a discipline (Figure 3: Taylor's (1991) conception of visualzation in cartography.). His model presented visualization as the intersection of research on cognition, communication, and formalism (with the latter implying strict adherence to rule structures dictated by digital computer systems). In a recent modification of this model (Taylor, 1994) has made it clear that he does not equate "visualization" with "cartography" (Figure 4: Taylor's (1994) extended and revised conception of visualization in cartography.). Instead, what he argues for is a view of visualization as a distinct development in cartography, and in science in general, that will have an impact on the three major aspects of cartography that he defines as the sides of his "conceptual basis" triangle (cognition and analysis, communication, and formalism).

Commission Focus: Map Use -- Technology Links

The approach taken toward cartographic visualization in the proposed commission evolved from the attempts (noted above) to explicate the relationship between cartography and scientific visualization and from ideas discussed within the Map and Spatial Data Use Commission: Working group on cartographic visualization. This sub-group was organized by Alan MacEachren (USA) at the request of Commission co-chairs James Carter (USA) and M. Konecny (Czech Republic). Correspondence has thus far been carried on among cartographers, computer scientists, psychologists, and geographers in Australia, Canada, Finland, Germany, Greece, Hungary, Netherlands, Sweden, the UK, and the USA. This sub-group held an open panel discussion in Cologne (organized and moderated by Alan MacEachren) during which a variety of views on visualization in cartography were presented by Daniel Dorling - UK, Menno-Jan Kraak - Netherlands, Michael Peterson - USA, Janos Szegö - Sweden, and Michael Wood - UK. and responded to by many other conference delegates. Various distinctions between visualization in cartography and other aspects of cartography were considered.

One outgrowth of these activities is a conception of the "space" of map use referred to by MacEachren (1994) as [cartography]3 (Figure 5 : MacEachren's (1994) [Cartography]3 perspective on map use.). In this space, visualization is considered to be the complement of communication. All map use involves both visualization (defined loosely as the prompting of visual thinking) and communication (defined loosely as the transfer of information), but map use can vary considerably in which is emphasized. The axes of the use space are delineated as private versus public, high interaction versus low interaction, presenting knowns (i.e., simple information retrieval) versus revealing unknowns. Past communication-oriented cartographic research has emphasized the use of static maps designed for public consumption with the emphasis on extraction of specific pieces of information (e.g., research on communication effectiveness of textbook or topographic maps). As a complement to this relatively long tradition of communication research, the proposed commission will target the other end of the map use cube - with emphasis on the role of highly interactive maps in individual and small group efforts at hypothesis generation, data analysis, and decision-support. Cartographic visualization is, thus, typified by private, highly interactive use of maps to reveal unknowns - but more broadly is taken to include any use combining two of the three criteria (e.g., highly interactive map displays targeted toward revealing unknowns but designed broadly enough to be useful in a public context, such as through the World Wide Web). Efforts of the commission will, as a consequence, extend to the three corners of use-space that combine two of the axis extremes (Figure 6 : Matrix of map use - corners of the "cube").

Examples of map use at the corners of the [Cartography]3 map use space (MacEachren, 1994).

In relation to the above conceptualization of visualization as it relates to cartography, a plethora of questions that might be addressed come to mind. A sampling of the specific issues that might be addressed through work of the proposed commission are listed below, along with one or two citations to published literature that has targeted these questions as deserving attention.

• investigation of the implications of a change from an approach to cartography that focused on optimal maps toward a multiple perspective approach - see Monmonier 1991 for an argument that single map solutions should be considered unethical.
• development of a conceptual model and associated tools for the visualization of spatial-temporal process information (see Slocum and Egbert, 1991, for a review of relevant work in cartographic animation, Board, 1993, for discussion of issues of spatial process as one of the main theoretical areas in cartography requiring attention and Kraak and MacEachren, 1994, for discussion of approaches to the representation of spatio-temporal information via maps).
• development of a conceptual model and associated tools for the visualization of data quality/reliability information - see Buttenfield and Beard, 1994 and van der Wel, et al., 1994 for alternative suggestions about where to start.
• study of methods for and implications of linking cartographic visualization tools to GIS (see Slocum et al, 1994 for one attempt to achieve this link).
• explore the impact of map-based spatial decision support tools on decision making strategies and on the outcome of decision-making - see Asche and Herrmann, 1993 for a description of a map-based visualization/decision support system, Armstrong, et al. 1992 for a taxonomy of decision-display types, and McGuinness for empirical methods suited to identifying strategies for use of visualization tools in decision making.
• study the potential of three-dimensional representation tools and the corresponding implications of both three-dimensional display and the associated general trend toward realism (versus abstraction) in scientific representation - see MacEachren, et al., 1992 for an initial discussion.
• address implications, for our approaches to map design, of the ability to link many representation forms together in hypermedia documents (e.g., maps, graphs, text, audio narratives, sonic data representation, etc.) - see work by Cartwright, 1994 for ideas concerning links between visualization and hypermedia.
• investigate alternative computer interface design strategies as they relate to use of visualization tools for hypothesis formulation and decision support - see Lindholm and Sarjakoski, 1994, for a conceptual outline of some possibilities.

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