Maps are amazing for their ability to show us something we can’t see directly, from the path of the Curiosity rover on Mars, to the tangle of underground fracking wells in North Dakota, to clusters of unvaccinated schoolchildren in California. For journalists, maps can be both a powerful data-visualization tool and a reporting tool.
“Maps are some of the most information-dense ways of communicating data,” says Len De Groot, director of data visualization at the Los Angeles Times. People understand maps intuitively because they use them in their everyday lives, De Groot says. “You can do a lot in a map because people already understand the fundamentals—unlike, say, a scatterplot.”
Maps can also reveal relationships and stories that aren’t otherwise apparent. In the mid-2000s, De Groot was part of a team at the South Florida Sun-Sentinel that mapped FEMA disbursements after several hurricanes, including Hurricane Frances, which struck in 2004. “We didn’t start with any agenda, we were just doing the standard where’s-the-money-going thing,” he says. “To our surprise there was one zip code in Miami where we saw there was a spike in payouts in areas where we knew there was very little damage.” That led to a broader investigation by the paper, which revealed widespread fraud and got the paper nominated for a Pulitzer Prize and ultimately led to policy changes at FEMA.