Standard ALPR cameras with video triggering detect a vehicle by means of motion detection techniques. Motion detection consists on analysing the differences between video frames. When a difference occurs, this approach considers that there is a vehicle and it captures an image to read the license plate. This technique has one main drawback: it has false detections caused by shadows of a vehicle travelling in the adjacent lane, or even by shadows of trees next to a road.
Imagsa's ALPR cameras implement a license plate detection technique. Basically, it consists on continuously capturing and analysing images to detect a license plate pattern. When there is a license plate pattern it means that a vehicle is in the field. This approach avoids the false detections that are common in an ALPR camera based on motion detection.