High-contrast mapping

In this post I will use the example of some work I did back in May 2015 when I was tasked with creating a new location map or ‘How to Find Us’ map for OS.

Firstly I use the term high-contrast to mean a large difference between overlay (figure) and base (ground). This is not to be confused with the image contrast of the overall map which is likely to be quite low due to the paper space of the overlay being far smaller than that of the base.

A previous version of the 'main' map © Ordnance Survey
A previous version of the ‘main’ map
© Ordnance Survey

The map was actually not one but a set of maps to be published within a brief guide. Three different scales of map had previously been shown: a regional overview, a main map showing our location along with classified roads in the area and the central railway station (above), and a detailed ‘OS MasterMap’ plan of the entrance and car parks.

My main task was to revisit each scale to make each more usable and more defined and to make the 3 maps work together to be more consistent and with a new look for a new guide.

Researching other maps of each size, type and use I quickly formulated a new plan. Sadly I do not have the original maps and plans that were my inspiration at the time but they were a mixture of civil engineering drawings, site plans, transport and route maps. I seem to recall a bike map from the US being a catalyst but looking at other maps is always a great starting point for any cartographic project.

The kind of inspiration used. Credit and assumed copyright:  WRT, Ocean Park, DS+R, Washington Post
The kind of inspiration used
Credit and assumed copyright: WRT, Ocean Park, DS+R, Washington Post

The main map used to be a network of ‘A’ roads covering the western half of Southampton. I once again decided to make the geographic extent smaller but looking at modern site plans and cycle route maps or visualisations gave me the belief that I could show far more detail whilst making it look like less and be easier to read and mentally route along. The idea of high contrast maps was born – at least in my head.

My idea was to have a very washed-out basemap but with enough visual hierarchy to show the area in good topographic detail. By keeping all of these features so low down the visual plane (the entire base map is above 75% lightness, or 87% excluding labels), I was able to create a very large difference in contrast between the base mapping and the overlying subject matter (at less than 50% lightness).

Note: Colours should really be compared by luminance for a visual hierarchy as my previous paper poster at ICC2013 demonstrated. A good explanation is on offer here but for the purpose of this post ‘lightness’ as used by LAB colour is easier to show the principle.

The black labels along with the deep turquoise of the OS head office and its label stand out so much so that your eyes are immediately drawn to this information. The point being that in a location map with written descriptions of ‘how to get there’, this is really all you need plus a little bit of context. The subtle detail is in no way distracting yet is visible enough to link each prominent piece of information together.

© Crown copyright and/or data rights 2016 OS
© Crown copyright and/or database right 2016 OS

The more you look at the map, the more you discover but like a map is supposed to, the important message is seen first. Some cartographers might argue that unnecessary information should not be shown on a map but our own principle states that features without value to the user should not be shown. Although I believe high contrast maps are suitable for a relatively small amount of situations, I firmly believe that on this occasion I have shown only useful data and that I have created a hierarchy that is far more usable than a more traditional location map with less detail.

The regional overview would cover a smaller geographic extent than it did previously and focus on the main road and public transport connections to link in with the ‘by car’, ‘by train’, ‘from the airport’ style of the accompanying text. So the plan here was to show a minimal number of key roads and make the public transport information the dominant map subject. This is where the high contrast worked really well and resulted in a very clear thematic map of public transport but with enough context given by the roads and water. To tie the maps in better with the new OS brand colours, I did change the colours accordingly and sacrifice a little of the contrast but I feel the map still works well.

© Crown copyright and/or data rights 2016 OS
© Crown copyright and/or database right 2016 OS

Finally, for the ‘on arrival’ map I brought the previous two maps together in terms of style and content but at a far more detailed (larger) scale. The base map style is identical to the main map for consistency allowing the user to orientate themselves within the map and for the same reason the same shape building footprint is used on both maps. The walking route from the bus stop to the entrance (red) and the on-road route to the visitors car park (blue) are both stand-out features, and the importance of the OS building (Explorer House) has been shown without dominating the map entirely by changing the solid deep turquoise fill to what looks like a 3D model of the building. This model is in fact just OS aerial imagery of the building clipped to the previous footprint.

© Crown copyright and/or data rights 2016 OS
© Crown copyright and/or database right 2016 OS

The different elements are brought together with the text by our creative designers to create the published guide.

© Crown copyright and/or database right 2016 OS
© Crown copyright and/or database rights 2016 OS

I actually produced an even higher contrast version to begin with (seen above) which I do actually still prefer but I wasn’t able to convince the business which I can understand as the base is very subtle, might get lost on some monitors and this idea of high contrast mapping is something that is far from the mainstream of mapping that people seem to have accepted as the norm. It does however show that even in basic cartography we can still be adventurous and strive for new ideas and to push the boundaries (of what is considered to be the correct way of doing things) in order to create more effective communication.


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