isolating the plate on the picture Plate orientation and sizing – compensates for the skew of the plate and adjusts the dimensions to the required size Normalization – adjusts the brightness and contrast of the image Character segmentation – finds the individual characters on the plates Optical character recognition Syntactical/Geometrical analysis – check characters and positions against country-specific rules The averaging of the recognised value over multiple fields/images to produce a more reliable or confident result, especially given that any single image may contain a reflected light flare, be partially obscured, or possess other obfuscating effects. The complexity of each of these subsections of the program determines the accuracy of the system. During the third phase (normalization), some systems use edge detection techniques to increase the picture difference between the letters and the plate backing. A median filter may also be used to reduce the visual noise on the image. Difficulties There are a number of possible difficulties that the software must be able to cope with. These include: Poor file resolution, usually because the plate is too far away but sometimes resulting from the use of a low-quality camera Blurry images, particularly motion blur Poor lighting and low contrast due to overexposure, reflection or shadows An object obscuring (part of) the plate, quite often a tow bar, or dirt on the plate Read license plates that are different at the front and the back because of towed trailers, campers, etc. Vehicle lane change in the camera's angle of view during license plate reading A different font, popular for vanity plates (some countries do not allow such plates, eliminating the problem) Circumvention techniques Lack of coordination between countries or states. Two cars from different countries or states can have the same number but different design of the plate. While some of these problems can be corrected within the software, it is primarily left to the hardware side of the system to work out solutions to these difficulties. Increasing the height of the camera may avoid problems with objects (such as other vehicles) obscuring the plate but introduces and increases other problems, such as adjusting for the increased skew of the plate. On some cars, tow bars may obscure one or two characters of the license plate. Bikes on bike racks can also obscure the number plate, though in some countries and jurisdictions, such as Victoria, Australia, "bike plates" are supposed