Measuring vehicle speeds with an uncalibrated camera

A system including a processor and a camera, the system configured to:

• during calibration, capture a plurality of images of a calibration vehicle traveling at a known ground speed;
• locate a calibration image feature in an image of the calibration vehicle;
• compute an optical flow of the calibration image feature thereby determine a model between an image speed of the calibration image feature and the known ground speed of the calibration vehicle;
• during speed measurement, capture a plurality of images of a target vehicle traveling along a road surface at unknown ground speed;
• locate a target image feature in an image of the target vehicle;
• compute an image speed of the target image feature;
• and
• apply the model to determine the ground speed of the target vehicle from the image speed of the target image feature.

A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to perform a method comprising:

• during calibration, capture a plurality of images of a calibration vehicle traveling at a known ground speed;
• locate a calibration image feature in an image of the calibration vehicle;
• compute an optical flow of the calibration image feature thereby determine a model between an image speed of the calibration image feature and the known ground speed of the calibration vehicle;
• during speed measurement, capture a plurality of images of a target vehicle traveling along a road surface at unknown ground speed;
• locate a target image feature in an image of the target vehicle;
• compute an image speed of the target image feature;
• and
• apply the model to determine the ground speed of the target vehicle from the image speed of the target image feature.