Crowd Counting

Estimates of people at the Cairo protest vary from 10,000 to 2 million. Using ArcGIS to outline an polygon which might represent the heaviest crowd, the area is 104,000 square meters. Assuming a rather tight crowd, the average could be 2 people per square meter. So my estimate is 200,000 people give or take 50,000. And of course there are masses, coming and going, and in all the streets not included in the polygon. Anyway, impressive, but not a million. I don’t think it matters.