Sept. 25, 2011
Technology reporter John Markoff fell and injured himself while biking in the hills south of San Francisco, and later had no memory of the fall.
But his bike did have a GPS device, which allowed me to diagram his crash for The New York Times.
I started by mapping the latitude and longitude data from his four-hour ride in Google Earth.
As soon as I saw the shape of his outgoing and return route, I was reminded of the famous map and diagram of Napoleon’s March by Charles Joseph Minard, which is frequently praised as “probably the best statistical graphic ever drawn.”
The details of the crash site were barely visible at this scale, but rotating and cropping the map gave a good sense of the start and end of his ride.
The first version of the graphic was roughly drawn with placeholder roads and charts, to test whether a Minard-inspired layout would actually work.
Times graphics are usually set in custom versions of Franklin, but I chose the serif typefaces Cheltenham and Imperial, which appear throughout the newspaper.
NYT Franklin Headline and Franklin Light.
NYT Cheltenham Book and Imperial.
Later versions of the graphic were all refinements of the initial sketch.
I wanted accurate roads with a hand-drawn feel, so I redrew the roads by tracing over a satellite image.
Minard uses an elegant scale based on Lieues communes de France, or common French leagues, each 2.76 miles or roughly an hour’s walk:
... which I adapted to miles:
After drawing the map, I charted the rider’s altitude, heart rate and speed data to match ten selected points along the return ride.
Minard uses solid black lines to connect the army’s return route with the temperature chart, and adds tight cross-hatching to make the temperature data stand out from the other solid lines:
But solid black lines seemed too dark and heavy for my narrower graphic, so I drew dotted vertical lines to connect the charts with the map, and added faint hatching under each chart.
Some in-house readers did not immediately realize that the three line charts were meant to be read from right to left, so I added a small arrow to make the direction clear.
The final graphic shows the rider maintaining a fairly steady heart rate and speed uphill to Skyline Boulevard, which follows the ridge line. He comes to a full stop at the crossing, and his heart rate begins to settle as he begins his descent and picks up speed before the crash.
Edward Tufte notes that Napoleon’s March plots six variables: “the size of his army, it’s location on a two-dimensional surface, direction of the army’s movement, and temperature on various dates during the retreat from Moscow.”
Out of respect for Minard, I avoided charting more than six variables. My graphic does not use line width to represent data, or note specific times along the return route, but it adds two line charts to match Minard’s six variables.
Markoff’s Ride is certainly no Napoleon’s March, but it may well be the best statistical graphic ever drawn about John Markoff’s bicycle.