Data visualisations should represent their underlying data as accurate as possible, and timelines are no exception. However in many cases, temporal data is not accurate in the first place, as it can not easily be measured or counted. In order to represent such uncertain data accurately, we have to allow for ambiguousness in the visual representation of it.
Friedrich Strass’s Strom der Zeiten (1849, left) draws the world’s history as a fluid stream of empires in and out of each other, while Edward Lee’s History’s Largest Empires (2011, right) represents them as solid, discrete entities.
A visualisation should make understandable through an image, what is difficult to grasp in words, and enable new discoveries through visual analysis. Data visualisation in particular enables abstract numbers to be compared visually, or patterns to emerge from what might be just a list of measurements. It is always a translation, a representation of information in a graphical format, which by itself does not contain any new information in the strict sense 1 that was not contained in the raw data already. In the first instance, it makes existing information accessible for visual exploration.
Joseph Priestly stresses this aspect of his work in his Description of a Chart of Biography. The text accompanies what can be considered one of the first graphical timelines (after the pioneering work by Jacques Barbeau-Dubourg): A chart depicting the lives of about two thousand individuals, represented by lines on a linear scale of years ranging from 1200 to 1800.
It is of course an understatement when Priestley declares himself simply “to be an assistant to the great Historians, Chronologers, and Biographers” (p.4), whose work forms the foundation of his timeline. What he means, is that he did not himself produce any new knowledge, but assembled the research of others in one coherent visualisation — laborious and painstakingly of course. In reward for his undertaking, he was now able to see and also show to others, the relation and succession of historic figures, their contemporaries with whom they might have conversed, and the periods when cultural life flourished or, symbolised by emptiness, stalled. The representation of chronological information in graphical form opened it up for visual analysis and exploration, which enables new hypotheses to be developed from which ultimately new knowledge can be gained.
I mention this historic example of a graphical timeline, because it exhibits awareness for key requirements a timeline needs to fulfil, which are still relevant today. Being one of the first to ever create a timeline, Priestley gave careful consideration to all of his design decisions, which he documented in his Description.
Article Image Left: William Bell’s translation of Friedrich Strass’s 1804 Strom der Zeiten (1849), from Rosenberg and Grafton A History of the Timeline
Right: Edward Lee History’s Largest Empires (2011)
What has caught my attention when reading Priestley’s Description Of A Chart Of Biography, is how well one can relate to his process and the decisions he took when working on the chart, although he was designing for an entirely different audience and medium than we do today. It seems that the process for designing information visualisations has not changed significantly in more than 200 years.
I have extracted from his descriptions four general rules, that Priestley seemed to adhere to (consciously or not) and that I and probably many others still apply today:
Before one can begin to put data into visuals, it is important to define some guidelines on how this transformation will occur. For it is always a transformation and only when it is performed in the same way for every instance of data, it is possible to contextualise and compare.
There will be cases where a transformation can not be performed in the way intended. At first, one should check whether this might be due to a mistake in the guidelines and, if yes, adapt the guidelines for all elements. However, often this can lead to things feel right in one case, and feel awkward in all the others, at which point it is important to trust one’s instinct as a designer and break one’s own rules.
Tufte’s Data-Ink Ratio is an encouragement to remove clutter from data visualisation, however one should not refrain from displaying redundant information when it helps the usability and understandability of a graphic.
A visualisation should not be designed to simply be looked at, but to be used. During the design process one should keep in mind how a user might potentially interact and interfere with the graphic, be it a printed, digital or physical implementation.
After the jump, I will show by example how those rules have been applied by Priestley. Continue reading →
Down in the Churchill War Rooms, part of the Imperial War Museum in London, a fifteen metre long interactive timeline invites the visitor to explore the life of Winston Churchill.
An array of ceiling mounted projectors casts the pastel coloured visuals on a banquet-like table. The timeline is organised in tabs, which are marked with a year number and contain a list of the most important events. More eventful years, such as the period of World War II, are distributed across several tabs and marked with a range of months in addition to the year.
When one enters the room, the earliest years of Churchill’s life are arranged on the right side of the table, from the back of the room towards the front, while the later years are organised on the left side, from the front to the back. No connection seems to be intended between the years that are opposite to each other on the table. The colours of the boxes as well as the half circles that appear on their top edges on the other hand seem to follow some coding scheme.
To unfold the individual tabs, the user moves a yellow pointer to the desired year (portion) by sliding on a plastic touchpad below the projection. After a short delay, the tab opens and reveals another set of tabs corresponding to the selected months or days of the chosen time period. Again the pointer can be used to choose one of the sub tabs, which reveals — after a short delay — an artefact or an excerpt of Churchill’s biography.
Several touch pads are mounted on the table, each giving access to a portion of the timeline. It is not possible to interact with the entire timeline at once, nor is it possible to have several tabs open. Despite the sleek appearence and the smoothly animated transitions, exploring the timeline is a cumbersome undertaking. Moving the pointer from one year to another often requires stroking the strip several time, and there is no other option to confirm the selection despite waiting for a few seconds and hoping for something to happen.
When first trying out the Churchill War Room timeline, one tends to expect it to react directly on touch, when in fact it is controlled by the touch strip below it.
In a sense, these shortcomings do not really matter, as most visitors (from observation) do not seem to understand how to interact with the timeline. One reason is, that the control strips are barely visible below the bright visualisation.
The main problem however is not a fault of the design installation, but of the anticipations of the visitors. Primed by the technological developments of the past years, almost everyone (including the author) expects the timeline to react on touch. These expectations are assured, even after some visitors discovered the touch strip and managed to move the yellow arrow. After moving the pointer, nothing happens at first. Therefore, the user decides to touch the projection, at which point the tab opens — not triggered by the touch, but by the implemented delay. Yet for the user, it was the touch that caused it, which leads him to touch one of the sub tabs. Again, the tab opens. Although not necessarily the one that has been touched, because it was actually triggered by the delay and the current position of the yellow arrow.
All of the visitors around at the time have been observed to be interacting in the way described. Some of them did show apparent confusion, or seemed to be aware of the fact that they were using the timeline incorrectly. To be fair, if the installation would be developed again, the designers would most probably implement the sort of interactions expected by the users today. Still, there’s no guarantee that tomorrow’s users won’t expect a completely different kind of interactions, maybe similar to the gestural interfaces developed by John Underkoffler and popularised by Spielberg’s Minority Report.