Strange Times: Visualising the Oddities of Time Data
By: Olivia Vane
Tags: Museums, Design, Data Visualization, History

Time is a common dimension for visualising data and people have created temporal visualisations for a very long time. The ‘earliest known attempt to show changing values graphically’ is a planetary movements chart, shown below, with time running horizontally dating from the 10th or 11th century. The timeline — mapping a sequence of events by time — is a classic visualisation form. (For a history of the timeline, have a look at the book Cartographies of Time by Daniel Rosenberg and Anthony Grafton, which has a wonderfully rich selection of illustrations.)

But visualising data in timelines can come up against the strange ways humans understand and experience time. We may agree that time is passing at a uniform rate, but there are complications. There are time zones and daylight savings. The human experience of time passing does not always match up to the rate of the clock (“time flies when you’re having fun”). Different cultures conceive of the shape and orientation of time differently. Which direction feels “natural” to draw the arrow of time can be influenced by the writing direction we use (this timeline in Arabic has time going right to left). Looking back on the past, more recent events appear in greater focus than those farther back.

In this post, I discuss how the ways we think about time shape the data we create (even if it’s not immediately obvious), taking the example of historical time. Illustrated by my own work visualising data from digitised museum collections, I explore how the designer can choose to either emphasise these peculiarities or to conceal them, highlighting other characteristics of the data instead. Time is fundamental to making sense of digitised museum collections (data that describes museum holdings: objects, artworks, texts, etc.) and visualisation can be a powerful way to analyse, explore, and present patterns and stories in this data, but it is a domain where the oddities of time data can really rear their heads.

Uncertainty

Take uncertainty, for example. A common issue with historical dates is that they are often not precisely known, but estimated to a stretch of time. Date information for an item may be given as a span (eg. 1940–45) or accompanied by some qualifier like “approximately” or “circa.” For artefacts from a very long time ago, this uncertainty can be very large.

The purpose of your visualisation and what you want to draw attention to will inform how best to deal with this. If visualising a large number of data points with uncertain date information, if you start slapping error bars on everything you’re in danger of that uncertainty becoming the entire communication of your visualisation. And your intention in visualising the data may not be quantitative analysis or to present an indisputable temporal order. You may, instead, be interested in revealing general patterns and connections across a large collection.

In a project visualising Cooper Hewitt Smithsonian Design Museum collection data (which I’ve written more about here and here) I experimented with using a collage layout to position data with uncertain dates. Photos serve as the data points, positioned at a random place within their timespan (time running horizontally). All the images are then spread out so that nothing is overlapping while keeping some portion of each photograph within its timespan (see the diagram below). The design does not draw attention to the fact that many of the dates are uncertain, but the overall impression also does not encourage the viewer to read the visualisation for precise date information. In a similar vein, others have explored using a normal distribution or spreading items in a grid structure to organise items within time spans like this.