6. Recommended Camera Position
A good ANPR engine can read the plates from images taken in various conditions. However, if you want to achieve
over 95% recognition rate with short recognition times, you have to calculate the position of the camera
accurately. The best position is if the angle between the camera axis and the direction of the vehicle movement is
minimal (see below).
The distance between the camera and plate is also important. If the camera is too far from the plate, the characters
may not be large enough for recognizing them. In this case, zoom-in until you reach the proper size. If the distance
is too short it may happen that a part of the plate is over the camera’s field of view (when the vehicle is near to the
side of the lane or the plate is not at the middle of the vehicle).
From the point of ANPR/LPR the most important is the size of the characters on the image. For English characters it
is recommended to have at least 16 pixel average character height, for Arabic or other special characters it is
recommended to have 20 pixel height (due to they are more calligraphic than the English characters). The too
large characters are also not suitable for ANPR, therefore try to avoid settings where the character size is greater
than 50 pixels in height. A line width of a character on the image should be at least 2 pixels.
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FreewayCAM Install Guide
