Determining Position and Speed through Pixel Tracking and 2D Coordinate Transformation in a 3D Environment

Abstract

This paper presents a methodology for determining the position and speed of objects such as vehicles, pedestrians, or cyclists that are visible in video footage captured with only one camera. Objects are tracked in the video footage based on the change in pixels that represent the object moving. Commercially available programs such as PFTrack tm and Adobe After Effects tm contain automated pixel tracking features that record the position of the pixel, over time, two dimensionally using the video's resolution as a Cartesian coordinate system. The coordinate data of the pixel over time can then be transformed to three dimensional data by ray tracing the pixel coordinates onto three dimensional geometry of the same scene that is visible in the video footage background. This paper explains the automated process of first tracking pixels in the video footage, and then remapping the 2D coordinates onto three dimensional geometry using previously published projection mapping and photogrammetry techniques. The results of this process are then compared to VBOX recordings of the objects seen in the video to evaluate the accuracy of the method. Some beneficial aspects of this process include the time reduced in tracking the object, since it is automated, and also that the shape and size of the object being tracked does not need to be known since it is a pixel being tracked, rather than the geometry of the object itself. Concept of 2D Coordinate Transformation The tracking of objects in video, also called motion tracking, can be a manual or automated process where, in an x and y coordinate system determined by the video's resolution, a discrete pixel, or series of

Mid-Range Data Acquisition Units UsingGPS and Accelerometers

“…The VBOX 20 Hz VB20SL3 -Triple Antenna (SL3) data logger with accelerometer was used for comparison with data recorded with Harry's Lap Timer™. The VBOX is an industry accepted data acquisition system that has been widely accepted in the accident reconstruction community for measuring GPS location, speed, acceleration in all 3 axes, yaw, pitch, and roll angles, heading, and elevation changes [18], [19], [20]. This unit is calibrated once per year to ensure accuracy.…”