Automated extraction of weather variables from camera imagery.

Thousands of traffic and safety monitoring cameras are deployed all across the country and throughout the world to serve a wide range of uses, from monitoring building access to adjusting timing cycles of traffic lights at clogged intersections. Currently, these images are typically viewed on a wall of monitors in a traffic operations or security center where observers manually monitor potentially hazardous or congested conditions. However, the proliferation of camera imagery taxes the ability of the manual observer to track and respond to all incidents and the images contain a wealth of information that often goes unreported or undetected. Camera deployments continue to expand and the corresponding rapid increases in both the volume and complexity of camera imagery demand that automated algorithms be developed to condense the discernable information into a form that can be used operationally. MIT Lincoln Laboratory, under funding from the Federal Highway Administration (FHWA), is investigating new techniques to extract weather and road condition parameters from standard traffic camera imagery. To date, work has focused on developing an algorithm to measure atmospheric visibility and proving the algorithm concept. The initial algorithm examines the natural edges within the image (e.g., the horizon, tree lines, roadways) and compares each image with a historical composite image. This comparison enables the system to determine the visibility in the direction of the sensor by detecting which edges are visible and which are not. A primary goal of the automated camera imagery feature extraction system is to ingest digital imagery with limited site-specific information, such as location, height, angle, and visual extent, thereby making the system easier for users to implement. Many challenges exist for providing a reliable automated visibility estimate under all conditions (e.g., camera blockage/movement, dirt/raindrops on lens) and the system attempts to compensate for these situations. This paper details the work to date on the visibility algorithm and defines a path for further development of the system.