How are the numbers collected?
In most cases, either the police or the organizers do this. However, they do not have a uniform method for counting. Often these are estimates rather than exact numbers, says Dr. Stephan Poppe, who deals with participant counting at events and demonstrations at the University of Leipzig.
“Capturing demonstrations in their entirety is a very difficult and complex matter.” Dr. Stephan Poppe, University of Leipzig
Possibly the most accurate method is that the participants are counted by hand. This is possible as long as it is manageable.
For larger demos, like those last weekend, there are several methods of recording: One is that areas on the demo site are marked out virtually. The first step is to count how many people are standing in how many square meters. This number is then extrapolated to the total area.
According to Poppe, it is also conceivable to count using a software program that checks video material. This video footage could have come from a drone flying over the gathering of people.