How dense is “Very Dense”?

The CrowdSize application is an easy to use tool for estimating the size of crowds at outdoor events.  It has three standard density factors that can be applied to the area the user outlines on an aerial view of the crowd location.  They are: Heavy or “dense” (1person / 4sf = 2.68 persons / 1sm), Medium (somewhat dispersed) and Light (dispersed).  Crowds vary in density.  So outlining the perimeter of a crowd and applying one of these density factors based on what we see of the event can only be described as “estimating” the number of people.  But could CrowdSize do a better job of estimating the number of people in a “very dense” crowd that we might see standing shoulder to shoulder in front of a speaker.  And what does a “dense” vs. “very dense” crowd look like.
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The density factor for the greatest number of people in a group, the Heavy or “dense” setting, uses four square feet (0.37 sm) per person.  This density factor takes into consideration some circulation space or breathing room around each person (figure 1).  When we look at a sketch of this density factor for say nine people, each with his or her own four square feet of area, we see what looks a group of people that could be marching or sitting in rows of chairs (figure 2).  This is not an uncommon scenario for a crowd at a demonstration.
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However, what about describing a “very” dense crowd standing shoulder to shoulder in front of a speaker rather than marching.  Using a density factor of three square feet (0.27 sm) per person still does not quit describe the standing crowd (figure 3).  What if we look at people standing together with a density of 2.25 square feet (0.20 sm) per person (figure 4).  I think this perhaps best describes our crowd standing shoulder to shoulder.
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The CrowdSize application has an area calculation feature that can help with an issue like this.  The area calculation feature could be used here to give us only the area the crowd we see in front of a speaker.   By dividing the area of the crowd by 2.25 we can calculate a better estimate for a “very dense” crowd (1 person / 2.25sf = 4.78 persons / 1sm).  CrowdSize could stand to be improved to offer the user the “very dense” setting as one of its standard density options on the slider.

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