"The AN/PPS-5 is a battlefield surveillance radar. The system is designed to detect and locate individuals up to 5,468 yds (5,000 m) and groups of men or small vehicles up to 10,936 yds (10,000 m)"

[ http://www.militaryperiscope.com/mdb-smpl/weapons/sensors/grdradar/w0003502.shtml ]

по какому принципу определяют "индивидуумов" за 5км?

Spetznaz

Как двигающийся объект с определенными размерами..