Void-layer detection and depth determination in runways based on GPR

Void-layer detection and thickness determination in runways are studied in this paper. Void-layer is thin layer whose thickness is very small (usually less than 1cm). Firstly, the void-layer can be detected based on its time-frequency distribution characteristic- S transform. This is the first attempt of S transform to be used in the void-layer detection of runways. In the same time, the depth of void-layer can be evaluated based on spectrum optimisation inversion method, in which the impulse pair in the time domain corresponding to the upper and bottom interface of void-layer can be extracted based on the EM wave propagation model and improved system identification method we have proposed in other paper. The simulation results demonstrate the proposed method is valid and the estimation error of thickness is within 5%.