Line crossing detection is a video analytic that draws a virtual line in the scene and raises an event when a person or vehicle crosses it in a chosen direction. It turns a camera into a directional tripwire without installing a physical sensor.
The analytic is only as good as its calibration. A line drawn on the camera image does not correspond to a boundary on the ground unless the scene has been set up for it.
Setting it up so it works
Draw the line across the path people actually use, set the direction, tune the minimum object size, and test at night when headlights and shadows arrive.
What still gets through
Rain, snow, insects near the lens and swinging signs cause false triggers. Classifying humans and vehicles rather than any motion removes most of them.
Related:Commercial security camera systemsGlossary: Video management system