Styles I like to refer to as quasi-maps are data visualizations that evoke geographic patterns but don’t adhere to absolute space (i.e. space marked by measurable distances). Like cartograms, the geography of this type of spatial visualization has been disassembled to the extent where the geographic entity is only recognizable when viewed as a whole.
Benjamin D. Hennig from the University of Sheffield has created hexagon mapping in which the United Kingdom’s geography was converted into hexagons representing the results of individual constituencies in the British 2010 General Election. As opposed to cartogram maps that seek to over or under-exagerate the size of an individual area based on a qualitative measurement, hexagon maps size each geographic area identically. For Hennings election map, the size of each constituency has been made equal, regardless of the actual geographic size of the area represented by any specific seat in parliament. This enables smaller urban constituency areas to be clearly viewed that otherwise wouldn’t be visible on a straightforward geographic map.
2010 British General Election Results Hexagon Map. Created by Benjamin D. Hennig, University of Sheffield.
The effect of using hexagon mapping can be highlighted when viewing a map that is geographically proportional as compared to the hexagon map as seen in these side by side maps from the BBC 2010 General Election Results site. As with Henning’s election map, the hexagon style of mapping out the results allows for detail in areas where the geographic extent is smaller to be elucidated.
Side by side comparison of a geographic map and hexagon map of the 2010 General Election results. Source: BBC.
Graphs as Space
It’s an easy step to move from geographic coordinates to a graph based visualization. In 2008, then Harvard student and founder of the Radical Cartography site, graphed out the World’s population in 2000. He looked at the sum of population at each degree both for latitude and longitude using two separate charts. Plotting the degrees of latitude along the X axis and the total sum of population per degree along the Y showed amazing spikes in the world’s population. Rankin found that 88% of the world population as measured in 2000 lived in northern hemisphere. Rankin also graphed out population by degrees of longitude and found that on average, the world’s population lives 24 degrees from the equator.
Population histograms by latitude and longitude. Source: Bill Rankin, 2008.
Popular online comic strip xkcd.com cleverly weaves in geographic space with this Movie Narrative Charts strip showing time along the horizontal axis and the vertical group of lines to show when characters are together at a given time.
Click on image for larger comic.
In 1861, Charles Joseph Minard, a french engineer created his now famous flow map that graphed out the ill-fated march of 1812 by Napoleon’s soldiers to and from Moscow during the brutal winter months. Minard’s graph, entitled “Carte figurative des pertes successives en hommes de l’Armée Française dans la campagne de Russie 1812-1813″ vividly describes the flow and attrition of the troop movements in both space and time. The chart begins at the Polish-Russian border where hundreds of thousands of troops in Napoleon’s Grande Armée began their march towards Moscow. In Minard’s chart 422,000 begin the journey at the border in June of 1812, crossing the river Neman, as depicted by the brown band. Early into the march, 22,000 soldiers are diverted in auxiliary movements. Eventually 100,000 survive the march and battles along the way, reaching Moscow by September of 1812. The black band visualizes the attrition of soldiers on the retreat, with the total survivors from the journey back totaling only 4,000 at the end. An additional 6,000 survivors from the side journeys north joined those survivors to cross back over the river Neman, making the grand total of survivors 10,000 that made it back to Poland.
Edward Tufte, known for his many books on intelligent information design, declared in his 1983 book The Visual Display of Quantitative Information, that the Minard graph “may well be the best statistical graphic ever drawn.” Tufte points out that the graph coherently plots the following variables: the size of the army, geographic location over time, the direction of the army, and the temperature change as the army retreated back towards Poland.
Click on graph for a larger image.
The graph shows not only the shrinking size of the army as it moved towards Moscow and subsequent retreat, but also the geographic path taken. The actual march component of the graph has been georectified. An example of the 1812 march route overlain onto Google Maps (complete with code) can be found on Stanford University’s ProtoVis site.
Napoleon’s March of 1812 on Google Maps.
The Minard graph has inspired many to replicate it and to experiment with revitalizing the data. Michael Friendly of the University of York has a page with examples of therevisualization attempts along with data samples, R code, and more on his DataVis site.