How Does Number Plate Recognition Work?

How does number plate recognition work?

1. Finding the License Plate
2. Segregating the Characters
3. Identifying the Characters
4. Checking for Ambiguities

Automatic number plate recognition (ANPR), sometimes called license plate recognition (LPR), is the technology used to grab license plate numbers from vehicles. It uses a camera to capture images of the vehicle and then it is programmed to eventually appear on the database. It has many applications including traffic management, parking management, and building security. It seems impossible, so how does number plate recognition work exactly?

Before we get to the specifics, let’s talk about what exactly an ANPR is.

What is an Automatic Number Plate Recognition System?

An automatic number plate recognition system is the sum of the parts that help read the license plates from a captured image. The cameras, the computers (if necessary), and the program are all parts of the system.

Thanks to its automation, no human intervention is needed for it to work. When the system successfully reads a plate number, it instantly gets all the data needed on that vehicle. For businesses, it can protect your premises from unknown vehicles that are potential security threats. Other information that you can get with ANPR is the owner, the authorization, the speed, or even where it’s been.

The EV200 ELID-ANPR system by ELID is a prime example of a plate number recognition system that needs no computer or software installation to function. It uses a deep neural networks algorithm for machine learning and has a built-in web server. This lets users control the system through a web interface. A good ANPR system should also be able to operate for 24 hours every day and under any weather conditions.

How the Number Plate Recognition System Works

ANPR systems use optical character recognition (OCR) to recognize the characters on a vehicle’s license plate. Advanced computer learning allows them to do this accurately and even with unclear images. To go into more detail, here is a step-by-step breakdown of how number plate recognition works. How does number plate recognition work? Keep reading to find out.

Finding the License Plate

The first thing that ANPR systems do is find the license plate. A camera takes photos of the approaching vehicle. This is often placed at angles where the license plate would be very visible — around 45 degrees either vertically or horizontally, as close as possible to the vehicle. Some cameras are placed near the ground while holding an upward angle for a better view.

When the image is taken, the program tries to find the license plate and disregards all unnecessary parts of the image.

Segregating the Characters

The firmware will then segregate each character from each other. It uses zones in the image to segregate them properly, identifying what zone in the photo each character fits in. By doing this, the program will be able to identify each character separately.

Identifying the Characters

Once segregated, the program will proceed reading each character. Each zone in the photo where a character is detected will be checked and identified. In the end, the program will have the values of every segment of the license plate.

Checking for Ambiguities

APNR systems are usually equipped with advanced machine learning networks to optimize their performance. It makes the recognition of characters better, even when the image and/or weather conditions are bad. One of the more complicated processes for APNR is checking ambiguities.

As a computer vision system, it should be able to distinguish ambiguous characters from each other. Is the character 1, l, or I? What’s the difference between a 0 and an O? What if the plate is smudged with mud or other types of dirt? With deep neural networks, the machine will successfully distinguish these characters and translate them from visual data to readable information for the database.

Translating for the Machines

Data is different if it comes from photos. Photos are made of pixels to depict a visual representation of the image. After the entire process of identifying characters from the image, the program will then translate it to be readable by machines and encode it into the database.

Depending on physical and technological factors, this entire 4-phase process happens in a span of seconds. After that, you may find it on the database with all the information you have on the vehicle.

Key Takeaway

ANPR systems are incredibly useful and have made it easy for businesses and authorities to track vehicle activity. It shouldn’t surprise you if parking buildings and large business compounds use this technology. Even police officers use this to track down those who break traffic laws. Overall, this technology has given us plenty of advantages because of its well-thought-out process.

If you’re looking for cutting-edge ANPR software for your building, or even access and security control systems in general, we can help! ELID develops world-class systems and solutions for building management and security, among many other things. Take a look at our products and don’t hesitate to contact us if you’re interested!