Colour blind cartography

Question

Depending on what you read, 7 to 15% of the general population has some form of colour blindness. That's a significant amount of people. Do you try to account for this in your map designs? If so, how? Do you handle digital map design differently from hardcopy? Any indispensable resources?

Answer 1

One of my clients is colour blind, and when I make maps for him, I use vischeck.com to check my work. You can upload your own image, and it will return a processed version of it that shows what it will look like to colour blind folks.

It has options for various types of colour blindness, and is pretty educational to boot.

Answer 2

The large majority of the work I do is for a very limited audience, so no, I do not usually account for colorblindness. If you do need to accommodate colorblindness, color brewer has a "colorblind safe" option that is helpful.

Answer 3

I am slightly red-green colourblind (in that I can still see red and green fine, but have difficulty with say a red and green line next to each other). Does make it a bit easier for me to make maps for people that are red-green colourblind.

In addition to color brewer and vischeck mentioned above, the GIMP has colourblind filters built in so you can adjust images as part of post processing. Photoshop has the same kinds of filters if you have access.

Lastly the ESRI Mapping centre has a set of styles for download that include a colour set suitable for colour deficiency.

Hope that helps!

Answer 4

This is a very good topic.... and there is software out there for cartographers.

Color Oracle is a colorblindness simulator for Window, Mac and Linux

http://colororacle.cartography.ch/index.html

The system-wide menu quickly converts your art into a palette that simulates what colorblind people see.

Covers different aspects of colorblindness

Deuteranopia, protanopia and tritanopia.

"Designing maps for the colour-vision impaired" [PDF]

http://colororacle.cartography.ch/design.html

Answer 5

Gretchen Peterson has written a few books/booklets on GIS cartography that could be useful resources.

• GIS Cartography: A Guide to Effective Map Design
• Making and Using the Colors For Maps Booklet - Includes a colorblind sample of each colorscheme.

She also references the website:

• ColorSchemeDesigner - which has an interactive visualizer that emulates what a colorblind (many varieties available) user would see.

Answer 6

A new about Ordnance Survey work about color blind maps http://www.wired.co.uk/news/archive/2011-05/11/ordnance-survey-cvd-maps

Answer 7

we were exploring this topic and produced a draft document (link below) which maybe of use...I would appreciate any feedback you have to improve this document

https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0BymNZZfQQ3a0NjQxOGVmMjYtNzE5NS00ZGI1LTg4NDMtZTFkYTg0NDQ1YmVi&hl=en&authkey=CJmi15oE

--- ADDENDUM ---

As requested here are the main tips...a lot of them are also listed in other peoples responses.

Tips for making maps for colour-blind people

1. Exaggerate lightness differences between foreground and background colours. Avoid using colours of similar lightness adjacent to one another, even if the hue or saturation is different.

2. Minimise the number of colours used in thematic maps.

3. Use a colour scheme recommended at http://colorbrewer2.org/ such as one of the diverging schemes above. They have schemes recommended for color blind use.

4. Vary the lightness of the colours used. The intensity differences visible for persons who are colour-blind.

5. Use thicker lines so the eye can interpret the colour better.

6. Where possible, make stylised maps with less geographical information. The reduced information means there are fewer colours to distinguish.

7. Use white halos around lines as this helps keeping the colours distinct and reduces the confusion when the lines intersect.

   • Install http://colororacle.cartography.ch/ which allows you to change the whole display to the 3 main types of colour blindness to check if the scheme used is ok.
   • Check http://colororacle.cartography.ch/links.html for other software that can be used.
   • Read http://jenny.cartography.ch/pdf/2007_JennyKelso_DesigningMapsForTheColourVisionImpaired.pdf
   • The Conservation template project is addressing this same problem for a different reason: If you are using a basemap with a colour scheme then the thematic map you design to lay over that basemap cannot use those same colors. In looking at the maximum information you can carry without relying on colour we are spending time looking at symbol texture and pattern, using similar methods from black & white photo-interpretation. These line symbols only work well within a limited scale range, in this case 20k to 1k. Then you have to shift to a different set. They all rely on the line offset and layer properties to create the 3 bands, but that technique may not scale well in dynamic feature services so if we can find a design that works we may look at other server options like caching. Charles Convis, ESRI Conservation Program Coordinator.

Answer 8

Some more general resources for online work are the W3C's Web Accessibility Initiative, an implementation of a Contrast Analyzer, and The Shaw Trust's Web Accessibility Services.

Answer 9

Fairly old question, but as I'm horribly colourblind myself, I'll throw in my 2¢...

A quick and dirty method is to print the map out in greyscale. If you can't tell the difference between two shades (and they're similarish colours on the coloured map), then I (and, I assume, other colourblind users) may not be able to distinguish between them on the coloured map.

Answer 10

User colorbrewer from http://colorbrewer2.org/. They have options to choose colorblind safe images.

Answer 11

There is a good article in Cartographic Perspectives:

Color Design for the Color Vision Impaired, Bernhard Jenny and Nathaniel Vaughn Kelso

There is quite a lot of theoretical considerations and practical tips. It utilizes Color Oracle tool mentioned by GeorgeC.