For recognition it is necessary to make sure that frames with number plates fulfill the following characteristics:
| Camera specifications | |
| Video image | - The symbols height for IP cameras should be not less than 20-30 px, for analog cameras - not less than 14-20 px, the stroke width should be not less than 2 px;
- Minimum allowed contrast with evenly dirty number plate should not be less than 10% ) contrast differentiation of symbols to the background is 25 on 256 point scale);
- Maximum allowed uneven dirtiness is not more than 12% (ratio of the dirty area of the number plate to its whole area);
- Geometrical proportions of the number plate picture should not differ from such proportions of the number plate itself with more than 10%.
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| Camera positioning | - The camera should be installed permanently (for detailed installation information, see the vendor documentation);
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| Vehicle speed | - Vehicles speed at recognition in the Fast mode stated in this document (up to 300 km/h) is provided using special cameras and frame rate more than 25fps. However, in the Auto-Intellect software, frame rate in the Fast mode is fixed at 25fps, therefore speed of vehicles in the Fast mode is limited to 150 km/h in the Auto-Intellect software.
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Examples of LP images that will be recognized correctly and completely:
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