Commission
on Visualization - A research agenda for the 21st century
Much
of the research cited above appeared in a special issue of Computers
& Geoscience (May, 1997) or in the Proceedings of the
June, 1997 ICA Conference in Stockholm, or in a forthcoming special
issue of the International Journal for Geographical Information Science.
Just prior to the Stockholm conference, the Commission met for three
days in Gävle, Sweden to concentrate on developing a comprehensive
research agenda designed to set research priorities that will lead
GVis (and the Commission) into the 21st century. This research agenda
is still a work in progress and is presented as a draft outline below.
Details will be filled in over the next six months.
Research
priorities are categorized under four themes that reflect several
aspects of visualization as an interaction between humans and computers
directed toward exploring and understanding geographic phenomena.
These four themes are outlined below.
1.
Representation
Perhaps
the most obvious research focus for cartographic visualization of
georeferenced information involves issues of the visual display itself.
1.1
Extending the object of representation
It is
clear that the integration of ViSC and VR tools with cartographic
tools extends the object(s) of geographic representation in various
ways. Some of these ways were identified in initial goals of the commission:
the representation of space time phenomena and processes and the representation
of data reliability. To this list, a need has been identified to develop
methods for the visualization of algorithms used to process spatial
data, the visualization of data structures and query processes, and
the application of GVis methods to spatialization of information in
general (i.e., of non-spatial information).
1.2
Extending forms of representation
As a
complement to extending the range of objects to which GVis methods
are applied, substantial research effort must be directed to taking
advantages of advances in computer graphics that make the new forms
of representation possible. Much of the initial GVis research has
concentrated on adding dynamic components to traditional 2D and 2.5D
representational forms (e.g., animated planimetric maps and flythroughs
of perspective views). Priority areas identified for research emphasize
two developments, the rapid increase in computer power that makes
dynamic manipulation of map parameters possible and the increasing
availability of tools for building virtual environments. Research
is needed to determine how to integrate methods for dynamic manipulation
into GVis tools (e.g., to merge exploratory data analysis methods
with map animation) and to integrate VR technology with geographic
data and principles of geographic representation (e.g., adding geofunctions
to VRML or using immersive VR to explore abstract georeferenced data,
such as output from a global climate model).
In addition
to research on the technical problems of using new technology to best
advantage, research is also needed to consider the implications of
new representation forms. Questions here relate to the semiotics of
extended representational environments, the relative merits of abstract
versus realistic representations, and what the concept of representation
means in a virtual world. One component of an approach to addressing
these questions involves considering cognitive aspects of visualization
tool use (detailed below). In addition, these questions can (and should)
be approached from the perspective of the philosophy and sociology
of science.
2.
Interface design
The
Commission has, from the start, directed attention to extending cartographic
principles, developed for static maps, into the realm of dynamic maps
and related displays. In addition to research focused on what and
how we represent georeferenced information, therefore, attention must
also be directed to mechanisms we provide that allow users to interact
with those representations. Research priorities identified here relate
to the following:
2.1
Typology of visualization operations
Cartographers
have directed considerable attention to developing typologies of variables
used in visual (and tactual and sonic) geographic representation and
guidelines about appropriate use of those variables. To develop a
coordinated approach to interaction with manipulable maps, however,
it is essential that a complementary typology of visualization operations
be developed. A step in this direction is a typology proposed by Keller
and Keller (1992), but that typology does not focus specifically on
visualization of georeferenced information, nor does it consider the
need to integrate visualization operations with query operations in
the context of GIS-GVis integration (see below).
2.2
Controls for operations
Interactive
displays of georeferenced information require development of controls
through which users can interact. Although there are many basic tools
generally available that can be adapted for use in GVis environments
(e.g, buttons, sliders, etc.), there has been no systematic attempt
to develop a typology of control forms for manipulation of spatiotemporal
information. Developing such a typology could lead to more consistent
interfaces for geoinformation processing environments and more logical
matches between operations and controls.
