system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How are crowds counted (at non-ticketed events, like protests and riots)? How do they figure 20 or 50 thousand people showed up for a non-organized event?
gpt
They divide the total area occupied by people into small parts. They count the number of people in a few parts, average that, and multiply by the number of parts they made. The more small parts you add to your average, the more accurate your number will be.