CarR Guidelines

11/03/2015
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Cameras which are used for number plate recognition require good camera positioning and a proper field of view for best performance. ‘Normal’ CCTV cameras are often positioned to provide an overview of a scene. This however, is not a good setup to scan for license plates. To have the highest hitrate (scanned number plates) the camera should be zoomed in on where the number plate is to be scanned.

There are several guidelines to have the best performance:

Scan back, front or both sides of the car.
Proper camera positioning is critical for good performance.
Only scan one single drive lane.
Vertical angle less than 30 degrees. FrontAngle
Horizontal angle less than 15 degree. SideAngle
License plate should be viewed as horizontal as possible. PlateAngle
Minimum size of the number plate should be at least 1/4 of image width (based on an image of 768 pixels wide).
Max shutter speed: 1 / (V * 11) seconds (V = speed in km/h).
License plate should have sufficient contrast. PlateContrast
We recommend to use extra IR lighting and IR pass filter on lens.
A MJPEG Codec with low compression rate is also recommended.


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