Methodology for Georeferencing Roadside Pan-Tilt-Zoom CCTV Camera Views to Highway GPS Coordinates

Identifying the precise location of an incident is a critical component of traffic incident management. Most states and larger metropolitan agencies have deployed closed-circuit television cameras to verify the exact location of incidents received from motorists’ calls and facilitate incident coordination. Past studies have investigated positioning the nearest camera’s view on the incident using a camera-to-mile marker mapping methodology, where the views are positioned on the nearest mile marker to the incident. This approach is labor intensive, and the field of view may not capture an incident away from the mile marker. This paper describes a camera calibration process using orthorectified aerial imagery and publicly available digital elevation models and proposes a camera-to-GPS positioning methodology. This new methodology will allow for continuous positioning of the camera view to any GPS coordinate, either along the road or an adjacent ramp in view of an agency camera. Coordinates can be obtained from incidents identified by irregular paths of connected vehicles or connected emergency vehicles on scene. These techniques have been applied to 71 cameras in Indiana and used daily by traffic management staff. This paper concludes with a discussion of the limitations of the simplified geometric model used and improvements that could increase the accuracy of the proposed methodology at the cost of increased complexity.