Rolf Finkele

Polarimetric road condition classification and data visualisation

The automobile industry has been continuously involved in efforts to improve driving conditions and comfort. Therefore Daimler Benz is interested in finding new techniques to monitor the road traffic conditions in order to make the information available for other electronic on-board systems. For this purpose a full polarimetric, incoherent microwave radar system for Mueller-matrix measurements was designed. It works at 76 GHz, employing 5 Impatt oscillators and 7 Shottky detectors. Special software tools for classification and visualisation of the acquired data has been developed. The paper introduces this system and describes its functionality as well as the concept of the data processing software. Measurement results are shown.

Superposition of polarized waves at layered media: theoretical modeling and measurement

The detection of ice layers on road surfaces is a crucial requirement for a system that is designed to warn vehicle drivers of hazardous road conditions. In the millimeter wave regime at 76 GHz the dielectric constant of ice and conventional road surface materials (i.e. asphalt, concrete) is found to be nearly similar. Thus, if the layer of ice is very thin and thus is of the same shape of roughness as the underlying road surface it cannot be securely detected using conventional algorithmic approaches. The method introduced in this paper extents and applies the theoretical work of Pancharatnam on the superposition of polarized waves. The projection of the Stokes vectors onto the Poincare sphere traces a circle due to the variation of the thickness of the ice layer. The paper presents a method that utilizes the concept of wave superposition to detect this trace even if it is corrupted by stochastic variation due to rough surface scattering. Measurement results taken under real traffic conditions prove the validity of the proposed algorithms. Classification results are presented and the results discussed.