Originally posted by the Cartographic Design Team on the Ordnance Survey blog.
We’ve been taking a closer look at each of our Cartographic Design Principles in turn and this week we are delving deeper into A clear visual hierarchy. Although we consider all eight of our principles to be of equal importance when designing a map, this one is of key concern to the successful communication of a maps message. Without a clear visual hierarchy, a map can be confusing to the user and may lead to poor decision making.
Clear visual hierarchy
The aim here is to draw attention to certain elements of the map and push those of less importance further down the visual plane – although certain features are less important they may still be required, if not then they should be removed. This helps the user differentiate between map features and helps them comprehend the maps message effectively.
The concept of figure-ground is key as it helps the user to distinguish between the main focus of the map (figure) and that which is background or contextual information (ground). The required contrast can be achieved using various methods:
- colour – hue, saturation, brightness, temperature
- texture or pattern
- proximity – how far away map features are from one another
- graphical effects – such as drop shadow and outer glow
- text – font, weight, style
Jacques Bertin’s Visual Variables
Jacque Bertin was a French cartographer who is famed for his book Semiology of Graphics which was originally published in 1967. When developing our principles, Bertin was one of the people whose work we referred to. It is widely regarded that his work represents the first attempt to provide a theoretical foundation to information visualisation, based on his own knowledge and experience in the field of cartography.
He introduced seven visual variables which refer to the differences in map elements that are perceived by the human eye and these are fundamental to achieving a good visual hierarchy. This set of visual techniques has had a positive impact on many cartographers’ design decisions and Bertin’s influence can be seen across the many disciplines of design. This is a great article about visual hierarchy in web design which has its own take on Bertin’s visual variables.