A thermal imaging camera detects infrared radiation emitted as heat and renders it as an image. It works in total darkness and through light fog or smoke, and it is used to detect people and vehicles across open ground, but it produces no facial or plate detail.
Thermal cameras answer a different question from visible cameras: not who is there, but whether anything is there at all.
What the sensor reports
Thermal resolution is measured in pixels, such as 160 by 120 or 640 by 512, far fewer than a visible sensor. Detection, recognition and identification happen at different distances, and a low-resolution sensor detects presence without identifying it.
Where they earn the cost
Perimeters, open yards, roof lines and unlit storage areas suit thermal detection, often paired with a visible camera pointed at the same spot. Indoors, heating, glazing and reflected sunlight can confuse the picture.
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