An onboard monitoring device includes at least one image receiving device for
receiving images coming from a rear of the vehicle, an image processing unit operateably
connected to the at least one image receiving device to receive signals from the
at least one image receiving device for analyzing the images so as to determine
dimension change rate of the images based on velocities of the images, and a microprocessor
operateably connected to the image processing unit so as to receive image signals
from the image processing unit to determine locking status of the at least one
vehicle door.