How to Create Descriptive Text for Graphs, Charts & other Diagrams

Text-only Version of Creating Descriptive Text Tutorial

When PDFs, PowerPoint presentations and other documents get published to the Web, informational formats such as diagrams, charts, graphs and tables - created from formulas that require extensive and precise as well as logical and understandable description- pose the greatest concern for accessibility. These formats are used not only in the classroom, but in research reports & articles, so the necessity of getting input from their content expert-usually the faculty member who conducted the research or developed the instructional material-is imperative. It is the content expert that needs to consider how best to describe the content and meaning of such informational images to audio "readers" of the document when making it electronically accessible to the public.

Background

To begin, it's important to understand that many persons with disabilities use assistive technologies as they surf the Web for information. Technologies like the screen reader, used by persons with learning disabilites as well as by blind and visually-impaired users, are programmed to read textual information aloud. Most such technologies, however, recognize and articulate only the information available to it-written and coded text-so that if images like diagrams and charts are incorporated into the document, they are overlooked and the user is often left completely unaware that there is additional visual information on the page.

Yet it is common to find complex informational images such as charts, data tables & diagrams published to the Web by scholars, scientists and other researchers. Unlike graphics that merely serve a decorative function, users of assistive technology miss out on significant information by not being able to interpret these blank images.

Sighted persons experience the visual equivalent of this phenomenon when we see how the scanned images used to create a PowerPoint presentation look as a Web page (HTML) version-a service the search engine Google automatically provides-when published on the internet.

As you can see, the information embedded in the map in the first slide, as well as that communicated by the pie charts in the second slide, get lumped together into one Web page because of the information now "missing" from the slide presentation. In similar fashion, some assistive technologies will not recognize and thus "skip over" important informational content and will communicate only slide titles and subtitles to users.

This phenomenon underscores the need to provide descriptive, "alternative" text for most of your images, whether used in PDF, PowerPoint, Web Page and even word-processed format. This alternative text, in its shortest form, is embodied in feature known as an Alt-text tag coded into a Web page or PDF document. When there is a lot of detailed information conveyed by an image--or when you are making a Word document or PowerPoint presentation accessible--a longer version of alternate text is needed in the form of a caption, D-Link or LongDescription.

Evaluating the Information in Your Images

Before creating alternative text for informational images, conduct a brief assessment of the nature and content of your image by examining three issues. First, determine:

Whether the information is presented in a written or alternative format elsewhere.

If this is the case, it becomes easy to copy, edit and paste portions of your existing documentation into the Alt-text and/or long description of the image in your new Webpage/PDF/PowerPoint or Word document, depending on its length. Sometimes, for example, converting information in a pie chart into readable text is fairly easy. This can save you a lot of time re-entering data and other types of information.

Whether the information in your diagram or chart is too extensive to describe easily.

If this is the case, it may be a better use of resources to use the services of your local Disabled Student Services Center, such as the McBurney Disability Resource Center on UW-Madison's campus. Remember, though, often such a Service Center as McBurney needs the help of a content expert (for instance, a meteorologist to explain the meaning of data on a chart of a high resolution radiometry such as the one above), and that they also need time to process requests for assistance.

Whether some of the information can be eliminated from the accessible document.

How you eliminate the potential information included in a verbal description of a graphic depends in part on the conventions for interpreting documents in a specific fields of study (e.g. meteorology, geology). In many cases, however, some information such as color, texture or even values can be eliminated from the description of a diagram because it only reinforces, rather than adds, information central to the meaning of an image. You can keep your description succinct by including only the information absolutely necessary to interpret the image. A key question to ask yourself is whether or not a sighted reader will gain additional information from your description that an audio reader will not. If so, then eliminate or adapt different elements of your description.

Effective Description

After an initial analysis of your informational image, you need to consider exactly what the purpose of that image is in the context of its presentation. In addition, consider which of its features (elements, data, drawings, etc.) provide the most explanatory power in communicating your intended meaning.

Charts & Graphs

Charts (pie & map) and graphs are one of the most commonly used information formats to illustrate proportion and distribution of data. Charts and graphs are actually among the easiest of informational images to make accessible through textual description and don't always require a content expert to develop. We'll examine two methods, one more suited to being created by the content expert than the other (see Option 1 below).

How would you describe a chart/graph effectively? Consider the criteria needed for the effective description and interpretation of informational images.

