An Energy Minimization Approach to Automatic Traffic Camera Calibration

We present a method for automatic calibration of traffic cameras. The problem is formulated as one of energy minimization in reduced road-parameter space, from which internal and external camera parameters are determined. Our approach combines bottom-up processing of a video to find a vanishing point, lines in the background, and a directed activity map, along with top-down processing to fit a road model to these detected features using Markov chain Monte Carlo (MCMC). Enhanced autocorrelation along the dashed lines is used in conjunction with a best-fit road model to find road-to-image parameters. To maximize both robustness to noise and flexibility (e.g., to handle cases in which the camera is looking straight down the road), a single-vanishing-point length-based approach (VWL, according to the taxonomy in the work of Kanhere and Birchfield) is used. On a large number of data sets exhibiting a wide variety of conditions (including distractions such as bridges and on/off-ramps), our approach performs well, achieving less than 10% error in measuring test lengths in all cases.