Requirements for video camera characteristics:

  1. It is recommended to use the resolution of no more than 800x600;
  2. Recommended frame rate per second is 25;
  3. High resolution black and white cameras are recommended because they provide better quality of image at low light conditions;
  4. 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;
  5. It is recommended to use a camera and a lens with auto iris support to minimize the number of flares and maintain optimal frame contrast.

Image requirements:

  1. The geometric distortion by optics ("barrels" and "pillows") should be reduced;
  2. The image of the carriage plate numbers should be clear, contrast and readable;
  3. It is recommended to disable all the camera functions aimed for processing dark areas of bright images, brightness, color tone, contrast, etc, because these functions usually degrade image quality due to the heavy traffic and sudden changes in light which often occur in the control zone when recognizing railway container and carriage numbers.

Requirements for video camera installation:

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Passenger railway carriages

Cargo railway carriagesUIC railway carriages

Railway containers

Character height in the frame

At least 10 pixels; >= 16 pixels are recommended

Possible places for reading numbers

Carriage number

Carriage number, number on the chassis

Carriage number, number on the chassis

Roof and sides of container

Number of control cameras1–2; 2 are recommended

1–4; at least 2 are recommended; 4 – if there are platforms

1–4; at least 2 are recommended; 4 – if there are platforms

1–6; at least 2 are recommended

Width of camera control zone

5–10 meters

5–10 meters5–10 meters4–8 meters

Camera horizontal angle

<= 20°
Camera vertical angle<= 30°
Camera angle of view<= 5°

The camera height relative to the top of the railroad tracks

3–3.5 meters

3–3.5 meters for reading the side numbers, 1.5 meters for reading the chassis number

1.7–2.3 meters

2.5–3.4 meters

Distance between the camera and the carriage

1,5–10 meters (depends on the focal length of the camera lens), the optimal distance is 4-6 meters

1,5–10 meters (depends on the focal length of the camera lens), the optimal distance is 5-7 meters1,5–10 meters (depends on the focal length of the camera lens)1,5–10 meters (depends on the focal length of the camera lens)

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.

Minimum required lighting of a number

Depends on the camcorder used. Typical value is 50 lux. To illuminate the control zone at night, it is recommended to use LED lamps with a direction zone of maximum light intensity of about 90 degrees.

You can use a typical halogen spotlight with a capacity of 1–1,5 kW if the spotlight is mounted in distance 5-7 meters from the railway. Locate the 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 side of railway;
  2. image flashing by light reflection from the carriage.
Schematic representation of the spotlights  and video cameras location for the correct license plate recognition

Example of successfully recognized numbers