2.3
Facilitating information access in complex hyperlinked information
archives
As the
World Wide Web and related technologies provide a mechanism to link
geoinformation in complex ways, there is a critical need for research
directed to methods that facilitate navigation through that web of
information. Potentially productive approaches involve the development
of appropriate metaphors for navigation in these complex information
spaces and the spatialization of non-spatial information as a method
to identify relationships among information objects.
2.4
Intelligent GeoAgents
An intelligent
GeoAgent can be defined as a virtual entity that understands our needs
and prefrences related to geographic data access and/or its analysis
and representation. Intelligent GeoAgents should act as filters and
interpreters of information and contexts. One potential role for intelligent
GeoAgents involves embedding cartographic expertise within database
objects to be displayed. Each object could be bound with a GeoAgent
that evaluates the context of use and the display context within which
the object finds itself, and select a display form accordingly. Another
role for GeoAgents is as information seekers that search the web for
information that meets criteria of a fuzzy query. The GeoAgent would
adjust to the information context it finds itself in, adapting the
query parameters in response to such things as links found among information
objects, density of information in particular locations within attribute
space, or simply success at matching the initial query.
2.5
Collaborative visualization
An emerging
area of research in ViSC generally is collaborative visualization--the
development of environments that facilitate the use of manipulable
visual displays for exploration of ideas and/or decision making by
two or more individuals (perhaps located at a distance). Tools for
collaborative visualization of georeferenced information have considerable
potential for use in contexts such as urban planning, environmental
management, and scientific interpretation of models of climate or
other environmental processes.
3.
Database-visualization links
One
of the most common arguments for developing visualization tools is
that such tools can help us cope with the rapidly increasing volume
of information being generated by our information society. This potential
can only be realized in the case of GVis, however, if GVis is integrated
with other technologies for storage, access and analysis of that georeferenced
information. Three key research priorities are identified in this
context.
3.1
GIS-GVis integration
Traditional
GIS environments have treated visual display as an output, thus an
endpoint of a query or analysis process. GVis, on the other hand emphasizes
information exploration and hypothesis generation, thus it is as likely
to produce queries as be the result of one. For GVis to reach
its potential, a new view of both GIS and GVis system design is required.
Research must address the range of issues associated with merging
the goals and functions of GIS and GVis.
3.2
Spatial data mining-GVis integration
As data
volumes continue to increase, methods of "mining" data are being
developed to sift through the vast amount of information in a search
for interesting patterns and relationships. Visualization has a potential
role at all stages of the data mining process (from preprocessing
and error identification through selection of information to be mined,
to interpretation of results from data mining). For georeferenced
information, this integration of GVis in the data mining process will
require, not only adaptation of approaches to data mining that recognize
the unique properties of spatial information, but the adaptation of
GIS tools to facilitate the application of both GVis and data mining
methods.
3.3
Generalization and Visualization
Research
priorities discussed under this theme were prompted by a joint session
of the Commission on Visualization and the Working Group on Generalization
that took place in Gävle, Sweden, June, 1997. Many applications
of GVis require a facility to change spatial or temporal scale. Dynamic
visualization offers several new challenges for research in generalization.
One is to develop methods for making effective use of the level of
detail node in VRML, in order to achieve an appearance of seamless
change in scale--a problem that requires adapting many generalization
concepts developed for 2D maps to 3D worlds. Similarly, the emphasis
on spatiotemporal information characteristic of many GVis applications
creates a need to begin to address issues in spatiotemporal generalization.
A third generalization issue needing attention involves the generalization
of hyperlinked networks of information. Just as a base map with too
much detail can impede visual analysis of thematic information superimposed
on that base, a too detailed network of links among information objects
can impede visual exploration, searching, or decision making based
on that network of information. Methods to generalize these networks
are needed. Cartographic generalization is, of course, an active research
area in its own right replete with many unanswered questions. One
avenue of GVis research with potential to support advances in generalization
research involves the use of GVis methods to facilitate understanding
of the generalization process.
4.
Cognitive aspects of visualization tool use
The
promise of visualization is based on an assumption that human vision
and cognition has powerful information synthesis and pattern seeking
capabilities that can effectively complement the raw information processing
power of digital computers. Harnessing this power of vision, however,
requires developing a more complete understanding of spatial cognition
and perception of visual displays. While we have a solid base of knowledge
about perception and cognition as it relates to static paper maps,
we know much less about the cognitive and perceptual issues associated
with 3D and dynamic displays. Seven priority topics are identified
here.
