GV FAE Knowledge

Article ID: GV29-12-11-07-t
Released Date: 11/07/2012


Camera Installation
To increase the accuracy of license plate recognition, be sure to install the LPR cameras properly to capture the license plates with the correct image size, lighting conditions and camera angle. This document will first go over the installation guidelines and then show examples of images from cameras that are properly set up, as well as images that are not suitable for license plate recognition.

1. Installing the camera in front of the vehicle (Recommended): Install the camera straight in front of and above the vehicle as shown below.
   • The captured image should be filled with a full width of the vehicle.

     

     Screenshot_1.jpg (8.38 KiB) Viewed 4384 times

   • The distance between the vehicle and the camera should be within 5 to 50 meters; the camera height should be within 3 to 9 meters; the camera setup angle should be within 30 degrees.

     

     Screenshot_2.jpg (13.13 KiB) Viewed 4384 times

2. Installing the camera slightly to the side: If installing the camera straight in front of the vehicle is not feasible, the camera can be placed within 15 degrees to the left or the right as shown below. To avoid capturing unnecessary contents in the image, the camera should be installed in a higher position to capture the front part of the vehicle only.

   

   Screenshot_3.jpg (10.02 KiB) Viewed 4384 times

After installing the camera, make sure the height of the captured plate characters is approximately 30 to 35 pixels.

1. Capture a snapshot from the camera view of the installed camera. In the snapshot, the width of the vehicle should fill up the entire image.

   

   Screenshot_4.jpg (19.42 KiB) Viewed 4384 times

2. Open the snapshot in Paint and cut out the captured characters, e.g

   

   Screenshot_5.jpg (1.97 KiB) Viewed 4384 times

3. Paste the clipped image in another Paint file, and save it in BMP format.
4. Right-click the BMP file, select Properties and click the Summary tab to see the Height.

   

   Screenshot_6.jpg (18.42 KiB) Viewed 4384 times

   Tip:Besides camera installation, setting the camera to start image capturing upon motion detection or I/O trigger may also affect LPR results.
   • Motion Detection Mode: Recommended where false motions, such as from animals or people, are infrequent, or when false image capture is not an issue for you. The benefit of this mode is that the license plate image will always be captured.
   • I/O Detection Mode: False motion detection can be avoided and the CPU loading is lower.
   For GV-DVR LPR System, refer to Chapter 12 in GV-ASManager User’s Manual to see how to set up the detection mode. For GV-DSP LPR, refer to Chapter 4 in GV-DSP LPR User’s Manual to see how to set up the detection mode.
   

For detailed examples of suitable and unsuitable license plate images, see the full article.