One of our most requested advanced analytic functions in video surveillance is license plate recognition or LPR. This is a software feature that can automatically match the license plate of an oncoming car with an authorized resident or guest list, so that cards, fobs, or even windshield tags are not needed for a vehicle to gain access. Note that some regions might use the term ANPR, which stands for Automatic Number Plate Recognition.
Our Most Frequently Asked Questions on LPR/ANPR:
What is LPR?
What is LPR?
LPR is an AI-powered, cloud-managed, highly accurate license plate recognition technology that works with standard ONVIF-compliant cameras and enables them to function as LPR cameras within a cloud VMS.
Will LPR work on my existing cameras?
Which stream of camera is used for LPR?
Full resolution stream is used for LPR - to image the license plate character clearly, you need a minimum resolution of 720P. Also in case of LPR, imaging is performed on a moving vehicle so
frame rate is also critical. Some of the more advanced LPRs are expected to deliver between 95 - 99% accuracy depending on the region and the quality of the license/number plates. The accuracy percentage is calculated based upon readable number plates from the camera view and assumes a quality installation and camera selection.
How much does it cost to use LPR?
LPR is typically offered as an add-on subscription service and is charged per LPR-enabled
camera. Depending on your subscription service, LPR may be offered monthly, yearly or as part of a multiyear subscription (3 yearly/ 5 yearly).
Will future LPR enhancements require new hardware or site visits to perform upgrades?
Typically no, LPR is AI-powered and part of a cloud VMS, which is continuously improved for higher accuracy without the headache of requiring new equipment purchases or site visits to update software or servers.
Can LPR be integrated with 3rd-party software applications?
Many cloud VMS do support 3rd-party integrations. This may vary greatly depending on the software and how willing the manufacturer is to develop integration partnerships.
Do harsh weather conditions and environments impact LPR?
Weather can impact LPR but it will still work in harsh weather conditions. However, a quality camera should be utilized and installed correctly to ensure license plates can be read from the camera view. As a general rule, if you can see the license plates with a human eye, then LPR should be able to read the plate as well.
Can my LPR camera also be used as an overview camera within the VMS?
No. During the day, the camera view and settings are similar for LPR and overview cameras.
However, at night the exposure of the camera is reduced so that crisp, clean images are
captured without any blurring due to motion. This makes the image look dark and nothing but
the license plate will be visible.
Which type of camera form factor is best for LPR?
A Bullet camera is the best choice for LPR due to higher focused power IR available with these and also the ability to align and focus the camera to the License Plate Imaging area.
● Dome cameras are not recommended. They can be used (and often are because they are
considered more vandal-proof). However, the IR performance is not ideal due to the lens
cover.
● PTZ cameras are not recommended. Due to the fact that PTZ cameras are used to view
different regions of interest, by design. Therefore, the camera could have been moved
and might be viewing the gate, which would lead to a failure on LPR reads.
What is the minimum camera resolution required?
Most LPR analytics need the camera stream to be a minimum of 1280 x 720 Pixels.
What is the maximum width of view for optimal LPR performance?
● If camera resolution is 1280 x 720 pixels, the camera can cover a maximum width area of 9 feet (3 meters).
● If camera resolution is 1920 x 1080 pixels or higher, the camera can cover a maximum width area of 20 feet (7 meters).
● Higher megapixels don't help unless you have a high power IR illuminator to illuminate the area at night as standard ONVIF cameras have the same IR illuminator for higher megapixels as well.
Are there any best practices to understand before installing LPR cameras?
It is best to have the camera tilted down between 20 to 30 degrees to avoid sunlight falling directly on the lens. The horizontal angle is best restricted to 20 degrees to avoid perspective error to acute viewing angle. The camera should be placed near the vehicle imaging area with a maximum distance of 15 feet (5 meters) to ensure clear imaging. It’s also important to ensure that the gate or parking barrier doesn’t block the camera view.
Is it true that LPR can work in conjunction with my access control installation and allow the License Plate to act as a Credential?
Yes, Some of the more tightly integrated video surveillance and access control packages have LPR with another credential option that is called License Plate Credential and can be enabled through eh cloud access control software.
Is there any additional hardware required to use License Plate Credential through my access control?
The short answer is Maybe. One we often run into is a USB to RS485 converter being required. The basic requirement for a USB to RS485 Converter is that it should support the Linux operating system and it should have three terminal pins (for D+, D-, and GND). A Bridge can support a maximum of up to 4 USB Ports. This is limited with the size of the USB to RS485 Converter being used as some of them are bulky and does not allow nearby USB to be plugged to the USB port and in that case, please use a USB extender.
Is there a need for a backup system when considering implementing License Plate Credential through my access control?
Yes, a backup should be considered when utilizing License Plate Credentials. This can be an additional reader from Brivo or an existing access control system. License plate reading can also be affected by external factors like rain and snow, which affects the reading and could impact proper opening of the gate. If there is a guard working, then they can perform an override and open the gate.
For more information on related video surveillance topics, get our special report: The 9 Biggest Mistakes Business Owners Make When Upgrading Their Video Surveillance Security
