Terry A. Slocum

Evaluating the Usability of a Tool for Visualizing the Uncertainty of the Future Global Water Balance

We describe the development of software that is intended to enable decision makers (and their scientific advisors) to visualize uncertainties associated with the future global water balance. This is an important task because the future water balance is a function of numerous factors that are not precisely known, including the historical climatology, the model of potential evapotranspiration, the soil water holding capacity, and the global circulation models (GCMs) used to predict the effect of increased CO2 in the atmosphere. In developing the software, we utilized the principles of usability engineering. In our case, we utilized six steps: prototype development, evaluation by domain experts, software revision, evaluation by usability experts, software revision, and evaluation by decision makers. Although this approach led to an improved piece of software, decision makers should have been involved earlier in the software design process, possibly at step two (instead of the domain experts). Decision makers found the notion of uncertainty discomforting, but their positive comments regarding the software suggest that it could prove beneficial, especially with improvements in spatial and temporal resolution. One interesting characteristic of our approach was the utilization of a wall-size display measuring 25 x 6 feet. The wall-size display engendered great interest, but determining whether it is truly effective will require a study that directly compares it with more traditional approaches.

Design and evaluation of a decision support system in a water balance application

Abstract Visualization has become a vital tool for representing the results of scientific models in decision support applications. Both the raw data and the models from which these visualizations are derived usually have considerable uncertainty associated with them. Decision-makers are typically presented with results from these models with little or no insight as to the reliability of the information shown. For effective decisions to be made, a decision support system should allow collaborative participation from scientists and decision-makers, and it should display the locations, magnitudes, and sources of uncertainty in the results. This research work discusses a software application for visualizing the results of a water balance model and its associated uncertainty. The effectiveness of the application and its visual presentation methods were incrementally tested and improved through usability engineering principles.

A Qualitative Evaluation of MapTime, A Program For Exploring Spatiotemporal Point Data

The purpose of this paper is twofold: (1) to provide a user evaluation of MapTime, a software package for exploring spatiotemporal data associated with point locations, and (2) to examine some cognitive issues associated with the display of a dynamic geographic phenomenon - the change in population for cities over time. The methodology consists of a combination of individual interviews and focus groups conducted for three distinct groups of participants: novices, geography students, and domain experts. Some of the key findings are (1) that people do not naturally think of time lines in association with time (clocks and calendars are more common), which raises questions about the use of a linear time line for controlling animations; (2) that pictographic symbols tend to be preferred over geometric symbols for static maps, but pictographic symbols are apt to be too complex for animated maps; (3) that animations, small multiples, and change maps all have important roles to play in examining spatiotemporal da...

MapTime: Software for Exploring Spatiotemporal Data Associated with Point Locations

We introduce MapTime, a software package for exploring spatiotemporal data associated with point locations. Three basic exploration methods are available in Map-Time: animation, small multiples, and change maps. Animated maps can be presented either automatically (at a specified frame rate) or under user control (by dragging a scroll box along a scroll bar). We found the user-controlled approach most effective, but this and other Map-Time features ultimately need to be evaluated by map users. Potential research issues related to animation include developing a temporal legend that can facilitate understanding animations (a key problem is associating the correct dates with changes in the spatiotemporal pattern) and selecting an appropriate frame rate for the automatic display of various phenomena. Small multiples involve presenting multiple temporal elements simultaneously; they are thus useful for comparing individual temporal elements with one another. We argue that small multiples could be particularly u...

Knowledge Acquisition from Choropleth Maps

Todays computer graphics technology enables map users to acquire spatial knowledge in ways not possible with traditional static displays; for example, classes of data on a choropleth map can be sequenced from low to high values. Although sequencing and related approaches are often judged to be novel and exciting, it is unknown whether such approaches enhance or diminish knowledge acquisition. In a broader vein, we might ask what is the optimal technique for acquiring knowledge from a choropleth map? The optimal technique might involve a novel display approach, or modifying a method for learning a traditional static display. In this vein, two experiments were conducted. In the first, learning procedures common to experienced choropleth map users were ascertained. Using these procedures and others developed in a prior study, and their knowledge as cartographers, the authors developed a set of presumably effective procedures. In the second experiment, three choropleth display approaches were compared for th...