4.1
Cognitive aspects of dynamic representation
Our
knowledge of cognition related to dynamic scenes (even real world
scenes) is limited. Key questions relate to issues such as the role
of animation in understanding process, the implications of various
parameters of an animation (e.g., display changes per second, smoothness
of transition between frames, etc.) on that understanding, differences
in cognitive processing required to interpret temporal versus nontemporal
animation, and methods of retaining orientation in flythroughs.
4.2
3D representation and virtuality
As technology
makes it possible to create increasingly realistic representations
of the geographic environment, it is important to consider the cognitive
implications of this realism. Questions to be addressed include the
cognitive processes involved in identifying the correspondence between
2D (planimetric) representations and 3D representation, exploring
the changing relationship between sign-vehicles and referents as representations
become increasingly realistic, and developing and understanding of
the integration of visual and sonic information in the context of
immersive and non-immersive virtual worlds.
4.3
Schemata, metaphors, and human-computer interaction
Facilitating
human-computer interaction requires development of logical approaches
to interface design and the creation of appropriate interface controls
that allow users to manipulate parameters of the display. Also required,
however, is a comprehensive understanding of the cognitive aspects
of interaction with the display. Do, for example, different control
forms (e.g., a time wheel versus a time line) prompt different knowledge
schemata that result in different interpretations of what is seen?
A similar question involves the implications of possible interface
metaphors for the strategies that a user takes to data exploration
and the interpretation of results from that exploration.
4.4
Hypermedia navigation
The
web is a complex maze of information in which users frequently are
frustrated in their efforts to locate the information they require.
Attention to cognitive aspects of wayfinding in this information environment
is needed as a complement to research (discussed above) directed to
design of interface tools that facilitate information browsing. One
potentially fruitful avenue of research is to explore the transferability
of conceptual models of wayfinding in real spaces to wayfinding in
information spaces. An additional topic to investigate involves strategies
used to maintain orientation and context in multidimensional information
spaces.
4.5
Expert-novice distinctions
At issue
here is the impact of expertise on use of GVis and differences in
design strategies that should be developed for GVis users with differing
kinds or levels of expertise. At least two forms of expertise must
be considered, that in the technology being used and that in the domain
of knowledge to which the technology is applied. A better understanding
of expert strategies for the application of GVis tools to data exploration
or problem solving could be used to design knowledge-based GVis tools
that prompt novices to use expert strategies.
4.6
Influence of GVis methods on the scientific process / scientific understanding
There
is an implicit assumption behind ViSC that visualization will facilitate
science. While anecdotal evidence may seem to support this contention,
anecdotal evidence by its nature is generally positive. There is little
systematically collected empirical evidence to either support or refute
the claim and we know relatively little about how scientists actually
use sophisticated visualization tools and methods. Research is required
to test the underlying assumption that GVis facilitates science and
to develop an understanding of the implications for science of visual
geographic representation methods.
4.7
Role of visualization in decision-making
The
primary question here is whether GVis tools change how decisions are
arrived at and/or the outcome of decisions. Assuming that some changes
are produced, it is important to explore the nature of those changes
and whether decisions are more consistent or otherwise "better."
Additional questions to address include the implications of various
components of a GVis environment on decision making (e.g., the kinds
of information displays provided, the kinds of interaction allowed,
etc.) and the role of data reliability visualization on strategies
taken to decision making.
Conclusions
As indicated
in the Terms of Reference, the goals of the Commission for the next
four years are directed toward advancing science related to map-based
visualization of georeferenced information and to potential applications
of that research. While we anticipate contributions to sceince and
its applications by many individuals involved with the Commission
(directly and indirectly) the primary role that the Commission has
served, and will continue to serve, is as a bridge among cartographic
researchers in different countries as well as a bridge between cartographic
researchers and other scientists (and engineers) working on related
questions. Terms of reference 3, 4, and 5 will facilitate this bridging
and by doing so, will make accomplishing the first two terms possible.
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