How do experts come up with crowd estimates at Washington events?
Crowd estimates in DC can be less than scientific. Case in point: Michele Bachmann’s count of 1.6 million people at Glenn Beck’s 2010 rally on the Mall. The real figure was closer to 87,000, says Curt Westergard of Digital Design & Imaging Service in Falls Church. His company estimates crowd sizes for CBS News by flying a camera-rigged balloon above the Mall. Here’s how it works.
| 1. The company spends two months arranging permits and waivers with five government agencies before it can get a camera-rigged balloon in the air near the Mall. | 2. The balloon can’t fly in the restricted airspace directly above the Mall, so Ryan Shuler, the company’s image analyst, scopes out vantage points on the outskirts. | 3. On the big day, Westergard and Shuler launch their balloon as high as 800 feet. The 13-foot-wide device has three wireless cameras and is tethered to a truck. |
| 4. Working on a computer, they lay a grid pattern over their images of the crowd. They count the people in several sample quadrants and multiply the tally by the number of quadrants with similar density. |
 5. Meanwhile, Steve Doig, a journalism professor at Arizona State University, does his own count using the same photos. The two estimates have always been within each other’s 10-percent margin of error. |
 6. After conferring with Doig, Westergard and Shuler send the two estimates to CBS News. They’re capable of turning around a crowd estimate in a matter of hours, but on average it takes several days. |
Westergard did some calculations to see what a million people on the mall would actually look like. He found that with one person per nine square-feet—less than an arm’s length apart—the crowd would stretch 5.7 miles, or all the way to Ballston.
Illustrations by Chris Philpot.
This article appears in the May 2012 issue of The Washingtonian.
Michael J. Gaynor has written about fake Navy SEALs, a town without cell phones, his Russian spy landlord, and many more weird and fascinating stories for the Washingtonian. He lives in DC, where his landlord is no longer a Russian spy.
