Types of Graphical Illustration in Technical Writing

Graphics used in technical documentation serve a specific purpose - to present information in the clearest format possible for the reader. Basic graphic principles apply:

  • avoid clutter,
  • orient the image properly,
  • be aware of scale,
  • always verify content, and
  • avoid any graphic that is extraneous.

Graphics should never be used to dress up a document; they should only be used to enhance understanding. When principles of design replicate principles of thought, the act of arranging information becomes an act of insight (E. Tufte intro).

A reader's attention is drawn to graphics more than to blocks of text. The use of graphics enables writers to present technical information more clearly and emphatically than words alone. Therefore, graphics for a technical document must be designed, edited, and prepared with precision to avoid weakness. Readers often look at graphics quickly. The message in a figure or table should be clear and readily apparent. The writer should be familiar with the intended audience of the document so that the right graphics are selected. Each graphic should focus on clearly conveying one piece of information.

Uncomplicated graphics work best. Avoid what Edward Tufte calls "chart junk" (E. Tufte, Visual) that distracts the reader from the intended information the graphic is presenting. The Franklin Covey Style Guide for Business and Technical Communication provides comprehensive guidelines for each of the graphical components, and this wiki content text draws heavily upon it for both content and style recommendations (Franklin).

There are several types of graphics, each with its own function. Graphics can represent these elements in a technical document:

  • Numbers:
    • Tables
    • Graphs
      • Bar graphs
      • Line graphs
      • Pie graphs
    • Maps
  • Concepts:
    • Charts
      • Flow Charts
      • Organizational charts
      • Scheduling Charts
  • Objects:
    • Photographs
    • Illustrations
      • Drawings
      • Diagrams
      • Schematics
  • Words - Words emphasized by boxing them, by changing the color or the font, or enlarging them to call attention in a text are all forms of graphics, albeit not very sophisticated (McMurrey).

Visual techniques for depicting quantity include direct labels - for example, the numerically labeled grids of statistical graphics; encodings - for example, color scales; and self-representing scales - for example, objects of known size appearing in an image (E. Tufte 13).

Illustrations are classified as either tables or figures: if the illustration is not a table (information is presented in columns and rows), then it is a figure. Tables and illustrations are numbered independently; within each category, they are numbered sequentially.



Tables are the best graphic to use when readers need to focus on specifics. "A table is an effective display for two-dimensional data, usually when one dimension is a collection or series of items and the second dimension consists of attributes or characteristics that all or most of the items have in common, such as description, type, size, and color" (Gurak 357). Tables can communicate many details in a simple way; details that would be hard to comprehend if done through words alone. An advantage of tables is that they can be quickly scanned for information and that "commonalities and differences" across entries are readily apparent (Gurak 358).


Guidelines for Creating Tables

  • Explain what the table contains and how it will help the reader.
  • Give the table either a title or caption, as appropriate.
  • Write informative, understandable, and visually distinct heading labels.
  • Make rows distinct through headings or display of categories.
  • Avoid wordiness, limit text in cells to a few words.
  • Use color coding and symbols to facilitate quick scanning and data comparison.
  • Ensure the table will be readable in the display format.

Figure 1. Table of data for a steel wall product.



Graphs plot a set of points on a set of axes, usually along the horizontal (x) and vertical (y) axes, to show abstract information in an easy to understand way. They visually represent and compare numerical data, and as such are useful for showing trends, cycles, cumulative changes, relationships between variables, and distributions. Though not as effective as a table in presenting precise data, readers can "see in one image a trend or pattern within a large data set" (Gurak 319). Graphs are better than tables to show the meaning of data.

"Because graphs represent complex data in visual form, they can be powerful and persuasive"(Gurak 322). Therefore, one must be careful when creating graphs that information is not distorted or misrepresented, that resource information is accurate, and that the graph is clear and easy to read (Gurak).


Guidelines for Creating Graphs

  • Ensure the axes are clearly labeled, and that units of scale or measurement are identified (Gurak 323).
  • Ensure that axes that do not begin at zero are clearly labeled.
  • Ensure that the graph does not distort or modify the trend.
  • Indicate the source of data used to construct the graph.
  • Explain how the graph supports points discussed in the text.
  • Design for simplicity, avoid overuse of colors and typefaces.
  • Use software programs such as Microsoft Excel to create graphs.

Graphs should be numbered sequentially, include a title, and an informative caption which identifies the specific purpose of the graph. Warrant the source of the data contained in the graph with a footnote reference. Labels, numbers and letters should each be kept parallel with the horizontal axis.


Line Graphs

Line or coordinate graphs are plotted using grid lines, with a horizontal axis and a vertical axis. Labels and scales should indicate the quantity, magnitude and range of each axis. The key data lines should be made heavier than grid lines for less important data. Multiple lines can appear in the same chart to show different variables, and should appear in different colors or patterns to differentiate them (Franklin 108).

Line graphs are especially helpful to show several variables relating to one other variable. For example, time is the variable tracked in Figure 15.15, and several types of mortgage rates plotted over time. This creates a clear and simple visual comparison for the reader.

