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Number crunching
You couldn’t possibly describe ANPR as a new technology. First developed in 1976, the technology has been deployed at the roadside since the early eighties and is today widely used in both public and private sectors. So why is there such a buzz around ANPR today?
The answer is simple – a raft of new applications have emerged for the technology while at the same time exciting innovation is taking place in product development. Together, these two trends are pushing ANPR to the top of the agenda.
One of the most exciting recent developments is the launch by Watchman this month (September) of a new state-of-the-art high definition (HD) ANPR system which allows up to four lanes of traffic to be simultaneously monitored using just one camera. The Watchman HD system uses a true two megapixel camera and, backed by some very clever software, can deliver clear number plate images for multiple lanes of traffic moving at high speed and in all light conditions.
Using a wide angle the high definition camera delivers, compared to the analogue camera, a huge image. According to Jim Barnard, Watchman MD, if an analogue camera were to cover the same ground the number plate image would be so small it would be unreadable. “What we are able to do with the high resolution image is expand it so that we have a very clear picture of the number plate.”
The secret, he says, is intelligent vehicle tracking throughout the field of view. What this means is that the camera picks up the number plate as soon as it appears in the picture and then tracks it until it leaves the picture. “Effectively what we are doing is putting the brakes on the vehicle. If you have a single point where you read the number plate, you may have just one hundredth of a second to read it. What we are doing is grabbing the plate as it comes into view, then following it down for the full second that it is in the picture. So, if you have 10 or 12 frames per second, you will have 10 or 12 images, instead of just one snapshot.”
What this adds up to is high level of read accuracy, typically in excess of 98 per cent. And this happens regardless of how many vehicles are in the picture at any one time. So, for a three lane motorway for example, which with conventional systems would have required one camera per lane, and additional infill cameras to ensure that vehicles changing lanes are picked up, there is now an option to use just one camera.
As you would expect, the number plate image is accompanied by an overview image. A new development in the pipeline which is scheduled to become available during the fourth quarter of this year is a completely new approach to the still overview image. Jim Barnard says that they will be replacing it with video footage.
The Watchman HD system will be offered in two versions. The LITE version is being aimed at the commercial world and the Watchman HD PRO is aimed at high volume users such as the police and local authorities and is designed to transmit data to a central server where it can be processed. Jim Barnard says that the PRO version can be tailored to suit the application. “We have done a lot of work to ensure that our HD system is backed by very intelligent processing. All the software both for the back office interface and for the triggering device have all been developed in house using our own source code.”
Jim Barnard and his team are, justifiably, very proud of the new system. As Jim Barnard puts it, instead of a fuzzy analogue image, users will have a clear HD picture. “You will be able to zoom in and even see the driver’s face.” And he sees some big advantages in having a complete field of view available when incidents occur. “The data records will provide an accurate picture of overall lane activity immediately before and after an incident. That means that vehicles contributing to the outcome but not necessarily involved in the actual incident can identified and, if necessary, traced.”
While the camera, and the quality of the images it produces are very important, there is more to an ANPR system than simply producing an image. How and where the licence plate data is processed and stored are also major issues, particularly as systems become more common and more extended. CA Traffic addressed this issue earlier this year when they launched a new ANPR system, Evolution, developed around the concept of a web server based in-station system.
Bernard Greene is CA Traffic’s MD and he explains that rather than simply offering stand-alone software with cameras, CA Traffic are offering a service. “When you buy an ANPR camera system and put it onto your server, there are all sorts of operational issues which have to be addressed such as IT involvement, firewalls, technical support, training and maintenance to mention a few. What we are doing is providing our customers with simple, easy access to data without all the headaches that go with installing and maintaining a new software system.” This is a hosted service and the server doesn’t care which client it is processing data for, says Bernard. “The client accesses the system via his desk PC web browser. The client can see the data, download the data and the service can continuously deliver data live into the client’s own database management system.”
Access to the system is controlled by a combination of user name, password and IP authentication. Data within a client’s area is segregated into raw data (number plate, time, date and location) and processed data (link journey time, turning movements etc). Access to either data is only permitted to authorised users. It is therefore possible for one agency to access journey time and another access the plate data and it is for the client to specify who can access which data tables.
At the heart of the CA Traffic system is a brand new fully integrated camera capable of providing two-lane coverage. The technical development work was led by Dr Peter Billington, the architect of the Trafficmaster ANPR network. More recently, Peter has been the Technical Authority for the national ANPR and journey time measurement work of the National Traffic Control Centre.
CA Traffic say the system can work as an “average speed over distance” check and will provide a new approach to checking and monitoring localised speeding complaints. The cameras send the data direct to the server via GPRS or 3G and once in Evolution, the real-time data can be accessed.
The service can be used with fixed cameras where there is mains electricity but with mobile communications it can also be used for temporary surveys, or as a portable system mounted on tripod. Bernard says this means that a sophisticated ANPR system can be used dynamically to provide the full functionality of a static system but on a temporary basis. “This flexibility and ease of use has not been possible before and we are confident that what we are offering a unique and much needed product.”
