"The latest off-the-shelf cameras with the most sophisticated software provide the most cost effective solutions."

Transport Data Systems designs and produces high performance image capture systems, optical character recognition systems and violation intermediate preprocessing servers to support a variety of applications. These systems provide the ability to capture and record license plates from stationary or moving vehicles. They also are useful in providing license plate inventory and vehicle security for the parking lot industry.

TDS license plate capture systems use high resolution digital cameras operating in the visible or near IR spectrum to produce high quality video images for manual or automatic license plate extraction. Asociated software module provides for the automatic plate detection, extraction of the numeric value of the license plate, image and plate number matching and self triggering.

TDS offers a complete line of servers to provide for local/remote OCR and manual image processing of violation data.

TDS offers a variety of license plate capture products, covering all areas associated with Toll Collection, Traffic Management, CVO Management, Parking and Homeland Security.

Principles of License Plate Capture and Recognition

The keys to a good license plate reader system design are:

Location of the Capture Zone

The location of the capture zone plays a major role in good VES system design. Direct sunlight on the capture zone can be very detrimental to the photo process. An ideal capture zone location is one that is completely removed from any changing lighting effects due to the sunlight. The amount of sunlight that falls directly on the capture zone is a function of the plaza design as well as the plaza orientation. In most cases the plazas already exist and therefore this portion of the design is constrained to the location of the capture zone with respect to the canopy. The key here is to locate the capture zone as near to the center of the canopy as possible, thereby reducing the time that direct sunlight may impinge on the image capture zone.

The capture zone should definitely be located in a portion of that lane that constricts the vehicle to a limited area. Putting it out beyond the end of the lane allows for too much lateral movement of the vehicle.

Location of the Camera

The camera should be located at a distance of 18 to 24 feet from the capture zone, though other distances can be achieved with the use of appropriate lenses. Ideally this location should be near the front of the lane at a height of approximately 4 feet above the ground. Putting the camera at a larger distance above the ground causes plates from a variety of trucks to be hidden by part of the truck body. The camera should be located at a distance of about 1 to 2 feet from the edge of the roadway.

Location of the Illumination

The capture zone illumination is critical and should be as near the source as possible. TDS will work with existing lighting and will add the appropriate additional lighting as needed.

Camera Resolution

Camera resolution is critical to the optical character recognition process. The use of a high resolution area scan digital camera provides the requisite resolution. The pixel counts should be approximately 125 pixels per foot in the horizontal axis and 100 pixels per foot in the vertical axis. This is consistent with a compressed image size of approximately 100 kilobytes for a 1300 by 1000 pixel camera.

Camera Triggering

In order to avoid loss of images due to vehicle movement, the triggering of the camera is important. Using a Traffic loop for this purpose is not recommended.

Camera Control

The camera control algorithms must be able to adapt easily to a variety of external light conditions. The objective is to provide for excellent visibility on the license plate itself. The use of advanced signal processing techniques can help to optimize the ability of the camera to provide this visibility.

Optical Character Recognition

The Optical Character Recognition capability provides a significant reduction in the amount of time required to process a single image. In high volume situations the savings in operator hours during the processing of the violations can result in enormous cost savings to the operator of the violation processing center. The success of the OCR process is very dependent on the quality of the images to be processed.

Advantages of the TDS solution

A good violation processing system is the product of a good system design. The design must take into account all aspects of the violation process.

The TDS approach considers each of the key factors discussed above. In this way TDS can assist the system designer in the implementation of reliable and efficient violation processing system.

For information about the TDS designs, please download the appropriate brochure.