UNIT 47: ON-SCREEN VISUALIZATION

Written by Robert M. Edsall, Department of Geography, Penn State University



Context


Effective interpretation of the results of your analysis -- both by you and by others -- depends to a large extent on the design of the on-screen display. Visualizing information in the form of a map, chart, image, or other form of graphic takes advantage of humans' most perceptive sense -- vision -- to uncover patterns, associations, and processes that would likely be missed if the data were displayed in tabular or some other non-graphic form. However, as Buttenfield (1996) points out, it's this very ability that might lead a viewer of a graphic display to be as easily misled as informed by the contents of the graphic. A slight alteration of the color scheme or classification method of a map, for example, might produce two different graphics that appear to tell two very different stories -- even though they represent the exact same data. Thus it is crucial that GIS users be aware of the power of a graphic image to communicate ideas and of the considerations necessary to design an effective on-screen visual display. This unit will outline some guidelines, developed by cartographers over many decades, which will assist you in the logical design of easily understood GIS display.


Example Application

Guidelines for on-screen visualization should be applied to all situations which require the production of some graphic display of information. In a GIS context, this includes almost every possible application. No one application can incorporate all of the guidelines covered in this unit; the following is chosen because is represents a relatively complex but not uncommon situation encountered in GIS use.

A GIS specialist has been asked to produce a map showing possible environmental and social impacts of the construction of a new four-mile highway in a rural area. The specialist is faced with a host of choices, completely separate from any geographical analysis of the impacts, concerning how best to visualize the multiple variables of various types on a single display. The data she has been asked to include is the following:

This task requires careful selection, simplification, and classification of the data given and creative use of visual variables like shape, texture, location, hue, and lightness to create a cogent, easily understood, and informative graphic. Each choice she makes will impact the overall look of the graphic, altering its visual balance, contrast, and, ultimately, the information communicated by the display.


Learning Objectives

Awareness

The student should be aware, in a general sense, of visualization design concerns and strategies

Competency

The student will:

Mastery


Preparatory Units

Unit 10 - Projecting Data
Unit 11 - Register and conflate data
Unit 23 - Creating maps with CAD


Awareness

GIS and Visualization

General Considerations


Competency

Form of the map

Selection and Generalization

Data classification guidelines

Color use guidelines

Use of other visual variables

Legend design

Use of Text on the Display


Mastery

Form of the map

Data classification guidelines

Color use guidelines


Example Application Revisited


Follow-Up Units

Unit 48 - Designing products for printing
Unit 51 - Preparing Digital Presentations


Resources

The International Cartographic Association's Commission on Visualization web site includes many current theoretical and practical discussions about visualization as it applies to geography and cartography.

Brewer, C. (1994). "Color Use Guidelines for Mapping and Visualization," in Visualization in Modern Cartography, A.M.MacEachren and D.R.F.Taylor, eds. London:Pergamon. pp. 123-148.

A comprehensive guide to the logical use of color in cartographic and visualization applications.

Buttenfield, Barbara P. (1996). "Scientific Visualization for Environmental Modeling: Interactive and Proactive Graphics." GIS and Environmental Modeling: Progress and Research Issues, Goodchild, M.F., et al., eds. Fort Collins, CO: GIS World Books. pp. 463-468.

This article and several others in this volume discuss visualization strategies in the context of GIS.

Hearnshaw, H. and Unwin, D. eds. (1994). Visualization in Geographical Information Systems, New York: Wiley & Sons. 243 pp.

A set of papers on visualziation and GIS written by professors and other professionals in the field. Good for in-depth consideration of a variety of different issues in GIS.

Imhof, E. (1975). "Positioning Names on Maps," The American Cartographer, 2(2): 128-44.

MacEachren, A.M. (1994). Some Truth with Maps: A Primer on Symbolization and Design. Washington: AAG. 129 pp.

A very readable primer on cartographic techniques, tips, and pitfalls, with many illustrations.

Monomier,M. (1991). How to Lie with Maps. Chicago: U. of Chicago. 176 pp.

A fascinating discussion, with many graphic examples, of the ways in which cartography can be manipulated and manipulative. Monmonier has also written other books and articles on the subject which are also worth investigating.

Robinson, Arthur H., Joel L. Morrison, Phillip C. Muehrcke, A. Jon Kimmerling, and Stephen C. Guptill (1995). Elements of Cartography, sixth edition. New York: Wiley & Sons. 674 pp.

A standard introductory cartography texts used in American universities.