New D.C. crowd estimate: Up to 1.6 million

WASHINGTON - A new and reliable computation indicates that 1.2 million to 1.6 million people - and possibly more - jammed the capital to see Barack Obama sworn in as president.

Those figures would make the inauguration the largest event ever held on the National Mall or in the District of Columbia.

Analysts at IHS Jane's, a leading provider of defense information, created the estimate using two key tools: The first was a set of precise measurements, taken before Inauguration Day, of 71 sectors around the Capitol. The second was a GeoEye-1 satellite image taken of Tuesday's crowd at 11:19 a.m., about 45 minutes before Obama took the oath of office.

The image was used to determine crowd density, which varied enormously from place to place, from as many as 5 people per square meter to 0.1 person per square meter, according to Jane's. The firm calculated the number of people in each sector, then added the totals to produce a final crowd estimate of 1 million to 1.4 million.

That figure did not include about 240,000 people who had tickets to seating areas closest to the Capitol. If they are added, the total crowd size comes to 1.2 million to 1.6 million.

"I think that's a very realistic number," said Temple University instructor Ira Rosen, who studies crowds and has put on big public events through his company, Entertainment on Location. "It's relatively easy to calculate some of that, because if you look at the National Mall, a lot of it is unobstructed. There are no trees, no buildings."

The previous largest gathering in Washington is reported to have been the 1965 inauguration of Lyndon B. Johnson, which drew 1.2 million, according to newspaper articles of the time. But those accounts were almost surely in error, because Johnson was inaugurated on the east side of the Capitol, facing a sea of buildings, not the open expanse of the mall.

The next-largest crowds were 1 million for the 1976 Bicentennial Celebration and 800,000 for the first inauguration of Bill Clinton in 1993.

The Jane's analysis included three caveats that would actually push the total estimate higher:

Jane's had no way to count the people who watched from nearby buildings. The satellite image did not include the White House or nearby public squares. And the fact that people were grouped at security checkpoints at 11:19, when the satellite image was taken, strongly indicates that crowds were still arriving, according to Jane's.

The analysis could well stand as the most authoritative report on the topic, since the city police and the National Park Service, which has jurisdiction over the mall, do not provide estimates.

Traditionally, the people responsible for estimating crowd sizes have been government officials, police, journalists and event organizers. In recent years, that work has moved toward much more scientific estimates.

At the inauguration, another quantifiable figure pointed to an unprecedented number of people Tuesday. The Metro subway system set a one-day ridership record of 1.12 million trips. That broke the record of 866,681 - set Monday. The figure could have been higher but for delays and occasional stoppages.

Rosen said he wasn't surprised by the crowd size, saying, "People felt that in spite of the crowd, in spite of the cold, 'I want to be there.' "