What I Have Learned About License Plate Recognition
August 4, 2022
“License Plate Recognition? What is this about?” This was my first reaction when I received the job offer alert on LinkedIn, four years ago.
Despite my literature degree, I had always worked in technology positions, and when I read that the selected person would spend a whole month in Paris, I really didn’t care. I didn’t even ask myself what kind of technology Survision provides.
Regular cameras were not made to read license plates, so they depend too much on external factors
to work properly.
So, I went and I met the company CEO, Jacques Jouannais.
After a few standard questions, Jacques started talking about the company’s deep commitment to its mission; a passion rarely seen in the corporate world.
He talked about day-by-day activities such as tolling, parking, car access, gates, etc., which can be more than just simple tasks. Adding LPR to the mix can introduce great benefits for both clients and operators. What was behind a toll? What happens when you take your ticket in a parking lot? He was passionate about the details and the possibilities.
To make a long story short, they accepted my application, and I decided to go with my gut (again). I took the job and flew to Paris to meet the entire team.
The first guy I met was Joel Journaux, one of the founders. Now in his 70s and already retired, he kept coming to work every day on his bicycle, reading each license plate on his way.
Some days later, I asked him how he started this business and his answer was:
“I got fired and had nothing to do, so I started playing with the OCR engine I had developed for the company I was working for. I thought it was funny to read license plates so I took a camera and started recording vehicles from a bridge in Paris and spent the night improving my OCR to read those tags.”
Along with other “smart fired guys” who saw a business opportunity in his weird “hobby,” he founded the license plate recognition company, a candy really hard to sell at the time. Nobody in France was interested in reading license plates, until something happened: London’s government issued news about installing LPR cameras all over the city.
It was 1993, ANPR was deployed for the first time as part of a “Ring of Steel” camera network around London to end a string of terrorist bombings in the financial district. In 1997, all data collected by ANPR police cameras in all UK was already centralized nationwide.
Paris authorities saw a big opportunity to improve the city’s security by adding ANPR to their surveillance systems. They went in search of the French ANPR providers and the funny engine that read license plates, and the rest is history.
This is how Survision was born and this story still represents what Survision is nowadays: a truly R&D-focused company; too much, I would say! But nonetheless, this devoted passion is the inspiration I need (as head of the marketing department) to tell this story. This is how my LPR journey started and I learned so much from that day.
The most important and/or curious things I learned about LPR:
License Plate Recognition is really a four-stage process:
1- Localization: Finding the License Plate number within the whole image, disregarding unnecessary data and focusing on the characters.
2- Segmentation: Separating the precise zone containing every character to identify them separately.
3- Identification: Accurately recognizing characters from every zone.
4- Regionalization: Identifying ambiguities due to differences in plates design around different regions (countries or states).
An interesting thing most people don’t know is that the most difficult step is not the OCR itself, but the localization of the license plate in the image.
There is no such thing as
Off the shelf LPR”
Correctly reading license plates in real-time is a complex technique that involves making the site conditions “work for you” in order to get the best results possible; every site is different, so it must be every installation. Pre-installation support becomes fundamental in order to get a successful LPR going on...and satisfy the customer. I am 100 percent positive on this:
If you try to ship LPR cameras as an off-the-shelf product without the correct support and training for the installer, you will have an unsatisfied final client.
The right lighting is key
We discovered that one of the most influential variables is lighting. Light affects the camera performance a great deal; that is why we decided to make cameras with their own light source built-in. And they are totally controlled by firmware which adjusts lighting and other camera parameters to get different instant versions of the same picture so they can be combined to get the clearest image possible of the license plate.
If done right, LPR becomes a magical must-have.
When everything is running smoothly and the barrier “just opens,” there is no better result. At first, customers will find it magical and amazing, but the next day, they will count on it as a basic need and they will grumble if they don’t have it. As Nigel Bullers (EasyPark CEO) said: “Clients count service in milliseconds, they need those back...” and they will fight for them!
Well, to have that kind of WOW power at your facility, you have to make everything LPR-related “run smoothly” ...and for that, you have to make sure you have specialized people/equipment doing the job.
I could keep going with 100 other things that amaze me about LPR, such as the time we installed a tiny LPR camera on a Segway and improved parking enforcement effectiveness by 300 percent, but I guess further details would be for enthusiasts only (despite how passionate I can get talking about this subject, my husband says that talking about LPR is really boring).
If I get the opportunity, next time I will write an article about tips for a vacation in Italy (my home country) and it might be more fun for everybody.
If you have any questions about LPR or our technology, you can contact me.
Laura Caillot is General Manager for Survision. She can be reached at firstname.lastname@example.org