Analysis and Measurement of Water Emissivity for the Monitoring of Road Surface State

A traffic accident is caused by bad weather conditions like rain fall, snow or ice cover of road surface status. The microwave radiometer measures the natural thermal radiation from the terrestrial atmosphere and the road surface and it can detect the status of road by the measurement of emissivity. There are several reasons to use microwaves for remote sensing of road surface compared with IR or a visible camera. The most important reasons are their capability to penetrate clouds, fog, and rain with small attenuation. Additionally, microwave remote sensing is not dependent on the sun as source of illumination. The information observed by visible and infrared radiation mainly determines the molecular resonance in the surface layer of the soil, whereas the information observed by microwaves determines geometric and bulk-dielectric properties of the surface or volume studied. In this paper, the theoretical analysis of water emissivity and dielectric characteristics are investigated to monitor the water layer on the road surface. Theoretical calculation of water emissivity is derived and the result is validated by the experiment in indoor and outdoor.