Things to keep in mind when using ANPR for vehicle access control
On SecIndGroup.com we talked before about various technologies that can be used to identify vehicles. License Plate Recogntion (LPR) or Automatic Number Plate Recognition (ANPR) is one of the most used technologies. The technology is used in all kinds of applications. Access control is a typical application where ANPR is used frequently and successfully. ANPR cameras are used all over the world to identify vehicles and allow them access to parking facilities, corporate estates, city centers and other secured perimeters.
Popular ANPR Camera: Tattile VEGA Basic
One of the most used ANPR Cameras worldwide for vehice access control is the VEGA Basic from our First Class Vendor Tattile. This Italian manufacturer is one of the major ANPR brands worldwide. The combination of European quality, Italian design and cost-effectiveness of this camera has resulted in numerous applications and deployments of VEGA Basic. Tattile has shared some of their design considerations with us. We have converted these ideas in recommendations to consider when setting up a vehicle access control application with ANPR cameras like VEGA Basic.
Typically a vehicle access control applications is built up using three core components:
- An ANPR Camera that is reading the license plate and that is able to send the plate information to…
- An Access Control Systems or Parking Management System that is used to manage a whitelist or authorization database which specifies who is allowed access at that date and time and
- A physical barrier (like a bollard or rising arm barrier) that opens when an authorized vehicle is detected and identified.
Of course there are numerous variations to this topology possible. Tattile ANPR cameras can, for example, also store a whitelist locally and run stand-alone, without an additional access control system.
Another variation is that the perimeter entrance is monitored using ANPR cameras, but that there is no physical barrier. This is for example the case in ticketless parking applications.
Keep things simple
To keep the topology simple, Tattile advises to use cameras with embedded software that is able to detect and read the license plate. With Tattile VEGA Basic all the OCR processing (optical character recogition) is executed on the device itself. No additional licensing is needed and no additional software needs to run on the server.
The VEGA Basic connects to the access control systems using industry standard interfaces like IP, RS485 or RS232. The interface is documented and the cameras have been connected before to many access control systems and parking management systems.
To finetune the installation, installers connect to the ANPR camera using a browser on a laptop. The embedded web server will show a comprehensive user interface that can be used for finetuning the installation.
Most professional high-performance license plate cameras were purpose designed for their task of finding and reading the number plate on vehicles that approach the barrier.
Any license plate camera works best when it has clear sight on the license plate. Keep in mind that ANPR is an optical technology, which means that the camera performs best when it sees the plate well. The reading distance shoud match the best focus range of the camera lens (for VEGA Basic Short Range that is typically between 5-8 meters) and the pan- or tilt angle must be within a certain range to make sure the license plate image is not too much distorted.
Consult with the supplier of the ANPR Camera that you are planning to use to understand the physical installation parameters that will result in the best performance.
Typical parameters related to installing an ANPR camera are the reading distance (D), the installation height (H), the width of the lane (W) and the offset or distance to the road (O).
Most ANPR cameras use Infrared Light (IR) to detect and read the license plate. The advantage of this is that this light is normally not see by human beings, which makes it a non-intrusive technology.
Tattile cameras that use infrared light will have IR-illuminators on board. No additional lighting is needed and the cameras will remain operational even when it is completely dark.
The camera used for these applications is BW. The camera does not “see” color. All tattile cameras can also be supplied as models with white light illuminators. In that case the cameras are equipped with color sensors and will be able to see the colors in plates. In some countries that is required.
Cost-effectiveness versus advanced functionality
The setup that is described here will work very well for security and parking applications. The focus of the application is on identifying the vehicle and hassle-free performance. VEGA Basic is a perfect device to support these applications. It offers high performance and a high degree of configurability against a fair price.
Of course additional functionality or features may be required. Maybe you would like to see high quality overview images with clear pictures of the vehicles. Or maybe you would like the camera to be able to automatically classify the vehicle and identify the bramd, color or model? In that case the Tattile VEGA 1 might be a good alternative.
And of course there are other applications with even greater demands. in some applications for tolling or police surveillance, you may want to be able to simultaneously monitor two lanes with traffic at really high speed. Tattile’s flagship product VEGA Smart 2HD may be the best choice for those high end applications.
If you would like to learn more, please contact us.