An Introduction to ANPR

Automatic number plate recognition is a hot topic in CCTV installation, ANPR system is used in many places in the UK and rest of the world. In particular, in the UK, an ANPR system is used by government authorities to fight against criminals and to ensure the safety and security of the UK citizens. Automatic number plate recognition is used in commercial application such as car park management, tolling and many other areas.

The need for CCTV installers with specialised skills and knowledge in installing an ANPR system has become very demanding. If you are a CCTV installer and want to know more about ANPR systems, this article explains how an ANPR system works and how to set up an ANPR system.

What is an ANPR system?

In order to understand ANPR, you should understand the components in an automatic number plate system. There are three basic components; camera, recorder and database. Once a vehicle passes an ANPR CCTV camera, the camera will capture the image and it will be stored and checked against a database to see whether there should be any action to be taken. For example by giving an alert to the user, closing the barrier, disabling a device and etc.

We will now look into each of the components and see how they differ from a conventional CCTV system.

ANPR Camera

There are many things to consider in capturing a moving vehicle, for example your camera should have enough frames per second to capture a fast moving vehicle, light reflection from vehicle’s headlight should not obstruct the camera from capturing the image, the correct lens size should be used to capture a number plate clearly, correct illumination levels are used, correct positioning of the camera and so on.

There are many specialised CCTV cameras available for an ANPR application; these cameras are not the same price tag as normal CCTV outdoor cameras. However, they are most effective in capturing the number plate.

How does it compare number plates against a database?

Most of us puzzle that how an image captured by a CCTV camera is compared with a database. When an image is captured it will be converted in to binary or machine language using optical character recognition. In optical character recognition, ASCII will be used to covert a character to binary.

If you want to convert letter c (lower case) to binary, it will be converted to 01100011.

When a vehicle approaches, the camera takes number of pictures of the number plate and selects the best one to store, please note that there are many types of ANPR software’s in the market and they may deploy a different technique, for example one picture of the car plate and so on.

What is RETRO-REFLECTIVE?

Flexible retro-reflective material is constructed by hundreds of retro-reflective glass beads which will collect the light and bounce back to the same source. It helps to see the object clearly even in dark environments, pretty much like your HV vest. Most number plates in Europe and the rest of the world uses the same technology.

In summary you have to understand all components involved in an ANPR system to deliver an effective system to your customer, remember that an unsatisfied customer means an unpaid invoice.

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