Fugitives are excellent radiant heat sources. Night or day, thermal imagers can find people hiding in foliage, in dark areas, and in other hiding places, because they see the heat radiated from the subjects. By searching for a fugitive with a thermal imager, officers can apprehend a subject without giving away their own location and with out blind sweeps involving many officers. A bird's-eye view is a tremendous advantage for a police force, but at night, helicopter surveillance is far less effective. A hand-held thermal imager may be used onboard the aircraft to regain the advantage of flight.