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Automatic Number Plate Recognition Systems

Some innovative IT technologies for Automatic Number Plate Recognition, are already on the market.

These types of technologies scan the registration plates issued in different countries, and checked within four seconds whether the vehicle crossing the check pint, was stolen, driving with with fake numbers and if there are any other problems as changing the car paint, and etc.

The standard system accuracy is above 90% at the speed of the vehicles up to 180 km/h.
Currently, some European borders are equipped and secured with similar technology systems.

The technology convert the scanned plate number in a text file and check these data with any local, central or international database for confirmation. The process is quick and if no reported problem, the barrier is lifted.

Upon detection of non-compliance, a signal is sent to the border post in wireless connected device with appropriate warnings and instructions. This automated process helps border patrols to better perform their duties.

How the system works
Generally these system are base on the core primary algorithms:

  • plate localization – responsible for finding and isolating the plate on the picture
  • plate orientation and size – compensates for the skew of the plate and adjusts the dimensions to the required size
  • normalization – adjusts the brightness and contrast of the image
  • segmentation of the characters– finds the individual characters on the plates
  • optical character recognition (OCR)
  • syntactical or geometrical analysis – check characters and positions against country-specific rules

The complexity of these algorithms of the program determines the accuracy of the system. During the normalization process, some systems use edge detection techniques to increase the picture difference between the letters and the plate backing.

Off course the drivers have already invented and used a variety of techniques in an attempt to evade ANPR systems.

One of the tricks the used is to increase the reflective properties of the plate and makes it more likely that the system will be unable to locate the plate or produce a high enough level of contrast to be able to read it. Usually drivers use a plate cover or a spray do achieve it.

Other way is to smear the license plate with dirt or utilize covers to mask the plate.

But you should know that these systems are intelligent, so if an ANPR system cannot read the plate, it can flag the image for attention, with the human operators looking to see if they are wrong.


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