In reply to Reza Nazari.

Thank you for your interest.

If you'd like to learn more about how we developed a physical distancing and crowd density monitoring solution using computer vision, please see the following paper:
https://www.iiconsortium.org/news/joi-articles/2020_November_JoI_Physical_Distancing_and_Crowd_Density_Monitoring_Using_Computer_Vision.pdf
The paper discusses in a little more detail the use of heatmaps in this context.

If you'd like to learn more about the computation of heatmaps in a fast way, please stay tuned for the next blog post written by a talented colleague of mine.