Colourblind mapping
Ordnance Survey has created two new maps for people with colour vision deficiency
It’s not something most of us need to think about when we reach for a map – whether or not the colours will send us astray. But for people with colour vision deficiency (also known as CVD or colourblindness), it can be an issue. These problems prompted cartographers at the Ordnance Survey (OS) to create two new types of map for those suffering from the two most common forms of colourblindness – red-green and blue-yellow.
‘It’s something that’s quite often overlooked in the map-making industry. A lot of the time, rainbow colour schemes are used and they are really not very accessible,’ says Jessica Baker, who led the project. ‘As OS is the national mapping agency of Great Britain, we wanted to set a precedent and lead the way in championing accessibility and championing prioritising colorblindness.’
The different types of CVD presented different challenges. People with the red-green type may find it difficult to tell the difference between reds, oranges, yellows, browns and greens, or they might see these colours as much duller than they would appear to someone with normal vision. Those suffering from the blue-yellow form commonly find it difficult to distinguish between blue and green, and between yellow and red. Red-green
CVD affects around one in 12 men and one in
200 women, while blue-yellow is much rarer. True colourblindness, where someone can’t see in colour at all, is rarer still, although it does exist.
After researching CVD and consulting sufferers, the OS team realised that the best solution was to tweak the contrast and shade of the current colours, rather than starting from scratch with new colours. ‘It was things such as motorways, waterways, green spaces,’ Baker says. ‘They all appear as quite similar shades of green on OS maps at the moment. We made them a little bit more contrasted so it was more clear, and we also changed the colour of the text to make that black or a darker shade.’
The end result was two different maps aimed at people with the two types of CVD. ‘We then found that if they worked for those people, generally they would work for people who have monochromatic vision, which is a very small percentage of population,’ Baker said.
The new maps are being rolled out on Zoom Stack, OS’s customisable basemap of Great Britain, which works at any scale. The plan is now to extend them to other OS products and the OS app.