A successful implementation of ALPR for parking requires consideration on various factors, including camera selection and installation. This article takes a closer look.
Automatic license plate recognition or
ALPR has various applications, among them parking access control management. A successful implementation of ALPR for parking, however, requires consideration on various factors, including camera selection and
installation. This article takes a closer look.
Increasingly, parking lot operators, especially those in Asia, are turning to ALPR for entry/exit management due to the convenience and smooth user experience it brings. To effectively implement ALPR for parking, though, several factors need to be considered.
“Setting up ALPR in parking access control requires careful consideration of factors such as lighting conditions, camera placement, and camera type. Adequate lighting is essential for clear image capture, while proper camera positioning ensures optimal angle and coverage of license plates. The choice between a regular camera with ALPR software and a dedicated ALPR camera depends on factors like budget, installation requirements, and desired accuracy,” said Kevin P. Shanmugam, Principle Consultant at A-SAT.
Type of camera
A main consideration facing parking operators seeking ALPR adoption is the type of camera to choose. A dedicated ALPR camera may be considered in this regard. “We recommend having an onboard ALPR camera plus a ALPR server for the highest accuracy result (99.9%). Operators hate to spend man hours on getting calls from customers who are stuck at the entrance/exit due to poor ALPR detection,” said Erina Chao, VP of Sales at Telexper International.
While ALPR cameras may have certain advantages, the type of camera to choose ultimately depends on the user’s own scenario.
“The specialized ALPR camera for the car park is the easiest to implement and the most economical compared to a full fledge smart IP CCTV surveillance system with video analytics deployed with VMS software,” said Ler Wee Meng, MD of Securevision. “There are specialized ALPR cameras that come with their I/O, and it is directly connected to the car park barrier arms. There are edge cameras with built-in ALPR analytics or normal cameras that are linked to video servers running VMS software. Which type is deployed depends on the extent, scope and budget.”
Nguyen Dinh Hiep, CEO of TECHPRO, cites other considerations to be made when choosing a camera for ALPR in parking. “Advanced surveillance cameras are used to endure not only the rigors of the weather – heavy rain, fog, or heat but also potential tampering or vandalism. IP67-rated cameras are dust-tight and can handle temporary immersion in water. Cameras with wide dynamic range (WDR), backlight compensation (BLC), highlight compensation (HLC) technologies capture clear and balanced images/videos even in some challenging light conditions,” Hiep said.
Illumination
Good
illumination is also key in reading the plates of vehicles entering and exiting parking lots. “ALPR performance can be affected by lighting conditions. Favorable lighting is necessary to support license plate recognition. If possible, using natural light during the day and artificial light at night and dark places,” Hiep said.
“Effective ALPR depends upon two key factors. The first is to capture the image of a license plate and the second is to read the image. To that end, lighting can help illuminate license plates but it can also create problems if the light is too bright or angled. Moreover, the ALPR software (OCR or optical character reading) needs to be able to interpret the license plate. In places like southeast Asia, this includes vastly different types of license plates that come from countries like Thailand, Malaysia, and Singapore,” said Jim Simon, GM for APJ at Quantum.
Camera placement
Finally, placement of the camera is also important. “Recognition of the license plate is more affected by the speed and approach of the vehicle. If the vehicle is coming into a straight narrow lane at a low speed of 10 km/hour, it makes recognition faster and more reliable compared with a vehicle making a turn in, or a wide road at a fast speed. External factors like rain and snow can also affect and in some situations, a shelter may be needed,” Ler said.
Hiep, meanwhile, provides the following guidelines on how the camera should be placed and installed.
“Thoroughly walk through the entire parking lot to note potential security weak spots and high-traffic areas, such as entrances, exits and areas with poor visibility. Use this assessment to create a camera placement map. Optimize camera placement to ensure comprehensive coverage of the entire parking area. Start by installing cameras at critical transition points such as entry and exit points, elevators, and stairwells to monitor the flow of vehicles and people. To prevent unauthorized access and tampering, position these cameras high enough to be out of easy reach. Additionally, for effective vehicle identification, it's important to place some cameras at the vehicle level for clear license plate recognition,” he said.