Patent ID: 9083856
Filing Date: 2015-07-14
Classification: G06K,G08G,H04N

Abstract:
1. A vehicle speed measurement method for identifying a violating vehicle, said method comprising: capturing a vehicle image utilizing at least one image capturing unit in order to estimate a speed of said vehicle via an automatic license plate recognition unit and thereafter locate and extract license plate character data from said vehicle image; calculating a license plate distance from said image capturing unit utilizing a physical character height from a reference point of said image capturing unit and a pixel character height generated by said automatic license plate recognition unit; generating a ground map that translates a distance of ground from said image capturing unit for each pixel in a field of view of said image capturing unit utilizing a calibration process; and implementing said calibration process by: configuring a hitch calibration target having at least two vertical risers with a plurality of rice shaped reflective targets spaced at an equal increment and a horizontal grid of reflective globes spaced at a known spacing; collecting a plurality of data points for each pass of said vehicle through said field of view of said image capturing unit thereby requiring fewer passes utilizing said hitch calibration target; and locating a center of said plurality of reflective globes by considering a known spacing and thereby calculating a center for each close pair and a height of said center as a function of distance and a x, y position; determining a license plate height from a road surface utilizing a position of said license plate in said field of view in association with said license plate distance to thereafter accurately estimate said vehicle speed based on said license plate height.