A vehicle classification system based on microwave radar measurement of height profiles

We consider a new system for classification of vehicles. The proposed system uses the vehicle shape as measured by a microwave radar sensor as the main feature for classification. The sensor is mounted above the road surface (perpendicular to the ground plane), so that vehicles pass vertically below the sensor. The surface of a typical vehicle can be approximated as a finite number of planes, most of which (such as roof, bonnet and body) are nearly parallel to the ground plane. When a narrow radar beam from the sensor illuminates the vehicle from above, all the relevant scatterers on the vehicle surface are at approximately the same distance to the antenna and they can be lumped together as one dominant scatterer. Using signal correlation techniques, a high-resolution measurement of the sensor-vehicle distance is repeatedly performed during vehicle passage through the vertical radar beam. This time series of distance estimates forms the vehicle radar image a, which is used to create the vehicle feature vector to be used as input to the vehicle classification algorithm.