Information display

Map and reality: diagrams

In the previous two parts, we’ve figured out that the preferred distortion and layers depend on the map’s supposed use case.

With public transport maps, our goal is to help the customer get from point A to point B using the displayed transport network.

This is a map of Paris Metro of 1915:

Paris Metro, 1915

The city is shown in full detail. There are many layers. The metro lines, however, stand out because of the use of contrasting red thick lines.

Compare with the map of London underground railways of 1908:

London underground railways, 1908

The lines of different railways are denoted by different colours. The rest of the city — the roads, the parks and the river — makes one pale-gray layer.

But even this layer is removed by 1932:

London underground railways, 1932

The river Thames is the only non-railway object that remains on this map. And it is the only device that links the railways to the surface geography.

It is always interesting to explore a detailed map with lots of layers. But in this case, the pleasure of exploration is much less important than the customers’ ability to quickly pick out which train to take. The information richness is sacrificed to the comprehension speed.

But as we see, despite all the simplifications, the central part is still rather hard to read. In several places, arrows had to be used to clarify the correspondence of labels and stations.

The engineer Henry Beck has come up with a radical idea. He suggested redesigning the maps using the principles of electrical circuit drawings.

Electrical circuit

Such drawings prioritise the logical connection between the elements over their physical position. What if a railway map also displayed first and foremost the logical connection between the stations?

The Beck’s diagram has replaced the map in 1933:

Beck’s Underground map, 1933

All lines segments were put to the angles of 45° and 90°. The distances between stations were equalised.

The modern diagram has twice as many lines and many more layers, but it inherits the Beck’s principles:

Modern London Underground map

Compare with a geographical map of the same lines:

Geographical London Underground map

The central part here is so dense that it had to be put in a cutaway at a bigger scale. And even so, everything turned out very small. Now we see that showing “true” geography is not universally useful. This geographical map is much harder to read. For the railways' customers, the diagram excels.

If the distances between the stations are equal, the reader will grasp that it’s just a convention and won’t rely on it. If the lines are strictly at 45° or 90°, the reader will grasp that they do not represent the actual paths of the underground tracks and won’t rely on it either. But this doesn’t mean that you can get rid of any geographical reference.

In 2007 I made a rectilinear Moscow Metro map as an experiment:

While the principles of the above diagram are easy to figure out, there still is a problem: even if you live in Moscow, you will have a hard time finding your station.

Since any map is perceived in reference to the image of reality formed by the geographical maps, you have to respect that. If the reader knows roughly where a station is in the city, they should be able to find it on the diagram, too.

Dec 22   information display   maps   transportation   wayfinding

Map and reality: layers

In Map and reality: distortion I talked about how distortion is inevitable on a map and the question is what to distort given a particular task.

Now let’s talk about layers. What properties of land should a map display?

Physical and geographical world atlas (1964)
Physical and geographical world atlas (1964)

A physical map shows terrain: oceans, trenches, plains and mountains. On a political map, the land is divided into countries and states. A mineral resources map is covered with the symbols of mineral deposits and oilfields.

One can’t say that a physical map is “truer” than, say, a railroad atlas. The following map shows the history of Amsterdam’s development, and it’s also true. Red houses are the oldest, the blue ones are the newest:

Buildings age in the Netherlands

A good cartographer will find ways to display lots of data on a map:

A map of Chelyabinsk region, Russia (1956)
A map of Chelyabinsk region, Russia (1956)

This map displays terrain, the region boundaries, motorways and railroads, settlements, ponds, mountain ridges, height markings, parallels and meridians.

By carefully choosing colour shades, widths and styles of lines, typefaces of text, the cartographer achieves clear separation of visual layers. Background colours that marks the heights are unsaturated to let one see the labels clearly. A particular hatching is used along the region boundaries to make them well distinguishable. The letters У Р А on the left separated by many other designations, are perceived as one label ЮЖНЫЙ УРАЛ (Southern Ural) on the full map thanks to a special typeface.

The more features are shown on a map, the more interesting it is to explore it.

However, there are circumstances that do not suggest an unhurried examination by a curious reader. Sometimes a map should just answer a narrow set of practical questions.

A pedestrian map shows the main landmarks, sidewalks, bike lanes, subway stations, toilets and Wi-Fi zones:

WalkNYC wayfinding system (2013)

A nautical chart displays water depths, navigational hazards, important routes, harbours and the details of the coastline:

A nautical chart

The depths are marked with numbers — while the shades of blue as used on physical maps are more illustrative, a sailor wants the actual values. The dry land gets very little attention.

The choice of the layers and the way to separate them, as well as the choice of appropriate distortion, depends on the map’s goal and supposed use.

Continued in Map and reality: diagrams.

Dec 12   information display   maps   transportation   wayfinding