How is the distance threshold determined?

[davidmurray]

Hello,

In the code, I noticed that 250 is used as a threshold to classify people as being too close ("red"). However, this is a distance in pixels, not meters. How was it determined then?

Also, isn't that ignoring the problem of perspective? (if two people are close to the camera then their pixel distance will be large, but if they are far away from the camera than their pixel distance will be small).

Thanks, David