1. Identify the purpose of the chart. What kinds of data and relationships is it supposed to communicate to the viewer? Does your chart's heading communicate that purpose?
2. Determine which specific pieces of information are the most significant. Those are the elements to which you need to first direct the viewer/reader's attention. We report data to communicate ideas such as growth, decline, distribution and other cause-effect relationships. Consider what it is you are trying to achieve in communicating this data to your intended audience.
3. In what order would you present that information-declining in significance from most to least-so the viewer best comprehends what is being communicated? When managing variables such as:
   1. Number and titles of categories represented (sets of data, time, space, etc.)
   2. Media used to convey significance (color, labels, texture)
   3. Relationships represented
      1. Distribution
      2. Cause-effect

It generally enhances the clarity of your description and chance of the viewer/reader understanding your intended meaning if you begin by explaining the relationships represented. A brief explanation of the relationships provides a kind of "frame" for the subsequent information (categories, media) you describe and thus makes an accurate interpretation of the image likelier. As with "the bigger picture" to which we might refer when piecing together a puzzle, viewers/readers are able to better place the specific pieces correctly if they comprehend the various relationships in terms of the "frame."

Exercise A--How would you describe this image effectively?

1. The purpose of these two pie charts is to provide quick evidence of the changes in Lantapan's agriculture-based economy.

2. The easiest way to make the significant information accessible is to literally identify the resources and associated percentages on each chart, as illustrated in Option 1. Another approach, explained in Option 2, might begin by summarize the most essential relationship being identified by the data presented in the chart-the differences in each category over time.

   

   Because such data is generally available in other documents in text form, this is an easy method. There are two disadvantages to it, however. The first is that there is simply a lot of text. A second issue is that a person using a screen reader will have difficulty telling which percentages go with which category unless they listen carefully to the structure of the list, focusing special attention on your use of punctuation (the semi-colon in this case), which generally serves as a cue for association.

3. Consider the order in which you present information. A second option is to highlight the differences in resource categories over the years based on their significance, as shown in Option 2. The advantage of this is that the "need to know" information is highlighted, as well as the significance of the information to the designer's message: Lantapan is developing. This method's primary disadvantage is that is may take a little more time to develop a succinct description than simply list the pre-existing information on a chart.

Diagrams

Another commonly used type of informational image is the diagram. Diagrams tend rely more on pictorial images than charts & graphs, which usually are used to represent data. Diagrams often contain more abstract content than charts and graphs.

One of the most common issues with diagrams is that they provide an abundance of often unnecessary information to the reader/viewer-it's easy to assume "more is better" when it comes to communicating information. Such abundance may actually interfere with the reader/viewer comprehension of information, however, and diminish the clarity of the message the designer of the diagram intends to communicate.

How would you describe a diagram effectively? Consider the criteria for effective description and interpretation of images.

1. Identify the purpose of the diagram. What is it supposed to communicate to the viewer?

2. Determine which specific pieces of information are the most significant. What information -at a minimum-does the viewer absolutely need to know to understand the concept, process or object being communicated? These are the elements to which you need to first direct the viewer/reader's attention.

In what order would you present that information-declining in significance from most to least-so the viewer best comprehends what is being communicated? When managing variables such as:

a. Labels & titles of items represented
b. Function diagram serves or Idea diagram conveys
c. Media used to convey significance (color, labels, texture)
d. Relationships represented

i Logical explanation

ii. Cause-effect relationships

Think about which types of information you could leave out.

Exercise B--How would you describe this image effectively?

1. The purpose of this diagram is to provide an explanation of the different components (body parts, chemicals, etc.) used in the process of digesting food. Note it is quite complex, relying upon labels, spatial arrangement, arrows and color to communicate the process to viewers.
2. Assessing which of these components make up the most significant information involves examining the process as a whole before identifying which communicative markers or media (space, color) should be included or left out of the diagram's description. In this case, the need-to-know information includes the body parts and chemicals, their role in digestion and the order in which each is involved in the digestive process.
3. The order in which that information is best articulated is made challenging here by the fact that there are several processes involved with digestion, resulting in a multi- rather than uni-linear path depicted in the diagram. In determining which pieces of information can be left out, it seems clear that while the names of each component are necessary to a description, their spatial layout as depicted on the diagram is not. Similarly, as long as the relationship and role of each component is explained in a logical, cause-effect order, descriptions of the color used to depict them in the diagram are unnecessary.

Clearly there is good reason to be concerned about charts, graphs and diagrams that appear in PDF or PowerPoint presentations, for once published to the Web, the supposedly "easy" conversion of those documents into HTML fails to make them accessible to many users. But by assessing whether you already have the necessary information available, need the assistance of your local services for disabled students or can reduce the volume of information needed in your images, you can save a lot of time when developing effective descriptions.

In summary, remember that the effective description of charts, graphs and diagrams involves:

1. communicating the purpose of your image
2. determining which pieces of information are the most significant to achieving your purpose
3. establishing a logical, user-oriented order to the information you communicate through your images.

Remember that it is the content exper that is in the best position to determine these criteria and develop an effective description to accompany the informational images you use so they are accessible to all.

Go back to top.

Go back to Tutorial's page.