Crowd counting

Crowd counting can also be defined as estimating the number of people present in a single picture.

According to a report by Life's Little Mysteries, technologies sometimes used to assist such estimations include "lasers, satellites, aerial photography, 3-D grid systems, recorded video footage and surveillance balloons, usually tethered several blocks around an event's location and flying 400 to 800 feet (120 to 240 meters) overhead.

These image pyramids are generally employed for crowd counting in places where people gather to perform rituals or practice their religious beliefs.

However, as employing the required algorithms for image pyramids is very expensive, it is financially unstable to depend on these methods.

Then, the models shall decide the density maps of the area by using the “pedestrian’s location, shape, and perspective distortion.”[8]  As there are many iterations of the algorithm and scanning processes taking place, the number of people is counted via the head of the person.

Crowd counting plays an important role in “public safety, assembly language, and video surveillance”[9]  amongst many things.

Another memorable incident occurred when Louis Farrakhan threatened to sue the Washington, D.C. Park Police for announcing that only 400,000 people attended the 1995 Million Man March he organized.

At events in streets or a park rather than an enclosed venue, crowd counting is more difficult and less precise.