30-YearFRM, 15-Year FRM, 1-Year ARM Rates, 1992 - 2009
Figure 2. Mortgage interest rates from August 1992 through February 2009.


Bar Graphs

Bar graphs, as the name implies, use colored bars to depict a trend between two or more variables over time. "Most readers are familiar with bar graphs and can quickly grasp quantitative relationships by comparing the heights or lengths of the bars" (Gurak 319).

Bar graphs are not useful if the quantities shown do not differ significantly. Changing the axis scales to dramatize slight differences skews the reader's perception of the data.

Bar graphs can be horizontal or vertical - vertical bar graphs are considered better for showing trends and horizontal bar graphs are considered better for showing magnitude changes (Franklin 111).

Bars should be wider than the gaps between them, different patterns should be used to indicate differences and they should be labeled clearly.

external image horizbargraph.gif

Figure 3. Ozone concentration in locations A through E.


Pie Graphs

Pie graphs are circles divided into sectors, or slices, to show the relationship of parts to a whole. "Pie charts are often accompanied by numerical data presented as a spreadsheet or table to allow readers to explore the displayed information in more detail" (Gurak 271).

The sectors must add up to 100 percent. Pie graphs are useful for general comparisons of relative size, but they are not useful if accuracy is important. They are also not useful for showing a large number of items. Different colors and/or fill patterns should be used for adjacent pie sectors. Small percentage items should be grouped under a general label such as "Other" (Franklin 113).

Figure 4. Pie Chart of populations of English native speakers.



Maps, both 2D and 3D, represent many purposes from simple road maps to visualizing complex numerical data. "The design and content of a map depends on the purpose and type of map being constructed, the conventions for that type of map, and the audience using it" (Gurak 324).

To map sequential data, it is best to use gradations of one or two colors to show gradations in the data. But, to show differences "in kind rather than in amount", many colors may be used; choose colors that are easily distinguished from one another (Gurak 325- 326).



Charts are some of the most valuable and frequently used types of graphics. Charts have several conflicting definitions, depending on the resource consulted. For the purposes of our Style Guide, we will follow the style supported by the Franklin Covey Style Guide for Business and Technical Communication. Charts are graphs that do not rely on numerical interpretations, including organizational charts, flow charts, and schedule charts. The purpose of the chart, the audience, the medium, and the data and ideas being conveyed in the document should determine the best type of chart to use, rather than adhering to a hard rule (Franklin 42).

A chart is only as good as the effect it creates. A chart should only be included if it communicates information quickly and simply. Charts should be integrated with the text and convey information more dramatically than is possible without their use. A chart can both replace text and provide a visual road map that readers can use as they read through dense and complex material. Charts also provide a visual, which can aid recall. Flow charts, organization charts or scheduling charts should be used to help readers visualize the major points in a document.


Guidelines for Creating Charts

  • Ensure the chart is consistent with how the audience will view the data.
  • Design the chart so that it shows one primary idea or specific relationship.
  • Keep the chart simple and clear; do not include too much information.
  • Use clear, concise labels and titles; do not include too much text.
  • Ensure that the information is not distorted or misleading.
  • Use software programs such as Microsoft Excel to create charts.
  • Ensure the chart is easily read from one-page orientation.

Sequentially number and label all charts the same as other graphics contained within a document. Do not have a separate numbering scheme for charts. Place footnotes and warranting evidence below a chart.



A flowchart is a common type of chart, representing an algorithm or process, and showing the steps as boxes of various kinds, and their order by connecting these with arrows. Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields.

There are many different types of flowcharts for different users (such as analysts, designers, engineers, managers, or programmers) representing different types objects.


Four General Types of Flowcharts (Sterneckert)

  • Document
    • shows document flow through system
  • Data
    • shows data flows in a system
  • System
    • shows controls at a physical or resource level
  • Program
    • shows the controls in a program within a system (Business)


Features of a Flow Chart (Gurak 273)

  • Each step in the process is represented by a shape.
  • Decision steps are labeled in the form of a question. Different paths may be taken depending upon the answer to the question.

Figure 5. Flowchart representing steps for troubleshooting a broken lamp.


Organizational Chart

Organizational charts help readers visualize the structure and internal relationships of units or individuals within an organization.

Organizational Charts Typically Show:

  • divisions and subdivisions of the organization,
  • hierarchy and relationship of the groups to one another,
  • lines of responsibility and authority, where solid lines indicate direct lines of control, and
  • lines of communication and coordination through the use of dashed lines.

Figure 6. Organizational chart of the US government.


Scheduling Chart

A common project task is to schedule a series of events; the complexity of this task can vary considerably depending on how many steps are involved in the process.
Some common challenges are:

  • Resource Scheduling or the scheduling of people to work on and resources required by tasks.
  • Dealing with uncertainties in the estimates of the duration of each task.
  • Arranging tasks to meet various deadlines.
  • Juggling multiple projects simultaneously to meet a variety of requirements (Franklin 47).

A scheduling chart visually illustrates the steps and their dependencies in a process. There are several types of commonly used scheduling systems.


