Please find below some basic rules of the thumb for achieving optimal recognition results.
- Rotation: The camera should be mounted in such a way that in the resulting image of a single line license plate a horizontal line can be drawn which crosses both the left edge and the right edge of the license plate.
- Vertical angle: The maximum vertical view angle of the camera is 30 degrees.
- Horizontal angle: The maximum horizontal view angle of an camera is 25 degrees. In most systems the horizontal angle is somewhere between 15 and 20 degrees.
- Plate position: Ideally, mount the camera in such way that an image of the license plate is captured where the license plate is in the center of in the recorded image.
- Occlusion: Avoid possible blocking objects in the view path of the camera such as (moveable) bars.
- Contrast: For contrast we use the difference in 8bit gray levels between the characters at the license plate and the license plate background. This difference should be at least 15.
- Resolution: For resolution we use the term pixels per stroke to define a minimum requirement for reliable ALPR. The image on the right shows what is meant with stroke. Because the stroke width is country and platestyle dependent we do not use pixels/cm. In general the resolution for best ALPR performance should be at least 2.7 pixels/stroke.
In addition, blurring introduced through high compression or motion should be prevented at all times. Any image quality requirements not met may impact the performance of the ALPR engine.
|Q1 Which product are you using?||
|Q2 How are you using Intrada ALPR?
The end-goal is to use the API for integration with your own applicaton. But we provide a Visualizer that allows you to reproduce recognition outside of your own context.
||Q3 Does the Visualizer startup correctly?
After starting the Visualizer application, do you see a screen with in the bottom-right a blue round “i” button that can be clicked?
||Q4 What is the error message?
You should notice a “failure” popup with an error message in the top row.