Anyone with colour vision deficiency (CVD) will know the problem when confronted with reading a traditional map; they are much more difficult to read than they should be. Colours usually easily distinguishable to the human eye, such as red or green, appear very similar and maps that use spectral rainbow colour schemes are difficult to comprehend.
Ordnance Survey (OS) is working to solve these issues by experimenting with alternative mapping styles for people with CVD. It has developed free styles to download for digital mapping, through its customisable mapping tool OS Open Zoomstack (www.ordnancesurvey.co.uk/business-government/products/open-zoomstack).
OS data scientist Jessica Baker created two new mapping styles; one to help red-green colour blindness and one to help blue-yellow.
‘Colour blindness comes in several forms,’ says Baker. ‘Meaning one colour scheme is unlikely to be suitable for all colour-blind people. The most common form – red-green blindness, also known as deuteranopia and protanopia, affects around 8% of men and 0.4% of women. The gender imbalance is caused by the number of X chromosomes in men compared to women.
A visual representation of different forms of CVD
‘People with this form of CVD have trouble telling red and green hues apart. Blue-yellow blindness (tritanopia) is much less common, affecting fewer than 1% of men and women. This condition makes it hard to distinguish between blue and green colours, as well as yellow and reds. Although this may seem like a small portion of the population, online maps are likely to reach tens of thousands of people with CVD.
‘We know that people depend on OS data and wanted to maximise accessibility and ease of use both for people with CVD, and those without. I created these styles with both groups in mind. We’ve made changes to the traditional styles we all know and love that will work much better for colour blind people.’
The process began by assessing different map layers which can be easily confused. Notable mix-ups included woodland and greenspace, and motorways and waterways.
‘I tested several colourways alongside colour-blind colleagues as I’m not colour blind myself,’ says Baker. ‘It was really enlightening to see how OS products can be made more CVD-friendly. I found that increasing the contrast between layers worked well, as distinguishing between different contrasts of the same hue is something that those with CVD tend to manage.’
After this analysis and internal testing, OS created its first versions of the two new CVD-friendly styles.
The new styles can be downloaded for OS Open Zoomstack, an open data map of Great Britain. This is a free digital tool available for anyone who wishes to use geospatial data to create mapping for apps, websites or offline. Users take a giant vector basemap of Great Britain, containing up-to-date authoritative OS data, and produce their own maps quickly and easily in a style of their own choosing.
‘Developing these initial styles is a real push forward for accessible digital mapping,’ Baker adds. ‘Please let us know what you think of the new styles – whether you are colour blind or not. We’re keen to know what you think so that we can continue to improve the quality and accessibility of our data.’
David Jones is a media executive at Ordnance Survey.
• To send feedback or for further details of the project contact cartodesign@os.uk.
