Jon Stewart and Stephen Colbert held their Rally to Restore Sanity and/or Fear over the weekend. The media largely ignored the event; as they were one of the underlying reasons for the rally. Despite their lack of attendance, they were still somehow able to use twitter to estimate the crowd size:
While this is obviously a joke by Colbert, I thought it would be interesting to actually try and determine the crowd size using satellite imagery as I did with the inauguration. I downloaded the high-resolution satellite image, courtesy of GeoEye, and traced the obvious population areas in Adobe Acrobat. Using the resulting polygons, the area can be calculated:
(Click the image for a larger version)
The effective scale is acquired by measuring the diameter of the Captial Rutunda (which we know to be 96 feet) on the image, and converting to real world measurements. In this case, every 1.15 inches represents 96 feet.
To convert from square feet to people, I used an old standard for crowd density during fire induced evacuations. This may not be the best, or most accurate metric, but it provides at least a baseline estimate. If you have a better method, feel free to use the area number I came up with and leave a comment with your own methodology.
In the model, all people are modeled in circles individually to consider human spatial requirement. The diameter of a circle is determined as 0.4 meter with consideration of the size of body. Using the distance between evacuees and spatial requirements, interactions between people are assessed. It is an important factor in predicting congestion or contra-flows of a crowd.
Source: Building and Fire Research Laboratory via NIST.gov
In using the fire escape estimate, a circle with diameter .4 m contains 0.125 sq. meters. Converting this to ye' good ole English System yields one person per 1.35 square feet. Applying this to our area estimate yields a total attendance of 211,709 citizens for sanity.
Updated on November 10, 2010 at 6:55:00 PM CT