JAI Vehicle Imaging Subsystem 300, Installation Manual

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Page 7
VIS CAM 300/400 Installation Manual
Preparing for installation
FIGURE 4.
Typical Over Lane Site Layout Plan.
2.1.1 (a) Camera tilt considerations
The requirement to freeze the motion of high-speed vehicles limits how steep or shallow the tilt angle of
the camera may be. For example, it is important to prevent the horizon from appearing in the image,
and thereby allowing the sun to blind the camera. For over lane installations, a camera tilt between 20
°
to 30
°
is recommended–with 25
°
being considered the optimal angle. This angle of tilt is the best
compromise between minimizing visibility blockages caused by closely spaced vehicles and
maximizing plate visibility for plate mounts that are slightly recessed or tilted downwards.
2.1.1 (b) Asynchronous triggering considerations
When the VIS is operated in trigger mode, a vehicle detector is employed to cause the camera to capture
an image at the precise moment the vehicle is in the best position to image both the vehicle and its
license plate. The delay between the time the vehicle passes the trigger position on the road and when
the trigger signal actually reaches the VIS must be kept to a minimum to prevent high-speed vehicles
from moving out of the area viewed by the camera before the image is snapped.
2.1.1 (c) Continuous operation considerations
2.1.1 (d) Camera height versus trigger distance considerations
It is critically important, to select the correct distance between the camera and the location on the road
where the camera is triggered to capture an image. Minimizing the cost of installation is usually also an
important concern. This means, that whenever possible, it is best to use existing structures or previously