Application of radio ground-wave propagation theory to the tomographic imaging of ground surfaces

Radiowave propagation over ground has been historically studied for predict ing the radiated fields when the ground properties are known and the field has been well covered over the past hundred gears. In this paper, the theor y of ground wave propagation is applied to inverse problem of the tomograph ic imaging of ground surfaces. After the inverse problem is formulated, an iterative technique for solving it is illustrated. This is based on the min imization of the cost function of the measured and estimated scattered fiel ds produced by the surface under investigation in isolation. Numerical simu lation results are presented for the reconstruction of four different groun d features surrounded by sea water namely: 1) dry ground; 2) wet ground; 3) dry-wet mixed ground; and 4) dry ground with a central water pool. It has been demonstrated that the technique is able to reconstruct the distributio ns of normalized surface impedance of the isolated surfaces and, hence, the ir images. The iterative process can converge with a small number of iterat ions using the normalized surface impedance of sea water as the initial gue ssed values. However, better images can be produced using a priori informat ion. This study thus illustrates a new application of ground wave propagati on theory with possible applications in ground surface mapping, remote sens ing, target positioning and monitoring, and navigation.