At the recent 2014 Geo Open Source Conference in Philadelphia hosted by GeoPhilly and LocationTech, James Tyack gave an excellent presentation on building applications for accessibility. He demonstrated UnlockPhilly, an app that identifies accessible transit stops and the businesses near by. You can hear James’ full talk here.
This momentum around accessibility got me thinking more about how we, as mapmakers, can keep in mind individuals with visual impairment including low vision and color blindness. I first wanted to explore some of the current solutions available.
Mapping for the Blind: Printed Materials
The first time I came across a tactile map was in a Patco Transit Station. This thoughtful map has unique textured features for routes and braille text for each stop name. According to Patco’s Twitter account, this particular map was created by Visual Marketing System, Inc. I was impressed with how legible it was and how simply it communicated the different routes and stop types (both with color and tactile symbols).
For geographic locations that do not yet have tactile maps available, LightHouse, an organization based in San Francisco, provides a service to create tactile maps of parks, transit systems and street maps. The raised features and simplified enlarged text can be suitable for individuals who are blind or have low vision. The technology used in printing is known as Tactile Map Automated Production (TMAP) and was developed by Dr. Joshua A. Miele, a scientist at the Smith Kettlewell Eye Research Institute.
Navigation for the Blind
Screen readers allow individuals with visual impairment to interact with websites on desktop or mobile devices. These do not normally work well with maps. OSM (OpenStreetMap) for the Blind has assembled many resources for individuals needing different methods to interact with web maps including Look and Listen Map, an interactive audio book atlas.
Additionally, Blindmaps is prototyping a device that integrates with white canes for navigation and spatial awareness. It also integrates technology from Blindsquare, a popular iphone app that provides audio context based on GPS coordinates and integrates with FourSquare for points of interest and OpenStreetMap for navigation.
Accessibility for Color Selection
As mapmakers, we might not have the tools to develop innovative solutions like the ones described above. But one thing we can do to make web and print maps more accessible is to make more thoughtful palette choices to accommodate people with color blindness. I started this conversation when recommending cartography design for accessibility as one of the 4 Color Cartography Tips Hue Should Know. I’d invite you to explore a fantastic blog post written by John Nelson on the subject called Charting for Understanding, about the color spectrum and important considerations when communicating with color. He makes uses of a chart as an example and recommends using additional techniques to help show variations in data. He also mentions reconsidering how the data is displayed, in his example, he rotates the chart and aligns the point of neutrality of each country survey to make the variation more clear. John also mentioned Vischeck, a tool that can be used online or on a desktop computer to verify sufficient color differentiation for vision impairment. Below you can see how this tool identifies color disambiguation.
As you can see, in the first image the tool identified the ambiguity in colors for individuals with color blindness. The chart in the second version is corrected and the colors can now be differentiated.
Vision Accessibility & Map Design
When symbolizing diverging data, use ColorBrewer’s color palettes that are defined as color blindness safe which can ensure these are appropriate for most users. Colorbrewer helps you avoid selecting color schemes with too little variation or too many conflicting colors that can be confusing.
When selecting color for background features on your map, keep variation and contrast minimal. This will help guarantee that the features on your map will be the focus of your design. Keep in mind there are many types of color blindness and vision impairment. It is always helpful to use Vischeck to validate your map because even if you use a safe palette, other colors in your design might interfere with communication. When all else fails, especially for print, consider a single color ramp or black to white ramp. Remember that communication is more than just color: consider using simple textures or recognizable symbols to increase readability.
When selecting fonts for an accessible map, keep it simple: avoid serifs (fonts with curly text), decorative or italic fonts which can be difficult to discern even among people with perfect vision. For more fantastic tips on accessible map design, consult Apollo Mapping’s excellent two part blog on color blindness.
Pretty cartography is not always accessible cartography. Keep it simple, and always run a draft of your print map (or a screenshot of your web map) through a color validator to ensure accessibility, or if possible, consult someone with vision impairments on the legibility of your map before it’s put into production.