Analysis of Thematic Maps Published in Two Geographical Journals in the Twentieth Century

This article examines changes in the design of thematic maps in two geographical journals (the Annals of the Association of American Geographers and The Geographical Journal) over the course of the twentieth century. We analyzed the design of thematic maps using both qualitative and quantitative content analyses. The qualitative content analysis involved writing positive and negative comments pertaining to eleven map design elements. For the quantitative content analysis, we created a set of seventeen items based on many of these same map design elements, but for each item there was a fixed set of possible nominal or ordinal-level responses. We also rated the overall effectiveness of map design using a ten-point scale. The overall design rating revealed a significant, albeit gradual, improvement in map design over the twentieth century, with considerable variation for individual years. The quantitative content analysis suggested that the improvement in map design over time was a function of improved readability and visual hierarchy and to some extent an improved logic of symbology (the latter was not significant over time). Perhaps more interesting were the summary statistics for certain map design elements. For instance, a source was not included on the majority of maps even though we felt that the maps could have been interpreted more effectively if a source were included. Another interesting finding was that thematic maps frequently fell in to what we describe as a miscellaneous category. Choropleth, dot, and other familiar thematic map symbolization types were much less common and their frequency varied considerably from year to year. Overall, our results are disconcerting because the quality of map design in these journals did not reflect our disciplines long interest in mapping and the importance of cartography to geography.

Evaluating the Potential of the GeoWall for Geographic Education

Abstract This article discusses modern stereoscopic displays for geographic education, focusing on a large-format display—the GeoWall. To evaluate the potential of the GeoWall, geography instructors were asked to express their reactions to images viewed on the GeoWall during a focus group experiment. Instructors overwhelmingly supported using the GeoWall, stressing the 3-D (three-dimensional) realism provided by stereo images and the excitement these images likely would generate for students. Instructors did, however, note a number of limitations of the GeoWall, including the need to create stereo images (e.g., traditional nonstereo photographs cannot easily be converted to stereo), the need to wear special glasses, and the fact that some people cannot see in stereo. In general, it appeared that the GeoWall would be most useful for complex images and tasks.

Modeling and visualizing uncertainty in a global water balance model

Public policy makers and others wishing to understand the potential impact of our actions on the environment need a tool to simulate and visualize relevant processes. Present models and the data on which they operate have considerable variability which translates into uncertainty in model results. Decision makers must understand and consider not only raw model results, but also the uncertainties associated with them. As an example, we describe a tool that evaluates a global water balance model and presents visualizations of both the results and the associated uncertainties.

CHAPTER 9 - Cartographic Data Display

Publisher Summary The present era is exciting for those interested in cartographic data display. It has entered an arena where technological developments and marketplace forces have placed powerful, but affordable, computers on desktops and in laboratories. These computers allow creating map displays that were dreamed about a short time ago. This chapter discusses some of the changes that have led to present capabilities. These changes can be grouped into: (1) improvements in hardware, (2) improvements in software, and (3) the merging of the geographic techniques subfields of geographic information systems (GIS), remote sensing, spatial analysis (quantitative methods), and cartography. The chapter focuses on the recent developments that go beyond the display methods that traditional manual cartography has produced. It provides with some sense of what has been done and what needs to be done in the future. y.

Using Visual Basic to Teach Programming for Geographers

Abstract We describe a course in which the programming language Visual Basic was used to teach programming for geographers. Although the functionality present in commercial off-the-shelf applications has led to the demise of computer programming instruction in geography, we feel there are several reasons why programming should be taught: 1) experience attained may be applied when using macro (scripting) languages in commercial GIS packages and when manipulating sophisticated visualization software, 2) students develop a deeper understanding of general hardware and software capabilities, 3) experience with programming makes students appreciative of the difficulty and time that good programming requires, and 4) resulting applications will function precisely as desired. Fortunately, modern programming languages, such as Visual Basic, ease the burden of programming and still provide these advantages. Distinct advantages of Visual Basic include its low cost, ease of developing interfaces, and links with standa...