A.A. Kalinkevich, M.S. Krylova, V.M. Masyuk, V.N. Marchuk
Electromagnetic radiation of VHF band characterizes with high penetrability in vegetation and upper layers of ground. When the ground is exposed to radiation at an angle to the vertical by means of side-looking radar with synthesized aperture (SAR) in this waveband the backscattering coefficient depends not only on roughness of the ground surface but dielectric inhomogeneity of the upper layers of the ground too. One can expect that the main contribution to the backscattering is given by inhomogeneities with sizes commensurable with radar wavelength. Inhomogeneity structure in subsurface layers is a very complicated point in research. An attempt to investigate inhomogeneities by means both georadar and direct method of augering is made. As a result we obtain a confirmation that the upper layers of ground do have nonuniform structure, especially in a forest area. Analysis of spacial spectra of heterogeneities at different depths has shown that the spacial heterogeneity fluctuations indicated by georadar are concentrated at a depth of 1 meter. The further investigation has shown that the inhomogeneity pattern differs for two different forest areas. In case of forest with high backscattering it is observed more intensive spectral components in the range space commensurable with wave number of VHF channel of the SAR. One should consider the provided results as preliminary ones since it has been unclear up to date how and by means of which methods one can carry out the detailed investigation of dielectric inhomogeneities in the upper layers of ground in large forest areas.
Keywords: synthesized aperture, georadar, microwave physics, penetration, Inhomogeneity structure of ground surface