Examples of Scheduling Systems

  • Gantt,
  • MindMapper,
  • Fixed Point Chart (FPC), and
  • PERT (Program Evaluation and Review Technique) (Evaluation).

Figure 7. PERT Network Chart for a seven-month project with five milestones (10 through 50) and six activities (A through F).



Using photographs in technical documentation conveys realism and gives the document credibility. While current technology allows complete manipulation of a photograph, readers still like the realism a photo provides. Information about size and scale should remain constant throughout a set of related images - scale should be constant (E. Tufte, Visual Graphics 25).

Photographs are used to show a reader what is - or what can be - rather than conveying a concept. Selection of a photograph should always be done after text is written. Match the message you want to convey to the text as closely as possible. All photographs need to support the message - a project should have several photographs for each message, from different sources, from which to choose. Budget allowing, color photographs are preferred, unless your text has been written to convey a historical message and the use of sepia tones or black and white images enhances your message (Franklin 231).

Representational illustrations include many types of graphics such as diagrams and drawings of actual products that allow a reader to see what they look like in concept, or to see inside the product to places that are usually hidden or not viewable. These help the reader to visualize an idea or a relationship. Even rough sketches convey information better than words in many instances.


Types of Representational Illustrations

  • technical illustrations,
  • exploded-view drawings,
  • cutaway drawings, and
  • symbols and icons.

All types of illustrations should always be kept as simple as possible, with color used to enhance them. Sometimes in technical communications, full color may not be an option. In this case, working with two colors is preferred. The second color can highlight specific areas of an illustration to bring the reader's attention to that area.

Each illustration should be clearly labeled, with parts of the object shown.

When adding a series of illustrations, the viewing angle should be consistent for each figure.

All letters and numbers on the illustration should be numbered so they can be read without reorienting the book or manual. In a drawing showing a process, the flow of the process should read left-to-right (Franklin 120).

Figure 8. Illustration of a flying machine, by Leonardo da Vinci.


Technical Illustrations

Technical illustration is the use of illustration to visually communicate information of a technical nature. Technical illustrations can be component technical drawings or diagrams that aim to generate expressive images to effectively convey certain information visually to both technical and non-technical audiences. The visual image should be accurate in terms of dimensions and proportions, and should provide an overall impression of what an object is or does, to enhance the reader's understanding.

File:Interface lg.jpg

Figure 9. Technical illustration of an interface card conveying placement of the interface cable.


Exploded View Drawings

An exploded view, or assembly, drawing is a diagram, picture or technical drawing of an object showing the relationship or order of assembly of various parts.

The components of an object are shown slightly separated by distance - as if there had been a small controlled explosion emanating from the middle of the object, causing the object's parts to be separated an equal distance away form their original locations.

The exploded drawing is used in parts catalogs, assembly and maintenance manuals and other instructional material (Exploded).


Cutaway Drawings

A cutaway drawing, also called a cutaway diagram, is a 3D graphic, drawing, diagram and/or illustration, in which surface elements are selectively removed to make internal features visible, without sacrificing the outer context entirely (Cutaway).

Figure 10. Airplane hangar, showing exterior with cutouts to expose interior.


Symbols and Icons

Symbols and icons are very valuable technical communication tools in the global marketplace. Many symbols are considered "internationally recognized" and are used on signs in airports, train stations, and hospitals. These symbols are also used in manuals developed for international audiences. Incorporating symbols and icons into technical documentation can considerably reduce the number of words to describe something.

Figure 11. Recycling symbol.

Other types of graphics that may be used to add interest or humor to a document are clip art and cartoons.



Cartoons are drawn visuals that engage an audience through humor. Cartoons can be used to:

  • Introduce a general topic in a report or other document.
  • Provide a funny example to make a difficult topic understandable.
  • Connect with the audience to 'break the ice'.

"Humor, when used appropriately, offers an effective emotional appeal for persuasion. Showing a sense of humor can also build rapport with audiences" (Gurak 268).

To use humor effectively, the audience must not be offended, and must be able to see themselves in the situation. To do this, editors need to know their audience well. Because humor does not translate well across cultures, it is best to not use humor in international venues.

Cartoons can be found on newspaper and magazine websites as well as Comics.com and Slate.com. Be sure to cite the comic or source of the cartoon; and if the terms require, obtain the necessary permissions (Gurak). Audiences enjoy comic strips like Dilbert, "Because it reveals the absurd realities of many workplaces" (Gurak 269).


Clip Art

Clip Art is the simple, informal artwork associated with software programs like Word, or on the Web, or in clip art books. It is not necessarily humorous, and can be used to add interest to a document. It can also be used to highlight document text or guide the reader through the document. But like other graphics, it must be kept to a minimum so as not to look unprofessional.


Screen Captures

Screen captures are very helpful in technical documentation because they show the reader what an application looks like, rather than telling them. Seeing the actual screen is much more useful than describing it with words. Screen capture software may allow sections of a screen to be circled or numbered. Written instructions referring to these circles and numbers can help guide a user through a complex process.

Source: Norbert Elliot, http://elliotmedia.wikispaces.com/
Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.

Last modified: Wednesday, February 14, 2024, 6:43 PM