Meaningful Images and GIS
By Victor Chakravarty and Paul Sandlin
It is widely held that Geographic Information Systems (GIS) applications are exempt from State accessibility requirements. This is not true! It is true that State policy does offer some relief in the presentation of certain types of images. However, the applications that present these images are fully subject to State accessibility policy. In fact, the issues surrounding the images themselves are very complex and their accessibility requirements are only eased and not exempted. Those developing image intensive applications need to understand the subtleties in this area.
Defining the scope of the discussion, we are talking about applications that deliver what are known as meaningful images. Meaningful images are images that convey more information than can appropriately be expressed as alternate text. Put another way, a meaningful image is one that has significant interpretive elements that represent the primary information being conveyed. This category includes images such as maps, some graphs and artwork.
State accessibility policy requires that images must be accompanied by “alternative text” descriptions so that the information contained in the image can be mined by those using assistive technology. In the case of meaningful images this requirement is relaxed. State policy bows to the reality that certain images, either because of their complexity or subjectivity, cannot be fully described in text. It is important to note that this should not be interpreted as a free pass. Alternative text descriptions are still required, it is only the comprehensiveness of their description that is eased.
One might ask “Why bother with the textual description at all if it is impossible to express images’ complex meanings?”. The answer is that even a rudimentary description is helpful in providing context to a person without direct access to the image. This context is helpful both as a signpost of a potential navigational black hole and as a means of informing them of what they are not getting. The latter might seem strange but it is important to remember that the burden of equal access for services is not lifted through the relaxation of the alternative text requirement. It is merely transferred away from the technology solution to the operational area sponsoring the service in the first place.
So, what are the top three tips that we can offer to the GIS application developer in order to surmount this challenge? Here they are:
- Make full use of the ALT IMG tag. This is absolutely straightforward when it comes to static maps, yet is often left unpopulated. From this point onward, whenever you code a static map, please ensure that the ALT IMG tag is populated with an appropriate descriptor.
- Extend the same paradigm to dynamic maps. It's a little more complicated than doing it for static maps, but still very much achievable. What you need to do is to splice the dynamic selection criteria into some pre-set verbiage. When you are getting started, the resulting output may sometimes stretch the rules of grammar, but nevertheless, it will open up your maps to more people than ever before.
- Make full use of the mouse-over text. Cram as much contextual text, otherwise embedded inside the map, into the mouse-over text as possible.
Of course, this is not an exhaustive list. But we think that these three will get you started in terms of thinking and acting upon Accessibility when it comes to GIS Applications.
The State of Maine is heavily invested in the ESRI toolset for its GIS Applications. The good news is that ESRI is fully committed to Section 508 of the U.S. Rehabilitation Act of 1973, which happens to be the bedrock of all Accessibility statutes in this country. (See, for example, http://www.esri.com/software/section508/position.html .) Even though the Maine State Accessibility requirements exceed those of Section 508, it's nevertheless a great starting point. The next piece of good news is that Maine OIT maintains a rich Accessibility portal at http://www.maine.gov/oit/accessibility . We urge all GIS application developers to avail themselves of the contents of this Accessibility portal.
Best of luck!
Questions and comments to Victor Chakravarty or Paul Sandlin