Automatic Number Plate Recognition (ANPR) systems are used to read the number plates on cars in a number of aplpications.
We will see how ANPR can be used in a car park for automatic entry and exit of cars.
A sensor detects a vehicle and sends a signal to a microprocessor to instruct a camera to capture an image of the front of the vehicle (often an infrared camera is used to give a clearer image and for use at night).
- An algorithm is used to locate and isolate the number plate from the image taken by the camera. This algorithm also takes into account the size of the number plate and any damage or orientation ——————-> 3ACD123
- The brightness and constrast of the number plate is first adjusted (this ensures that the characters can be clearly read). ————-> 3ACD123
- Each character on the number plate is then segmented —-> 3ACD123
- Each character is then recognised using optical character recognition (OCR) software. The characters are converted into a string of editable text by the software.
- This text string is then stored in a database.
Once all this has happened, the car park barrier is raised and the motorist is issued with a ticket. The ticket shows the date and time of entering the car park.
When the motorist returns to the car park, they insert their ticket into a machine which calculates the car park charges. The payment is registered in the database.
The motorist then drives to the exit barrier and the ANPR system again reads the number plate and checks its database. If the number plate is recognised (and payment has been made), the exit barrier is raised.