Identification of the spatial impulse response of inductive loop detectors

The inductive loop detector (ILD), since its introduction in the early 1960s has become the most widely used sensor in a traffic management system. Magnetic signature of the vehicle collected from ILD may be used, among others applications, for high resolution vehicle classification or vehicle re-identification. The ILD is the example of sensor with aperture which means that the information about vehicle geometry is, “masked” in magnetic signature due to the averaging properties of ILD. Quantitatively this process is characterized by spatial transfer function (spatial impulse response) of the sensor. Recovery of information from the signal is conditioned by the knowledge of this transfer function. This paper concerns the estimation of spatial impulse response of inductive loop detectors. The correlation method and pseudorandom binary (PRB) signal was applied to find a solution to this problem. The method was verified for detector in scale, during laboratory tests. The achieved results are satisfactory and justifies the continuation of research aimed at application of the proposed method to ILDs embedded in a roadway and cooperating with the traffic parameters measurement systems.