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Specialization restrictions
The specialization restrictions are based on the two following
principles:
• One camera can control only one direction efficiently.
Therefore, if two parallels directions have to be controlled,
a second camera should be installed. In practise, a camera
cannot cover a lane over 3.5 meters wide. For wider lanes,
a second camera should be deployed or the path should be
narrowed by using vegetation, ground markings, etc.
• One plate camera cannot efficiently provide both a clear
view of the plates to be used by the software and
contextual images of the vehicle's environment. Therefore,
one or more dedicated context cameras must be used to
provide a clear, colour, wide-angled view of the vehicle and
its environment.
Plate visibility restrictions
In order for the plate to be correctly analysed by the software,
it must be well visible to the cameras. Therefore, the camera
location must be selected so as to minimize the risk that the
plate may be permanently or temporarily hidden at the
moment when it should be visible to the camera.
The most frequent problem comes from the plate being
hidden by another vehicle too close from the vehicle to be
controlled. To avoid this risk, Sony recommends filming the
vehicle from the front and placing the camera at a height
(while respecting the limit of angle constraint, indicated at a
later stage in this document) so as to have a view from
above of the plates.
When there is an access control barrier, filming should be
carried out within a distance of four meters in front of the
barrier.
Filming from in front
Filming within 4 meters before the barrier
It is preferable that the barrier, when lowered, is not in the
image. If this can't be avoided:
• The camera should be far enough away from the barrier so
that the barrier does not occupy more than one sixth of the
height of the image.
• The barrier when lowered should not be directly between
the plate and the camera once the vehicle has stopped.
This usually means in practise that the lowered barrier
should not be in the lower half of the image.
• The barrier should ideally be located in the top half of the
image.
The barrier should not have any inscription which could
provide a signal similar to that of a number plate.
Bad position for the camera:
Good position for the camera:
Camera too close from the barrier:
Barrier to low in the image:
Camera
Camera
Camera
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