Accessible Data Visualization and Digital Mapping
Amanda Tickner GIS Librarian MSU Libraries
Accessible Learning Conference 2019 MSU
World Wide Web Consortium (W3C) Web Accessibility Initiative (WAI) produced the WCAG guidelines
The Web Content Accessibility Guidelines, also known as WCAG (1.0), has been around since May 5th of 1999. 2.0 has been around since 2008, and 2.1 has been around since 2017.
1.4.13Content on Hover or Focus
Level AA(Added in 2.1)
Where receiving and then removing pointer hover or keyboard focus triggers additional content to become visible and then hidden, the following are true: Hide full description
Dismissable: A mechanism is available to dismiss the additional content without moving pointer hover or keyboard focus, unless the additional content communicates an input error or does not obscure or replace other content;
Hoverable: If pointer hover can trigger the additional content, then the pointer can be moved over the additional content without the additional content disappearing;
Persistent: The additional content remains visible until the hover or focus trigger is removed, the user dismisses it, or its information is no longer valid.
How implementable is this? Colors don’t map effectively into RGB space, and they don’t give RBG equivalents. Mostly focused in instrument data, implementing into specific programs rather than general applicability.
WCAG 2 level AA requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text, and a contrast ratio of at least 3:1 for graphics and user interface components (such as form input borders). Level AAA requires a contrast ratio of at least 7:1 for normal text and 4.5:1 for large text.
Instead of thinking of foreground/background, think of elements of the map or data visualization to compare between parts of the graphic.
Compare “plain” bar chart to a circular bar chart, talk about clarity and parsing information
If one color is darker than another - it looks bigger...
Embedded text = problem
Categories are distinct, 30% different, but background is an issue
Go back to the last slide and think about alt text - pose the question
This helps us distill why we are creating a data visualization, and what it is depicting. Sometimes people put things in publications unthinkingly.
Example: discussion with colleagues where they thought lat/long of a map was an acceptable description in alt text… nobody thinks like that
This is really turning data into art, in a sense