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August 29, 2010 - 12:04 am
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Zoom in on the north side: we can see the crowd is under the trees, and pretty dense at the adjacent road; it is really up to the Constitution Gardens pond:

On the south, again, the crowd goes pretty well up to the trees:

Since the last time we made an estimate, my own technology has improved. Using Google Earth, I constructed a polygon that covers the apparent area of the crowd, and another that takes in just the reflecting pool (since there are not a lot of people standing in the water).

With the aid of an excellent online tool, we find the enclosing area is about 223,000 square meters and the reflecting pool about 26,000 square meters. By applying only the least bit of advanced math, we get a total area for the crowd of about 197,000 square meters. The Park Service considers a “dense crowd” to be around 10 square feet per person, or about 0.93 square meters per person — call it 1.1 people per square meter.  If the whole area were packed that densely, we’d have about 215,000 people.

Of course, it’s clear from these pictures that the whole area isn’t that tightly packed; on the other hand, we don’t know when the photos were taken. So let’s make a range of estimates.

 Maximum: 215,000 people 90 percent 200,000 75 percent 163,000 50 percent 108,000 CBS News Estimate 87,000 40 percent 86,000

These are relatively small estimates compared to some, so let’s just note that I’m taking a very conservative approach:

• I’m only using photographs of the reflecting pool area itself.
• I’m not attempting to add in the people around the Lincoln Memorial, since I don’t have a good photo of that.
• I didn’t attempt to include people between the Washington Monument and the reflecting pool.

So these should be considered very conservative estimates, especially as we think about the lower percentages. The total could easily be, say, twice the 75 percent estimate, or about 330,000 people..

Now, as I was completing this piece, CBS News released its own estimate, based, it said, on an estimate they commissioned by AirPhotosLive.com.  That estimate: 87,000 ± 9,000. (Oddly, AirPhotosLive.com doesn’t list crowd estimation or anything that seems much similar in its services, but perhaps that’s just an oversight.)

It appears to me that 87,000 is a real lower bound estimate: that would mean that only about 40 percent of the area had a “dense” crowd. And there weren’t any people in the other areas I didn’t include.

As always, you the reader will have to draw your own conclusions.

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Charlie Martin writes on science, health, culture and technology for PJ Media. Follow his 13 week diet and exercise experiment on Facebook and at PJ Lifestyle