Symbology
When producing maps it is important for the data to be represented in a clear way that the user can understand. The symbols or icons should be representative of the data being shown. A map should not show too much information and only used the data that is going to support the overall theme of the map. Too much information may make the map confusing to the user.
Colour considerations and cautions
Colour blindness – this is quite a common problem. Most people with colour-vision deficiency have difficulty distinguishing between red and green. ‘Red-green’ deficiency affects one in 12 men and one in 200 women globally and can make it hard for them to tell the difference between reds, oranges, yellows, browns and greens. They may also have difficulty distinguishing between shades of purple and may not be able to tell red from black. ‘Blue-yellow’ deficiency – affecting vision of blues, greens and yellows – is another form of colour blindness that is much rarer. This Brilliant Maps blog explores what maps look like to people with colour-vision deficiency.
Format, use and context – colours look different on screen compared to paper, so the ways in which a map is distributed and used should affect colour choice. If a map is intended to be desktop printed, questions around the quality and availability of printers and inks arise. If a colour map is printed in black and white, will it still be fit for purpose? If a map is shown via a projector, will details be visible?
Cultural significances – colours have different meanings and associations in different parts of the world. For example, in some cultures, death is associated with black; in others, with white. Red can be associated with danger, good fortune or grief and death, among other things, depending on where you are. This is one good reason why team diversity, as well as awareness of and consideration for different cultures, is important in mapping – as elsewhere in life.
Resources
The following two examples are tools that can help in representing data in a clear way.
Humanitarian icons
The United Nations Office for the Coordination of Humanitarian affairs (OCHA). MapAction has supported in the creation of the various GIS ready formats for ESRI (ArcMap and ArcGIS Pro) and QGIS.
ColorBrewer
This is a tool that can help in the use of colour in a map particularly in choropleth maps where colours are used to represent a classified data. In these maps it is recommended not to use more that six classifications as if it is more than that then it is harder to distinguish by the human eye. The ColorBrewer tools allows the map creator to test different colour palettes for different classifications but also making sure that they are colour blind and photocopy friendly.
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