A Guide to Automatic Number Plate Recognition (ANPR)

Automatic Number Plate Recognition (ANPR) can be useful in many ways such as traffic law enforcement, automatic toll collection, parking lot access control, and road traffic monitoring. It can bring ease to the life of common people as well as the traffic management system while mitigating the criminal cases.

ANPR is an advanced technology that enables computer systems to read the number plate automatically from digital pictures and store it in the database. It also eliminates the need to ask the witnesses, if anyone noted the number of the vehicle helping police to solve accident or other criminal cases quickly.

Automatic Number Plate Recognition works on the basis of optical character recognition (OCR). It transforms the pixels of the image of the number plate of the vehicle into the ASCII text. However, OCR technology is augmented to read the numbers on the plate of the moving vehicle. It is commonly used to scan paper documents and convert them into editable electronic files.

The first step is to take the image of the plate where the numbers are written and second is to scan them to convert into a legible form. Here taking the image is the most challenging task because the vehicle is moving and might be at very high speed. To ensure that the image does not get blurred because the object is in motion, a combination of short shutter time and high-power illumination is used.

IR illumination suites the best because retro-reflective plates reflect it. It works fine in both day and night. So no vehicle goes unnoticed where human eyes fail sometimes.

Automatic Number Plate Recognition can recognize the numbers at speed up to 250 Km/hr. This way it becomes an inevitable solution for traffic management. It is one of the most vital tools of Intelligence Traffic Management System.