Cartographic Design Principles: Legibility

We are just over halfway through our series of posts about our Cartographic Design Principles. Last week we shone the spotlight on Simplicity and this week we continue our series as we turn our attention to Legibility. In its simplest definition, to be legible is to be easily read. It is extremely important for a map to be legible as the user should be able to easily understand the message that the cartographer was attempting to portray. Much in the same way as a book, if a map is difficult to read then it is likely to fail in its objective and not meet the user requirements.


OS Explorer Maps – designed for usability and legibility 


All map elements need to be legible, meaning that they are readable, understandable and recognisable. All need to be large enough and clear enough relative to the viewing scale and the media on which the final map will be displayed.

Legibility of most map features depends on colour and size which ultimately make them noticeable and recognisable. Symbols need to be simple enough to recognise and offer good contrast against the background.

Text can be made legible with a good choice of font, good colour contrast against the background, suitable font size, character spacing and the use of masks or halos. Like any other map feature text can also be made more recognisable by choosing a representative colour, for example, blue text is immediately recognised as being related to water.

The proximity of map elements to each other is also important to the overall legibility. Overlapping symbols and text should be avoided where possible in order to make the information clear to the user.

To achieve legibility a process of cartographic generalisation is often required – this can take many forms; from simplification to amalgamation and will be dependant on the scale and use of the map.

Typography for cartography

Highly-esteemed Swiss cartographer Eduard Imhof was famed for his fantastic work on shaded relief maps. He also wrote a set of four principles regarding the placement of labels on a map, the first of which was, “names should be legible”.

Legibility is a key, and much covered topic in the world of typography and text is a fundamental element of most maps. This article covers some of the basics of typography in cartography, explores some of the decisions a cartographer must make and discusses legibility in detail:

Typography for Cartography can be more complex than traditional typography because of complex text placement and potential density of features, visual hierarchy, overall look and feel, the fact that text often represent features as symbols in their own right, and the interplay between text and other multi-layered map features such as symbols, background colors, and textures. However, the overall goal of legibility and readability remains the same.

This shows that a cartographer has many decisions to make during the map creation process and demonstrates how all the principles must be considered simultaneously.

Next week, in the fifth part of this series, we will focus on consistency in map-making.

2 Responses

  1. Ken Shorey

    On OS Explorer maps, most place names are in a ‘sans serif’ font (Univers?) but a few (eg. Topsham, Devon) are in a different ‘with serif’ font (Times New Roman?). Why is that? My guess is that it’s something in their history, perhaps a mention in the Domesday Book.

    1. Hi Ken

      I’ve just checked with our Customer Service team and it’s actually just down to the different map specifications we’ve had over time. There are lots of fonts that fall into the serif category and the varying text on our mapping relates to the specification at the time that the mapping areas were updated. As the specification changes any new text labels will be added accordingly, but it is not viable to update all the existing text labels for the mapping when the spec changes, this is why there are lots of different types of font shown on the mapping.

      Many thanks

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