First, they mapped every death in Baghdad by its GPS coordinates onto a single map, and then divided it into six maps, one for every year from 2004 to 2009, over 32,000 deaths overall. “It became clear pretty quickly that year-by-year maps would show the sharp increase in violence in Baghdad in late 2006 and early 2007, so we thought the small ‘snapshots’ would be an effective way to present that,” wrote Quealy.

But when the big-picture maps didn’t feel like quite enough, the interactive teams at the Times and The Guardian each decided—independently of one another—to create another map, focusing on a single day of violence, though they chose different days to highlight.

The Times chose December 20, 2006 because, according to the data, it was one of the deadliest days of the conflict in Baghdad: “There were 114 separate episodes of violence that day, resulting in the deaths of about 160 Iraqi citizens and police officers.” Assistant editor of interactive news Jacob Harris said that Sabrina Tavernise, a Times national correspondent who worked on the project, had the idea to focus on a single day, “to provide a window into the horrific levels of violence without distancing the reader from the daily impact the way a yearly map does.”

Tavernise wrote in an e-mail that, even after narrowing it down, “digesting the data was fiendishly complicated.” She and Harris worked together on this part: each entry for that one day had to be hand counted and sorted by factors like grid coordinates, type of casualty, nationality of victim, and cause of death.

Especially important, of course, was comparing all of the reports to each other to make sure there were no duplicates. At first, said Harris, they had originally settled on a different day that month, which had appeared to be the most deadly. But then they found that the discovery of twenty-eight corpses had been recorded three different times, by three different military units. So where they had initially thought there were eighty-four deaths, there were actually twenty-eight.

This kind of duplication is common throughout the WikiLeaks reports, which is why Harris says they are careful to caution their readers about taking any hard numbers away from the story. While they could take the time to vet and tally a single day in December 2006, with its 114 separate violent events, they didn’t have the manpower to repeat that process for all 400,000 documents. (For an organization that’s working on doing just that, check out Iraq Body Count.) So while the Times team felt comfortable using the raw numbers to create the yearly-map snaphots, they deliberately did not post any hard numbers alongside those graphics on the site.

“We use the data to report on reality,” said Harris. “We don’t necessarily want to just report on what the data says.” In this instance, the data merely gave them an idea of the general pattern of violence in Baghdad across time, from 2004 to 2009. “It is powerful to see how the violence just swells like this,” he said. “But of course we have to be wary of where the data has potential issues.”

The Guardian data team chose October 17, 2006 for their “day in the life” of the Iraq war because it was “a typical day in one of the bloodiest years of the Iraq conflict - 136 dead Iraqis, 10 dead Americans and hundreds of violent incidents.” Guardian correspondent James Meek compiled and verified the entries from that day, and then guided readers through the logs from that day in an accompanying article. Then he and graphics designers Alastair Dant and Mariana Santos put together the Flash-animation map. Santos, a freelancer hired for the project, has experience with video documentaries as well as with Flash animation, which may have influenced the style of the presentation, said Rogers.

Lauren Kirchner is a freelance writer covering digital security for CJR. Find her on Twitter at @lkirchner