There is a genetic disorder that affects up to 10% of men and about 0.5% of women. It impacts on their daily lives, often making the simple everyday tasks difficult and crushes the dreams of budding pilots and wannabe coast guards everywhere. Yes, it’s colour blindness. But for something that is experienced by a sizable minority of the population, colour blindness seems to play a relatively small role in the design process. Think weather forecasts, snooker and, yes, maps. The traditional rainbow of cartographic colours – greens for vegetation, reds for main roads and footpaths, and blue for motorways and rivers – can become indistinguishable, therefore making map reading really difficult.
It’s an issue that has been looked into by others, but up until recently it’s not something that we have been able to take into account when producing either our paper maps or our data. But all that has changed in recent times. With the launch of customisable data, like OS VectorMap Local, the user has far greater flexibility around how mapping is displayed and styled.
Colour blindness is the result of a deficiency of the specialised ‘cone’ cells in the eye that make colour vision possible. It is the most common genetic disorder among humans, with hundreds of thousands of people unable to tell the difference between reds and greens. Instead these colours appear as shades of grey or brown, making it difficulty to interpret colour-coded features. The Product and Cartographic Design teams here at Ordnance Survey have been working on colour schemes that can counteract this effect.
One of the styling exercises specifically for the colour blind, looks strange as it uses completely different colours for familiar map features. The result is a combination of purples, browns and oranges.
Simon Duquénoy, Technical Product Manager says:
“Cartography is a fine art, but the colours that have become so familiar to most of us are actually among the worst possible choices for those with colour blindness. Because of the technical developments in mapping data, we’ve been experimenting looking at how we can be more colour-blind friendly in our designs and colour choices.”
We are now developing a new colour palette for mapping that will work whether you are colour blind or not. This has been designed using software that can emulate the more extreme forms of the impairment. It has also been tested with a group of colour blind test pilots drawn from Ordnance Survey staff. While initially using the science of colour differentiation, we soon ran into familiarity issues – ‘Why is the motorway red ?’ asked the test group for example. Due to this we revised the colour style to make motorways blue again, but using a different shade to provide the contrast with other colours that is so important to the colour blind.
This is a major leap forward in cartographic design and leads us from thinking about specific accessibility for those with hidden impairments, to maps that are really usable by everyone.