Earth Satellites and Math used to Count Inauguration Crowd – Not Google Earth
Barack Obama was sworn in as the 44th U.S. President on Tuesday in Washington. Th number of people who braved the frigid D.C. weather to watch the historic event could have been anywhere between 800,000 and 3 million, depending on which count you take. Researchers have projected widely varying figures for the event’s attendance, based on satellites circling above the clouds, aerostat balloons tethered blocks away, television coverage of the crowd, and good old-fashioned mathematics calculations.
Steve Doig, a journalism professor at Arizona State University who specializes in counting inaguration mobs, said he’s estimating there were 800,000 people in attendance, based on a satellite image taken by GeoEye about 40 minutes before the swearing-in ceremony. “The space-based image is fascinating because all the low-level shots make you think the crowd is much larger. (In the satellite images), you see the very dense clots of people in front of the JumboTrons, but then the wide open spaces elsewhere,” Doig said. “I’d still suspect this crowd was larger than the Lyndon Johnson one, which wasn’t estimated with the benefit of an image from this excellent viewpoint.” Everyone from Rev. Jesse Jackson to Samuel L. Jackson was turned down entry though.
Estimates have put Johnson’s inauguration attendance at 1.2 million, but Doig said he thinks that figure is inflated. Using the images, the professor tries to figure out how many people there might be per square foot and then factors in the surface area. “It’s actually fairly simple math, getting the square footage and dividing that by some number of feet per person,” he said. “A scary mosh pit is 2.5 square feet per person. That’s about as tight as you can pack people, where they can’t move–elevator tight.” If people up and down the Mall were stuffed in that tight, there could have been 2 million, he said.
GeoEye collected a high-resolution image of Washington, D.C., at 11:19 a.m. EST from 423 miles in space, said Mark Brender, GeoEye vice president of marketing and communications.
“There were high, wispy light clouds, but one could clearly see throngs of people, especially gathered around the large JumboTron televisions spread along the National Mall,” he said. “The satellite collects imagery at 41 centimeter ground resolution, so one is able to see an object the size of home plate on a baseball diamond.”
