How to Install License Plate Reading Cameras for the Best Accuracy
Automatic License Plate Recognition cameras (ALPR cameras) are an essential tool for access control, tolling, and parking management. However, achieving high accuracy LPR heavily depends on proper installation. Whether you’re setting up a system for a gated entrance, a toll gantry, or a parking facility, this guide will walk you through how to install LPR cameras for optimal performance.
1) Choose the Right Location
One of the most important factors in LPR accuracy is camera placement. If you’re dealing with a short approach lane, positioning the camera correctly is especially critical. Vehicles must have enough space for the camera to capture a clear image before reaching a license plate gate or checkpoint.
Key Considerations for Placement:
1) Minimize obstructions: Ensure an unobstructed view of the license plates.
2) Optimal distance: Inex ALPR cameras can read license plates from as close as 5 feet. However, shorter distances may result in harsh capture angles, potentially causing occlusions due to the curved shape of vehicles. When space allows, a distance of 30 feet from the barrier gate is typically recommended for installing rear-view ALPR cameras.
3) Optimal Angle: Angles under 25 degrees provide the best accuracy for license plate recognition. Larger angles can lead to occlusions, particularly when the license plate is mounted on a concave surface of the vehicle.
2) Mount the LPR Camera
Proper mounting is crucial for stability and accuracy. A poorly mounted camera can lead to shaky footage or misalignment, reducing the ALPR camera’s effectiveness.
Mounting Tips:
1) Secure the Camera: Use a stable pole, wall, or ceiling mount to minimize vibrations. If the camera is not mounted securely, it can drift over time.
2) Height Matters: For optimal performance, mount the camera 8 feet off the ground. This height provides a clear view of the vehicle while keeping the camera out of easy reach. Mounting the camera too low may extend its line of sight beyond the approach lane, potentially capturing license plates from passing street traffic. While this can be mitigated by adjusting the camera software to limit readable license plate sizes and by masking unwanted capture areas, proper placement is the most effective solution.
3) Angle Adjustment: Tilt, pan, and roll the LPR camera to get the license plate in the target area centered in the frame.
4) Weatherproofing: Ensure the mount is secure and the LPR camera cable is protected from rain using a drip loop. Without a drip loop, rainwater and ice can accumulate where the cables enter the camera, potentially compromising the water seal over time.
3) Adjust the Camera for Optimal Performance
Once the location is set, we need to adjust the camera position to maximize LPR performance. A well-configured camera can significantly improve accuracy, even in poor weather conditions or with fast-moving vehicles.
Camera Settings to Optimize:
1) Focus & Zoom: Ensure that plates appear sharp and readable. The license plates should be between 150 to 200 pixels wide in the camera view. Note that all Inex cameras have motorized focus and zoom, and thus this adjustment is performed via the camera web interface.
2) Exposure & Shutter Speed: Adjust the shutter time to reduce motion blur for moving vehicles and to get a clear, well-lit picture.
3) IR Illumination: The IR camera (infrared camera) is used to capture license plates in low or no light conditions. The IR camera will need to have a lower shutter time than the color camera.
4) Test and Calibrate for High Accuracy LPR
After installation, we need to thoroughly test the system. Drive different vehicles through the detection zone to confirm that plates are being read correctly at various speeds, lighting conditions, and driving styles. If you notice inconsistencies, the system may need to be tweaked for a specific type of plate or vehicle.
Final Checklist:
1) Plates are read by the ALPR system in both light and no-light conditions.
2) The ALPR camera captures plates clearly even when cars are moving at the fastest reasonable speed for the lane.
3) No glare or overexposure affects readability.
By following these steps, you can ensure that your license plate reading cameras achieve high-accuracy LPR performance, even in short approach lane scenarios. Proper installation and fine-tuning will maximize efficiency and provide reliable plate recognition for your security or traffic management needs. The Inex technical support team has decades of experience with ALPR installations in all types of locations and is here to assist you.