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To ensure the correct recognition of the

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railway carriage license plates

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• Minimum video resolution 640*480, recommended resolution 720p or 1080p

• Minimum frame rate 15 fps, recommended frame rate 25-30 fps
• Autofocus, zoom is desired (for making small adjustments after setting up the recognizer)
• Auto white balance/auto gain
• IR for night mode with good contrast of license plate images
• HDR/WDR

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• The video image should be clear, contrasting, without distortion, not blurry
• License plate size should be 15-70% of the total image size
• License plate should have no more than two rows of characters

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• The video camera should be located at 0.6-2.4 meters above the ground
• The angle between the bottom line of the license plate and the horizon line should be between 0 and 20 degrees

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• Slow to moderate (8-40 km/h)

, follow the requirements listed below.

Requirements for video camera characteristics:

1. It is recommended to use the resolution of no more than 800x600, because using a resolution of more than 800x600 does not lead to the recognition quality improvement;
2. High resolution black and white cameras are recommended because they provide better quality of image at low light conditions;
3. Recommended frame rate per second is 24;
4. The carriage motion speed must meet the camera operation speed. For a better recognition, it is necessary and it is enough to have 1-2 frames of a carriage number.
5. it should be possible to set a fixed exposure value (shutter) on video camera of 1/2000 s or less;
6. the video cameras should have high sensitivity (0,01 lx or more).

Requirements for video camera position:

1. The distance between the video camera and the carriage should be at least 1,5 meters (depends on the focal length of the camera lens), the optimal distance is 5-7 meters;

   Info
   title Note
   To simplify the setting, it is recommended to use the varifocal lenses. The focal length variation range should be selected in each case of the system installation. If you use the camera with an integrated lens with a focal length of 2.8 mm or less, then there may be strong geometric distortions on the image. As a result, the recognition quality may go down. To avoid this, it is necessary to use special removable lenses with an aspherical lens, which eliminate these distortions.

   
   

2. the cameras height for reading the side number is 3–3,5 meters, the cameras height for reading the chassis number is 1,5 meters;
3. the width of the carriage plate number in the image should be about 30-35% of the total image width, in most cases this means the width of the camera control zone is 3-5 meters;
4. the optical axis of video camera should be perpendicularly to plane of carriage plate;
5. the position of the carriage in the frame should be strictly horizontal;

6. the infrared sensor and the video camera should be located in the same vertical plane.

   Info
   title Note
   If the analog video camera is used, then to prevent the video signal fading on the transmission line, it is necessary that the distance from the video camera to the digitizing device does not exceed 30 meters.

   
   

Image requirements:

1. The minimum character height in the frame should be 16 pixels, 20–50 pixels are recommended; the line width of the character should be at least 2-3 pixels;
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2. the geometric distortion by optics ("barrels" and "pillows") should be reduced;
3. the image of the carriage plate numbers should be clear, contrast and readable.

Also it's required while video camera setup:

1. Focus camera exactly to the carriage plate;
2. disable AGC mode in video camera;
3. disable modes of adding contrast of video camera.

To provide working of system at night use searchlight flashing of carriages/cisterns. Use usual halogen spotlight with a capacity of 1–1,5 kW while mounting spotlight in distance 5-7 meters from railway. Locate spotlight as shown in the figure below. Such location allows to avoid the following:

1. Blindness of camera by spotlight directed to it from another site of railway.
2. Image flashing by light reflection from carriage.

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Reference image received from correctly mounted and setup video camera is shown in the following figure.

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