Episode 8: “Hey Maarten, what is ANPR and why is it popular?”
Maarten Mijwaart from SecIndGroup.com tries answering questions that are relevant to the security industry. This week’s question: What is ANPR? And why is it so popular?
ANPR (Automatic Number Plate Recognition) or LPR (License Plate Recognition) has become tremendously popular in vehicle access control installations over the past years. ANPR refers to cameras that are capable of reading license plates, usually on cars. These cameras use OCR (Optical Character Recognition) to convert an image into a ‘string’, the actual license plate information (characters and numbers). This can then be used as the ID for the vehicle in an access control system.
Keep in mind:
ANPR cameras often use IR (infrared) light to isolate the plate from the rest of the picture. With some of these cameras additional effort is needed to read license plates with red characters.
ANPR cameras often use reflection of plates to isolate them. Non-reflective plates, which exist in some countries, may be more difficult to read.
OCR engines often are optimized for specific countries. Make sure your required countries are supported in the library or engine that is installed on the camera.
When colors need to be identified, ANPR-cameras with white light need to be used.
When used with Wiegand-connected devices, the alphanumerical string needs to be converted to a number. Wiegand conversion may be an optional feature of the camera.
The ANPR engine (with OCR, support for specific countries, conversion, configuration, storage settings, etc.) can be embedded on a camera or it can be installed on a server. In the latter topology the computing power of the server is used, which can increase the accuracy and performance. The installation however may be more complicated and additional software licensing may be required. Cameras with embedded engines are usually very much suitable for access control installations.
Some cameras can operate standalone through the use of a local white-list. This may be a good solution if you are dealing with one vehicle entrance. When you have more it would make sense to save on admin work and use a centralized access control system.
If you are new to ANPR, we would definitely advise to run a pilot first. You will then experience first-hand the few things that require specific attention with ANPR, like installation height, prevention of blocking the view, dealing with vehicle speed, etc. etc.
ANPR vendors on SecIndGroup.com: Tattile