What is an ALPR or ANPR system?
What is ANPR?
ALPR is an acronym for Automatic License Plate Recognition and ANPR is an acronym for Automatic Number Plate Recognition. Both acronyms mean the same thing. We talked about ANPR before in this video. An ANPR system is a system consisting of cameras with software that are capable to detect and read license plates, convert the information on the license plate into a digital format and send the result to processing systems, like an access control system, a tolling system or a parking management system. ANPR or ALPR systems sometimes also are referred to as just LPR (License Plate Recognition).
How do ANPR cameras work?
ANPR cameras constantly monitor an area, like a road or a vehicle entrance. It will usually send out infrared (IR) light that will reflect on the license plates and that will enable the camera to find the license plate and isolate it from the rest of the image. ANPR cameras utilize a technology called Optical Character Recognition (OCR) to actually read the plate under almost all weather conditions, without the need for human intervention.
Most ANPR cameras will usually collect a number of frames (images) and automatically select the best frames to read the license plate. A score is usually calculated that represents the chance that the plat was successfully read. Tattile cameras also collect and provide additional data, like the estimated speed of the vehicle, the vehicle direction and the country of origin. Some of the cameras are even capable to classify the vehicle and recognize the brand, color and model.
The event of a vehicle passing is usually referred to as a transit. Transit-related output of cameras often consist of images (greyscale OCR image and colour contextual image) and METADATA such as the license plate, the date/time, GPS coordinates, etc. Images and METADATA are then sent out in various formats to multiple hosts: FTP Server, TCP Message, HTTP Post, etc.
Range of applications
ANPR system support all kinds of applications. ANPR is mostly used for:
- Free Flow tolling
- Axle Counting
- Stop & Go tolling
- Low Emission Zone
- Speed Enforcement
- Red light enforcement
- City surveillance
- Vehicle tracking
- Homeland security
- Parking access
- Parking enforcement
- Access control
- Railroad crossing monitoring
ANPR technology enables authorities to improve the security in urban environments and on roads. ANPR helps reduce and prevent crime.
What are the main components of an ALPR system?
In typical ANPR applications the following components often are used:
- ANPR cameras
- Optional external illuminators
- Optional triggering systems (Laser, Loops, etc.)
- RFID Readers, used sometimes in combination with ANPR.
- Lane Controller
- Server applications with databases with access rights and to store events.
- Optional additional video analytics software on the server or inside te camera.
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