Evaluation of Road Condition in Dense Fog using in-vehicle Cameras

Fog is a complex atmospheric phenomenon. It is a visible mass consisting of cloud water droplets or ice crystals suspended in the air at or near the earth’s surface. Fog usually occurs by radiational or advectional cooling of moist air, resulting in a high concentration of microscopic airborne water droplets. Camera based methods are used to detect the presence of the fog level and object intensities in the video stream for the evaluation of the road condition using a approach called backscattered veil. Backscattering is the reflection of waves or signals back to the direction from which they came. It can be used to assess the presence of fog around the vehicle which is created by the headlamps. It aims at detecting fog when the vehicle is alone in absence of exterior public lighting. In this aim, a correlation index is computed between the current image and a reference image where the fog density is known. Scattered light does not simply disappear as if it was absorbed by smoke or dust. It simply propagates along different paths, some of which end up into the driver’s eyes. It results in an added luminance which impairs visibility by reducing contrasts. Applying backscattered veil detection technique for extracting the region where the obstacles found and analysis the same under positive environment.

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