Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2018, Vol. 15, No. 1, pp. 42-51
Specificity of bridges appearance in radar images
L.N. Zakharova
1 , A.I. Zakharov
1 1 V.A. Kotelnikov Institute of Radioengineering and Electronics RAS, Fryazino Branch, Moscow region, Fryazino, Russia
Accepted: 31.12.2017
DOI: 10.21046/2070-7401-2018-15-1-42-51
The mechanisms responsible for the fornations of the bridges appearance in high resolution radar images are considered in the paper. Schemes of signal propagation and re-reflection within the framework of geometric optics are given; practical manifestation of the backscattering schemes mentioned is demonstrated on the Sentinel-1A spaceborne radar images. Three bridges under consideration have different constructions (two suspension bridges and a truss bridge) and functional assignment (automobile and railway ones); the bridges are located at different altitude above the water surface. It is important to mention also that the observation days were selected in different seasons of the year in order to have different state of the water surface below the bridges. Image layover effects are discussed in details with respect to observation geometry and bridge design. Three main scattering mechanisms are delineated: single-bounce scattering from a bridge elements; double-bounce scattering including mirror-like reflection from water/ ice; triple-bounce with double participation of water/ice surface in scattering scheme. For the bridge located in a moderate climatic zone, a comparison of the signal backscatter in the case of clear water and ice covers beneath the bridge is made. The conditions ensuring appearance of higher order multi-bounce scattering are described.
Keywords: synthetic aperture radar (SAR), SAR image, bridges, multiple bounce, ray optics, scattering mechanisms
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