Conservatives measure up.

There has been a small kerfuffle brewing over differing estimates on the size of the crowd that watched Glenn Beck sermonize on the Washington Mall (mount) last week. He says at least 500,000 attended.

CBS hired a company with experience in crowd size evaluation, AirPhotosLive.com, and they estimate the crowd at 87,000.

According to the CBS news site articles by Alex Sundby and Brian Montopoli :

...AirPhotosLive.com gave its estimate a margin of error of 9,000, meaning between 78,000 and 96,000 people attended the rally. The photos used to make the estimate were taken at noon Saturday, which is when the company estimated was the rally's high point. Rally organizers had a permit for crowd of 300,000. Crowd estimates used to be provided by the National Park Service, but the agency stopped counting crowds in 1997 after being accused of underestimating the size of the Million Man March in 1995. 

Curt Westergard, the president of AirPhotosLive.com, agreed to discuss his methods. Westergard's company has done aerial imaging for the U.S. border patrol, the Department of Homeland Security, companies building skyscrapers and cell phone companies trying to decide where to build their towers, among others.

"People hire us to get a really detailed view of what's on the ground," he said.

 The company sometimes uses these images for crowd estimates, both generating its own estimates and partnering with Professor Stephen Doig of Arizona State University, a Pulitzer Prize winning journalist and crowd estimate expert, to come up with figures. For President Obama's inauguration last year, the company worked with Doig and GeoEye satellite data to generate a crowd estimate on behalf of CNN that was cited by the Associated Press and other news outlets.

 To calculate attendance at the Beck rally, AirPhotosLive.com used what is called a surveillance aerostat balloon to take pictures from both above the event and closer to the ground. In the video above, which was provided by the company, you can see some of the images used to come up with a figure.

The balloon, Westergard said, gave the company the capacity to move up and down, allowing it to photograph people who were standing beneath trees in addition to taking photos from high above.

"Crowd counting, particularly of political events, always is controversial," he wrote. "The organizers of the event inevitably hype their crowd estimate -- often grossly -- to demonstrate the popularity of their cause, and opponents inevitably underestimate to fit their own agenda. Because of the wild pre-inauguration predictions of how many would attend in person -- up to 5 million! -- my reality-based estimate was ignored by many left-wing commentators and embraced by those on the right."

 He added: "The frothing underscores the problem with hyped predictions of crowd size. Organizers and supporters are forced to insist loudly that the actual crowd met or exceeded their expectations, for fear that the realistic estimate will be painted as a disappointment. The time-honored way to dismiss scientific estimates that don't reflect the pre-event hype is to claim political bias on the part of those doing the estimate. I am amused to see that those who embraced my Obama inauguration estimate as soberly realistic are now attacking the Beck rally estimate, produced using exactly the same methods, as deliberately biased."

On his Fox News show, Beck used an Associated Press photo taken from the Washington Monument to support his claim that there were at least 500,000 people at the event. He said that, looking at the photo, it was obvious that a nearly mile-long area was nearly completely filled with people, evidence that the CBS News-commissioned estimate was far too low.

But Westergard said it's a mistake to try to count crowds that way, and noted, as you can see in the video above, that people bunched in front of jumbo-trons and did not tightly fill out the entire area.

"You really have to have a position overhead to count it well, and if you use a very oblique angle from the top of the Washington Monument, the sparse areas - and there were many because of people with blankets and chairs - tend to look more dense because you're looking at it from the edge," he said. "We instead are looking at it from above. And that perspective is essential. Anything less than that is sort of like guessing how many people are in a line by just looking at them through a doorway, for example."

Westergard said he has received hundreds of hate mails and angry phone calls over his estimate of the Beck rally.

The Blue Heron Blast will be the first to admit that we have absolutely no experience in the arcane science of crowd counting. However given the choice between a recognized professional in the field and a bag of wind on the order of Glenn Beck, we tend to believe the professional. Who is obviously a participant in a vast left wing conspiracy.

The wide gulf between the two figures is what we find the most fascinating. It would be petty for me to even suggest that it resembles the chasm between tea bagger policies and reality as we know it. So I won't.